Newbie to AR. Hello all.

I recently purchased Quickload software and it got me wondering about what the pressure limits are of modern rifles. Specifically, as it applies to me I was looking for Rem 700 and Savage actions. All less than 20yrs old.

Also wondering what tolerance do action have? For example, if I load my 30-06 to 60kpsi and the action is rated to a 65kpsi max, does that mean I can shoot at 60kpsi and not stress or fatigue the metal??

Thanks

You will not overstress your actions with unlimited shooting of any loads that are shown to be safe in at least 2 different manufacturers' reloading books. IOW check your loads in at least 2 different reloading manuals or sources and don't worry about overstressing anything but your fevered imagination(G).
Regards, Joe

Hey BISCUT, In a modern action a 30-06(60K) is built no different than a 280(60K) or a 270(65K). 60K in a 30-06 will run forever. You can even run your 30-06 to 270 pressures(65K) and run it forever.

Main reason I ask is I have a 30-06AI that really likes to be pushed hard with 200gr boolits.

No sticky bolt but the primer pockets wont last 5 loadings. Common sense would tell me that the load it toooo hot.

Makes me wonder what psi brass is made to tolerate. In this instance I was using Nosler brass. Good brass but it seems to be softer than Win brass. I think I'll give the Win brass a shot next.

You will find that red lining a rifle does little in real life except impresss the non shooter around the water cooler. The extra (some times) couple of hundred FPS that you get comes at a price that may be paid at an ackward moment. I'm not threatening smoking shards of steel sticking out of your head but you could have a case failure or such just as you were shooting at a trophy animal, etc.
How are you determining these pressure figures you're quoting? Also, are you using a Chrony as you stretch the book? If not, the powder you're adding may not be gaining you any or very little additional velocity.

If you simply want the additional velocity then IMO it's stupid to load hotter, just rechamber to a case with more capacity. If OTOH you're loading hotter because the group size seems to be shrinking as the powder charge increases, then that is probably OK IMO as long as you remember that some day things might(probably will) go very wrong indeed.

Benchrest shooters commonly load to the max but they also know that eventually one of their case heads WILL blow. Refer to the first sentence above, one of my acquaintances(NOT a Benchrester) insists on loading to the max and boy was he surprised when his 280 AI blew up! Some folks are just naturally stupid and he's one of 'em.

Some brass is harder than normal, some is softer, some has flaws, how can you tell in advance? Answer: load to less than the max and you won't ever hafta worry about it!
Regards, Joe

#1). Metals. You talk to an engineer and he/she will tell you that a well designed steel tool will last X. Used below "overload" and that can be almost indefinitely. At the same time, make the device out of aluminum and they can tell you within 500 or 1,000 cycles when it will fail. Metals have a track record and steel used in rifles safely has no well defined "fail point." Same with cars. Mom and pop put 100K on the sedan then Jr decides to "hot rod" it and !!

#2). When a gun "blows up," what is usually the problem, for one of many reasons HOT gas gets loose. "Blow up" is a bit "simple." Modern rifles work at 55K CUP. That equals temperatures of gas of 4,000 degrees. Don't recall if that was C or F. Doesn't matter. Cutting torches work at temps of 2,000. Gas gets out of the chamber and into the action and it is not "torn" apart, shattered, broken, more like "hot knife thru butter..."

The old Hornady manual with plastic binding under .270 Weatherby told of loads that tore apart Mauser actions (proofed to 80K CUP approx. post WW I) but were well contained by the Weatherby action with the 9 locking lugs... Days before the Vangards were available. NO doubt legal liability standards post WW II have also encouraged makers to be extra careful.

What all this means if that you want to be extremely sure you don't have hot gas get loose. Modern brass [AND primers are brass cups] holds O.K. to about 55K CUP. Guess why "reading primers" is stressed. Cup leaks and the gas gets out... Like chewing paraffin wax. First couple chews and it shatters and gets gritty but then you get it up to the temp of your body/mouth and it becomes "plastic" and chews just fine. You don't want your gun "plastic" and chewy or you will get chewed up. Luck.

Appreciate your answers. While I do like to see what a new rifle is capable of during initial load developement, I'm by no means a "speed freak."

My reasons for pondering keeping a hot load w. the 200gr Accubond is purely for the accuracy. I'm less into speed and more into accuracy. In facy I fell in love with the 6.8spc after building a few AR's. Enough so I am going to have a bolt gun made off a Rem 700 223 action. I mention this because the 6.8, although absolutely deadly on deer and pigs, is not a screamer at all. Just accurate and effective.

Yes I do use a chrony.

Modern actions are not the limiting factor.
The brass primer pocket is the limiting factor.

You can blow a case head and possibly lose your vision without damaging the action.

A very wise German machinist in SD gave some something to ponder. He told me to seriously consider the fact that while modern actions can handle high pressure without issue, the brass, which most likely has not been re-engineered since introduction, may be way behind in tolerable pressure limits.

It was this conversation with him that got me thinking about actions and their limits as well as brass.

quote:

A very wise German machinist in SD gave some something to ponder. He told me to seriously consider the fact that while modern actions can handle high pressure without issue, the brass, which most likely has not been re-engineered since introduction, may be way behind in tolerable pressure limits.

It was this conversation with him that got me thinking about actions and their limits as well as brass.

The wise old German is right: the limiting factor in a rifle action is the brass case.

The cartridge case is simply a gas seal. It is not supposed to carry load, and once ruptured, terrible things can happen to a mechanism.

I consider an action to be "strong" based on how well it supports the cartridge case. The more steel around the brass case, the "stronger" the action.

Brass for cartridge cases varies in hardness, and varies in hardness within the case. The more workhardened the brass, the “stronger” it is, and yet, the less ductile it becomes. So a hard case won’t stretch as far as a ductile case. Ductile brass will stretch, but it won’t carry much load before it ruptures.

If you notice, brass is thickest at the case head. In most rifle actions this is the part of the case that is not supported by chamber walls.

I know target shooters who load such heavy loads that in one firing the brass is not reloadable because they expanded the primer pockets.

Military rifle teams shoot loads that are unacceptably high pressure, at least for me.


These are pictures of brass I picked from the Army Marksmanship Unit and USMC rifle team shooters at Camp Perry. This was their long range brass.

Those gas leaks around the primers eat rings into the bolt face. It costs money to replace bolts, and that is money that I don’t want to spend.

They use new brass with crimped in primers. The crimp mainly serves to keep the primers in the case after the cartridge is fired. You cannot see in these picture, but I have had AMU brass where the pockets were so expanded that the primer could be tapped out on your hand.





You could ask: Is this safe?. Well it is risky. Both the AMU and USMC team have a lot more money than I, they can replace bolts with gas etch rings around the firing pin holes, and they can scrap weapons and parts that break or wear out.

It is so difficult to quantify safety. How much risk are you willing to live with, and will you accept the consequences of being wrong?.

If you notice, top shooters always wear safety glasses. Everyone should wear eye protection when shooting a firearm.

I took my 308 long range ammunition brass to five reloads before I tossed the cases. I did not have an increased bolt lift and I did not have leaking primers. I dumped the brass when the primers were too easy to put in the primer pockets.

A single leaking or pierced primer will cause me to cut my load. A sticking bolt lift will cause me to cut my load.

I want to take my short range rifle brass up to the point they fail by case neck cracks or body splits. That may be 10 to 15 reloads.

After reading all of these posts, I just want to say that my philosophy on maximum loads is that they destroy the throat much faster than would a middlin' or cool load. Given what barrels and installation thereof can cost, I'll rip along at 2900 out of my 300WSM as opposed to 3100 and be finding myself lookin' at a new barrel much sooner than I should...

let me tell you an Alan Hall story about pressure. Alan became the junior partner in Shilen Barrels with Ed when they left Dewey's & Shooters Corner back in the northeast part of the country. They went to Texas and started building match grade rifle barrels. Alan had always had a bolt action design floating around in his head. It became the Shilen DGA (damned good action).
To hunt deer in Texas you generally have to own ground or belong to a hunting club with a lease. He joins one in time for deer season.
Alan had built himself a pretty fine looking DGA in 308 Winchester. He's got a good load, and is talking with an engineer at Winchester about it. The engineer asks him to send him ten rounds or so to "look at". He does, and they pressure test them. The loads are developing over 85,000 PSI!! Alan said the primer pockets were not loosening up til about seven or eight reloads. He did opt to cut back the loads, just a touch.
There is only one way to safely work up past the (conservative) manuals. Buy an Oehler M43 pressure testing chronograph system. If you have loose primer pockets you are taking the brass from a solid to a "plasticus" state. I think that is the word. It has started migrating away from the pressure weak spot.

I wrote for Precision Shooting Magazine for about ten years. I made a lot of industry friends and learned a lot. Some of it was pretty scary.

Rich

The old Arisaka 38 bolt action is very strong.

The Remington 700 and the Savage 110 are some of the strongest actions out there.The Savage might be the safest.

The guys who tested brass expansion vs pressure say your upper limit is about 70,000 psi. This will vary with brand ,case design, lot, and usage.

Modern bolt action rifles are made to withstand ~150,000+ PSI. Brass begins to fail quickly after 65,000 PSI, with blown primer pockets occurring after one shot when you exceed 75,000 PSI. The escaping gases can cause eye damage, thus alway wear protective glasses or goggles when working up a load. Generally speading, if you can reload youR cases with firm primer pockets at least 3 times, you should be safe. Also, shoot these hot loads only a few times per year for hunting, otherwise for target practice load way down to increase barrel life. Regards, Aiu

quote:

Originally posted by Idaho Sharpshooter:
There is only one way to safely work up past the (conservative) manuals. Buy an Oehler M43 pressure testing chronograph system. ...

Hey BISCUT, I'd strongly encourage you to completely ignore this piece of information. ALL the HSGSs have a unique set of problems which can not be compensated for outside a Ballistics Lab.

As ws recently proved beyond all doubt in this Blind Comparison Test, the M43 got thrashed severely by good old CHE & PRE.

If you are seriously interested in controlling Pressure before it becomes a problem for you, then you want to use the never improved upon, for well over a hundred years, CHE & PRE Pressure Detection Methods.

For your "AI" cartridges, nothing works as good as EGE(Extraction Groove Expansion) & CHE. Both will indicate to you when Pressure is building to the point of Trashing Primer Pockets - before - you get to that point.

Best of luck to you.

What Hot Core said.

You don't (or rather shouldn't) care 2 beans about what the exact pressure is, it's immaterial. What you DO care about is whether you're about to exceed the limit of your particular brass and primer combination. This 'Do Not Exceed' limit will vary with the particular combination of components you choose and only actual case measurement will show the initial brass movement and quantify the results.

Remember that armchair calcs 'prove' that a bumblebee can't fly and that Airbus aircraft are safe. I can picture the bumblebee hovering comfortably as he watches the Airbus come apart in flight or auger-in because its computer overrode its manual controls. Actual results trump armchair calcs every single time....
Regards, Joe

Thanks for all the good info boys! This is a nice site with some very knowledgeable input.

In the end, with strong, modern actions, nothing matters but the condition of the cases. Not EGE, not CHE and not "measured" pressures.

If the brass holds up and the primers hold up, it's OK. You can tell when you are approaching max by the velocities.

Weaker actions are a different story. The only way to load those is to load to known safe velocities as given by the reloading manuals. The powder charge doesn't really matter. If the reloading manual shows a charge of 25 grains to get to 2200 fps max safe velocity in your 1890 cast iron special and you hit 2200fps with only 23grs, you had better STOP adding powder.

The weakest steel is stronger than the strongest brass. It is the cartridge case which is the weak link in the pressure vessel. Almost any modern action will easily withstand pressures that will either blow the primer or the case head. The question is "how does the action handle the erupted gas?"

If a load, even one which generates more pressure than is sustainable, doesn't damage the brass, then it will not damage a modern turnbolt rifle.

quote:

Originally posted by BECoole:
You can tell when you are approaching max by the velocities. ...

Really don't want to get into a fight with BECoole, but this information is "full of beans".

There is nothing associated with Velocity that tells you ANYTHING useful about what the Pressure "might" happen to be. Way too many variables involved with the Chamber, Bore and Cartridge.

This is an old hoodoo tale that just refuses to die. And has the potential to get folks into High Pressure situations when they believe they are at SAFE levels.

Chronograps at best do two things:
1. Stimulate the economy.
2. Occasionally tell the user the Velocity of a Bullet.

Best of luck to all you folks.

Now that the brass has been identified as the weakest link, what are the pressure limitations of brass???? Assuming "new" brass, are most, all, brass made to a certain spec? Kinda like SAMMI? Or are manufacturers left up to their own decisions on what pressures they build their brass to handle?

Idaho Sharpshooter

"There is only one way to safely work up past the (conservative) manuals. Buy an Oehler M43 pressure testing chronograph system. If you have loose primer pockets you are taking the brass from a solid to a "plasticus" state. I think that is the word. It has started migrating away from the pressure weak spot."


You are absolutely correct. I have a M43 and have done fairly extesive testing with it on numerous cartridges. Out of curiosity I loaded a couple different cartridges (.223 and .308W) up to where I had leaking primers. Pressures were definately in the "proof"+ range. It was also scarey to actually know what some of my previous loads based on CHE were also actually doing for pressure. The only two methods I've found not to give over max loads are most loading manual loads and loads developed using PRE. However, several max manual loads were still over the SAAMI limit but then I was using some different componants and a different rifle. It is always best to work up the load as all manuals suggest instead of just accepting a load (max or not) as a "good load.

As usual HotCore is wrong but then who can argue with a man who claims to have shot "thousands" of deer! You were, as usual, right on Rich.

Larry Gibson

quote:

Originally posted by Larry Gibson:
As usual HotCore is wrong but then who can argue with a man who claims to have shot "thousands" of deer! You were, as usual, right on Rich.

Hey larry, I just went back and looked at the Link provided above where the "Blind Test" was performed by onefunz and Kelbro. Amazingly, there were "ZERO" comments by you in that thread. Perhaps because it showed what I've said all along to be 100% true and factual - GLOAT.

A non-calibrated Haphazard Strain Gauge System used outside a Ballistics Lab environment = Reloaders Pyrite(aka Fool's Gold Good old, never fail, always reliable, always repeatable, inexpensive CHE totally STOMPED the worthless HSGS into the ground. And was done so by a guy who was basically "new" to using CHE.

And IS is as WRONG about his comment as he was about using a Wheatstone Bridge.

PRESSURE WAR!

Head for a foxhole BISCUT!

quote:

Originally posted by woods:
PRESSURE WAR!

The War has been won ( GLOAT ), but we are still making a few casualties as we clean up the mess.

Hot Core

"Hey larry, I just went back and looked at the Link provided above where the "Blind Test" was performed by onefunz and Kelbro. Amazingly, there were "ZERO" comments by you in that thread. Perhaps because it showed what I've said all along to be 100% true and factual - GLOAT.

A non-calibrated Haphazard Strain Gauge System used outside a Ballistics Lab environment = Reloaders Pyrite(aka Fool's Gold Good old, never fail, always reliable, always repeatable, inexpensive CHE totally STOMPED the worthless HSGS into the ground. And was done so by a guy who was basically "new" to using CHE.

And IS is as WRONG about his comment as he was about using a Wheatstone Bridge. [/QUOTE]

No, I didn't comment on that thread. It appeared the test was done using federal .223 factory ammo in a .223AI chamber. Let's see now; little cosistency with the measurements and the M43 recording a PMAX of 41K or there abouts. Well duh! Since you're the expert here why don't you explain to us how much pressure it takes to expand the brass cartridge case into the improved chamber? We must also consider that fireforming a factory load in an improved chamber always results in less velocity and less pressure. The M43 measured this, the CHE did not. Nothing to gloat over actually. While interesting, it was a rather poor test of comparing CHE measurements with m43 measurements. As I have mentioned all too often to you; I have measured the differnce between CHE and the results of the m43 with several different cartridge/rifle combinations using standard ammuntion in standard chambers. The results are always consistant with the M43. The results are not consistant with CHE as sometimes they are quite correct but other times they are horribly wrong.

The most recent test mentioned was with .223 "White Box" M193 ammo purchased at a Cabela's. In the test 21" barrel other M193 ammo (4 different lots of LC) which were tested at the same time under with the same barrel under the same conditions all produced 3200-3250 fps velocities with MAPs of 56-60K psi. Those velocities and MAPs are normal and is what is expected of 5.56 M193. The CHE measurements for those 4 lots showed 2 to be pretty close to correct and 2 showed no CHE (the 2 lots with the lowest MAP).

The real problem with CHE's inconsistancy reared it's ugly head when the Winchester "white Box" M193 was tested. The MAP as measured with the same M43 in the same barrel under the same conditions was 65,700 psi with the Peak pressure being 68,300 psi...yikes! The velocity average was 3351 fps....yikes! That velocity and the severely flattenned primers were good indications of high pressure. The pressure reading of the M43 confirmed it. The problem was there was no, nada, none increase in CHE measurements on any of the 10 cases fired.....no "gloat" but that is another ....yikes!

That is a good demonstration of how CHE is not reliable. What the "blind test" demonstrates in relation to the M43 vs CHE is pretty vague and thus I did not comment.

I'll leave you and Idaho to argue the "Wheatsone Bridge" concept regards fluted barrels. BTW; I tend to agree with you in that regard but have no proof one way or the other and have no dog in that fight as I could be convinced either way with sound scientific proof.

As to the "Pressure War"; you've hardly won as you've not even won a skirmish let alone a battle;-)

Larry Gibson

CHE is not all that and a bag of chips. It depends upon the hardness of the brass, the size of the chamber, and the number of times the brass has been fired. It doesn't work at all that I can tell for antique cartridges.

quote:

Originally posted by Ackley Improved User:
Modern bolt action rifles are made to withstand ~150,000+ PSI. Brass begins to fail quickly after 65,000 PSI, with blown primer pockets occurring after one shot when you exceed 75,000 PSI. The escaping gases can cause eye damage, thus alway wear protective glasses or goggles when working up a load. Generally speading, if you can reload youR cases with firm primer pockets at least 3 times, you should be safe. Also, shoot these hot loads only a few times per year for hunting, otherwise for target practice load way down to increase barrel life. Regards, Aiu

B, here's what you need to know about your action and the strength of your brass. If your using Quick Load, set you max PSI at 65,000 and chrono your rounds and don't exceed the velocity QL says you should be getting at that PSI, powder, bullet, barrel length setting, etc.

BUT ALWAYS, as your working up a load monitor for pressure signs such as stiff bolt lift, ejector marks, loose primer pockets, or measure CHE as Hot Core suggests. Hot Core has posted how to do this and he can guide you to his prior posts. You don't need to invest the money in a M43 system, which I and others believe lack a means to test for accuracy or standardize.

Happy and safe shooting, AIU

I'm not going to indorse any one system. But I will give you this. Some time back I wanted a system that could measure chamber pressure because in reloading PRESSURE is the only thing that matters when it come to safety of your loads.

So in the process of looking for a proper system I ran across the strain gauge system. Also found a few articles on how to build on at home using an O scope which I already have. Now the strain gauge manufacturers say the in each application the gauge must be calibrated to a known standard. that is the big kicker. Since strain gauges are glued to the barrel there is a little more then just some human error involved here.

All the variables that I could think of at the time were Barrel steel, Hardness, surface finish, Glue type, thickness of the layer of glue used, position of the gauge in relation to the case, position of the gauge in relation to the axes of the bore, Then you normal variables such as temp, humidity, etc.
When you examine what minute voltages we are dealing with you will understand how something as simple as to thick a layer of glue will throw your reading off in a huge way. Oh and then there's the amplification circuit that also must be calibrated as well.

When I added up the tolerances of the strain gauge and the amplifier circuit there was no way to get a decent reading.
CALIBRATION IS THE KEY. and none of the commercial pressure readers supplies you with calibrated ammo. Because we have not even talked about all the variables in the rifle yet. Chamber size, throat angle and length, true bore diameter. rifling profile. Simple fact is that outside a ballistics lab the strain gauge is nearly useless when it comes to chamber pressures in a system where the gauge is not permanently mounted like a piezo gauge.
Then it's still only good for your rifle on the day of the test. It's just a number and it means nothing unless you have something to compare it to CALIBRATED AMMO.

Therefor I choose the only method that has any consistent results..... I look at the case.
Now PRE and CHE are not the end all be all of pressure reading either. But they are a far cry from throwing darts blindfolded over your shoulder.
For PRE and CHE to work you need to examine your cases carefully and measure with a delicate touch. Measuring to .0002" is not easy I know I've been a machinist for a long time. And you can't use cheep junk micrometers either. How can you expect to get good reading from a $40 mic.
Good quality Starrett, Mitsutoyo or Brown & Sharp are the only way to go and they ain't cheep.
And to second hotcore statement Velocity is not an indication of pressure

quote:

Originally posted by BISCUT:
Now that the brass has been identified as the weakest link, what are the pressure limitations of brass???? Assuming "new" brass, are most, all, brass made to a certain spec? Kinda like SAMMI? Or are manufacturers left up to their own decisions on what pressures they build their brass to handle?

So far as I am aware, there are no spec standards for brass thickness or hardness -- in other words, it is left up to the manufacturer to determine what is appropriate for a given caliber.

This varies to some degree according to what the manufacturer expects of the brass. Certain calibers have traditionally been made with thick webs and strong heads -- the .284 Winchester is among them, as are the Ultramags and WSM series. Other calibers like the .30-30 have rather aneamic brass based on the theory that these are low-pressure cartridges.

By and large, a manufacturer builds all of its brass which is on the same head to essentially the same specs, ie., brass for a .22-250 will have a head identical to a .243, .25-06, .270, etc. right up through a .35 Whelan. Despite SAAMI pressure specs for the .257 Roberts and .280 Remington being (inexplicably) lower that most in this series, and the .270 Win being (again, inexplicably) higher, all of the brass from the same manufacturer will have an essentially identical head, and therefore, identical pressure resistance. This is not to say that different lots of brass from the same manufacturer may not vary -- they can and do, particularly in terms of hardness -- but they are intended to be the same.

So, what is the capacity of a brass case? Well, obviously it varies. The pressure capacity of a given case (and presumably its lot mates) can be determined by monitoring it for head expansion. Most judiciuos reloaders will back off of a load which begins to exhibit stretched primer pockets with only two or three reloadings. If I "need" (want) to push to what I consider the limits, I will accept a load that allows the brass to be reused for five loadings before the primer pocket becomes uncomfortably loose. In calibers which see a lot of volume of shooting, I'd prefer that expansion of the head not be a limiting factor at all.

This all applies to modern turnbolts or similarly strong actions. If you push brass to the point of failure with some old action from the 19th Century, you're asking to dig steel out of your face. Besides, most such actions are somewhat "stretchy" and case deformation (as opposed to failure) becomes a problem with pressures that exceed the action design.

Just MHO-I've found the best accuracy in my .308's to be well under max loads and I don't think a deer can tell the difference in 2-300fps....After blowing ejector rod housings off 2 Ruger .45 Blackhawks,I learned max is NOT better.

quote:

.After blowing ejector rod housings off 2 Ruger .45 Blackhawks,I learned max is NOT better.

Most people would learn that after one ejector rod housing

kcstott

The strain gauges are calibrated when you buy them. They are not generic but are made for specific applications. In the case of the strain gauges used with the M43 they are made specifically to measure the expansion and contraction of steel under pressure..The M43 is calibrated when you buy them. As to all of the other tolerances you mentioned the pressure devices the firearm and ammunition factories use must deal with them also. There are certain things that are assumed such as the elasticity of certain steels such as barrel steels etc. These are "calibrated" into the equations the computer uses or the user inputs the "offset". Since there are no instruments that are actually inside a case to measure pressure all pressure measuring instruments measure pressure through secondary effects such as expansion or compression of copper or in the case of strain gauges, steel. Bear in mind also that SAAMI and CIP both list the MAPs in round 1k figures. This is simply because pressure measurements down to the single digit are not accurate. The Oehler M43 measures them in round figures to the hundreds which is industry standard. This simply because all of the variables you mention are accounted for within the computations. This is the same as with the big boys’ lab instruments and is the same with the Oehler M43.

As to "calibration" of the instrument when attached to the strain gauge which is attached to the barrel; there is no such thing as "calibration" ammunition. That is a misnomer that is confusing even though used by some. What is used is "reference ammunition". This is simply a specific lot of regular ammunition that is noted for its consistency. Winchester and Federal are the current suppliers of "reference ammunition". The pressure measuring machines or the computations are not adjusted to equal the pressure of the of the reference ammunition. What is done is the reference ammunition is fired in their test barrel. The difference between the reference ammunition’s pressure and the manufacturer of the reference ammunition pressure is then noted. That difference then becomes the "offset" by which they then compare the newly manufactured ammunition’s pressure to.

Using reference ammunition is a simple enough procedure for any owner of a M43 to do. It is also a recommended procedure by Dr. Oehler. That is to simply fire similar factory loads to get a "reference" pressure. Not to hard to really figure out how it works with factory pressure devices is exactly the same way the use of “reference ammunition” works with a M43. In my particular case I also received specific pressure data and test information from Federal and Winchester (kudos to them) on specific lots of .308W ammunition I was testing. The “offset” difference between the factory psi and the psi as measured in 3 different rifles was well within the expected “offset” of the use of “reference ammunition”. Thus we can say that my M43 was “calibrated” just as the big boys do their pressure measuring machines.

Additionally in conducting the M193 ammunition test I did as posted above you will note that I used 5 different lots of M193 factory ammo. Four of those lots had normal psi and velocities that are expected of M193 from a 21" barrel. The fifth load (Winchester white box M193) gave high velocity and higher pressure. Obviously there is consistency and accuracy there with the M43 and the psi's as measured are probably very close to the factory measured psi's.

The problem was with the CHE measurements. The two lowest psi lots showed no CHE and the highest psi of 65,300 also showed no CHE. Under the theory of CHE there should have been considerable CHE with that highest psi load yet there was none. There in lies the problem with CHE; it is inconsistent and considering the PMAP of 68,300 psi there should have been considerable CHE yet there was none. Obviously CHE is therefore unreliable. As mentioned it may be used as an indicator but I would not rely on it as a sloe measurement of high pressure as Hot Core suggests.

Larry Gibson

Hey kcscott, You made an excellent post on the subject.

quote:

Posted by BECoole:
...It depends upon the hardness of the brass, the size of the chamber, and the number of times the brass has been fired. It doesn't work at all that I can tell for antique cartridges.

All of that is True. There are "Tricks" to using CHE & PRE, but for most people they are easy to understand and work with.

On the Antique Cartridges, PRE works and is the only thing that does. By the time you get any other Pressure Indicators, you are waaaaaay beyond the SAFE Pressure for them.

There is nothing better for the home Reloader to moniter Pressure than good old, never fail, always reliable CHE & PRE.

quote:

Posted by larry:
...was 65,700 psi with the Peak pressure being 68,300 psi...

The problem here is larry has never understood that he really doesn't know what the Pressure actually is, because he has never Calibrated the HSGS, uses guessed at dimensions for the Chamber and needs a Fudge Factor to correct for the actual Pressure, but he also does not know what the Fudge Factor needs to be. So, any PSI reading larry posts is Full-of-Beans.

quote:

The strain gauges are calibrated when you buy them.

Wrong again. They are not Calibrated, they are randomly, spot Tested for continuity. That only means an electrical current "should" pass through the Strain Gauge. This looks like some kind of ignorance originally spread by dunceton.

quote:

As to "calibration" of the instrument when attached to the strain gauge which is attached to the barrel; there is no such thing as "calibration" ammunition.

And Wrong yet again. SAAMI has the responsibility of controlling and distributing Calibration Ammo(aka Reference Ammo) to the Ballistic Labs. Once it is fired in a HSGS, then the Fudge Factor(aka Correction Factor) is able to be determined. By using the Fudge Factor, the Test Labs are then able to think of their HSGSs as actual SGSs.

quote:

Using reference ammunition is a simple enough procedure for any owner of a M43 to do. It is also a recommended procedure by Dr. Oehler. That is to simply fire similar factory loads to get a "reference" pressure.

Still WRONG. The problem here is that the actual Pressure of the Factory Ammo is " unknown ". Due to that minor problem, the Haphazard SGS user is only flim-flamed into thinking he has mysteriously calibrated the System - with an " unknown ". I seriously doubt Dr. Oehler used those words, but if by chance he did, then he is seriously WRONG!

quote:

The two lowest psi lots showed no CHE and the highest psi of 65,300 also showed no CHE.

I actually believe larry was unable to get a CHE measurement. There is no doubt in my mind he is doing it incorrectly and never attempts to actually understand CHE nor PRE. Then he comes in making statements that it doesn't work. This is simply a situation of needing to know who is doing the posting and understanding his mental state.

Hey BISCUT, how do you like the AR forum so far? Me, I used to come here all the time for excellent advice and soak up all the knowledge many members here had to offer. Not so much anymore, most threads turn into a long drawn out pissing match about pressure, strain gauges, PRE/CHE etc. Or you get hammered for something as simple as asking about an AI conversion.

Good Luck!

Stevo (& WOODS of course) you'll always be the bomb for me on that other site.

So far I have found a lot of good info. But can certainly see what you mean. Others opinions of AI don't bother me at all.

In fact AI user posted some really good info on using QuickLoad to get at 65kpsi and see what velocity is compared to what QL says. Seems pretty sound and reasonable to me.

I certainly need a average Joe way to gage pressure.

Hot Core

If you're going to constantly pout your inaccurate drivel you could at least contact the manufacturers and ask them what they do.

You once again demonstrate your ignorence at understanding and inability to read. You insinuate that through the use of reference ammuntion the pressure machines are changed to read the correct pressure. This isn't so. They are used just as I said, the reference ammunition just gives them a "reference" to what their machine gets for pressure vs what the manufacturer of the reference ammunition got for pressure. The difference is called the offset and is factored in. You really should go kill another thousand or so deer and then get back with us.]

Perhaps you should contact the manufacturer of the gauges I use and discuss the "non-calibration" of their product. I currently have 23 firearms with strain gauges attached for pressure testing. They range from the .22 Hornet up through the 45-70. I've just recieved 10 more strain gauges to apply to other firearms/cartridges to expand my experience and knowledge. Each of tMarked as to specific lot and batch

The gauges come from the manufacture calibrated as to;

Grid reference in ohms
TC of gauge factor %/100C
Gauge factor at 24 C
Transver sensitivity
Thermal output coeficients for a specific steel

That information is provided for each gauge. I recently discussed this with the factory tech rep. He was kind enough to send me all the technical data available on his companies products. He was quite humored when I discussed your insistance on a "alack of calibration" of their gauges. He mumbled something about the world being full of uneducated idiots refering to you. I couldn't help but to agree.


SAAMI does not have the "responsibility to distribute "reference ammunition. SAAMI is a voluntere organization and I'm sure many here would be surprised as to how many of the big name firearm and ammuntition companies do not belong. Reference ammuntion is currently sold by Winchester and Federal with the stuff being sold by Winchester. All you have to do is contact their sales department and be ready to spend big bucks for the reference ammunition. All it takes is money. Once again Hot Core, you spout BS trying to impress those that don't know. Sorry, no cigar.

quote:

Using reference ammunition is a simple enough procedure for any owner of a M43 to do. It is also a recommended procedure by Dr. Oehler. That is to simply fire similar factory loads to get a "reference" pressure.

Still WRONG. The problem here is that the actual Pressure of the Factory Ammo is " unknown ". Due to that minor problem, the Haphazard SGS user is only flim-flamed into thinking he has mysteriously calibrated the System - with an " unknown ". I seriously doubt Dr. Oehler used those words, but if by chance he did, then he is seriously WRONG!

Again you failed to read. The pressure of the factory ammuntition was known, Winchester and Federal supplied me with the test information of the specific lot I was using. Again your ignorance at comprehending what is so easily read is astounding. Do you need glasses? Amazing how you found the time for education while killing all those thousands of deer. Yet you question Dr. Oehler. That's pretty bold for a one eyed old fat man, eh?

quote:

The two lowest psi lots showed no CHE and the highest psi of 65,300 also showed no CHE.

I actually believe larry was unable to get a CHE measurement. There is no doubt in my mind he is doing it incorrectly and never attempts to actually understand CHE nor PRE. Then he comes in making statements that it doesn't work. This is simply a situation of needing to know who is doing the posting and understanding his mental state.[/QUOTE]

"Mental state"...oh now that is choice isn't it. Can dazzle us with your uneducated BS anymore so you want to attack the "mental state" of those who disagree. Sorry Hot Core but almost every one sees you insistance on CHE as the holy grail know otherwise. As long as you continue with your rediculous claims of its accuracy I shall continue to cahllenge you and provide factual information to those who may care to read theses posts. However, most have seriously grown very tired of your outlandish claims and refuse to read them anymore. Perhaps that should be a clue to you and it would be a respite to me.

Larry Gibson

And don't forget that maximum pressure will change...

Several years ago I began using 24 grains of VARGET with Sierra's 80 grain MatchKing in an AR15 for 600 yard shooting. The bullet was seated to get a 2.55" COAL--longer than magazine length--for single loading. This is not supposedly a hot load.

After 1200 shots, with this and my short range loads, I began to blow primers once in awhile or experience gas leaking around the primer. It turns out that repeated firing will build up a powder residue just ahead of the throat and that will raise pressures. After some JB, everything returned to normal, but not for long. Now I JB more often and I have cut the charge.