i have worked up a load for my kimber 7/08 that according to the books is over max., but the cases are not showing excess pressure signs.the primers are flat-flat but no primer pocket expansion etc. my question is calculation of pressure. is there a web site or program that can calculate approximatley how much pressure that i am producing?

B H

No.

However, the correlation between velocity and pressure is very strong: if you are exceeding book velocity, you are extremely likely to be exceeding book pressure.

You can also estimate your load with a internal ballistic software program (such as Quickload), but all you get is an estimate, not a calculation of what is going on in your rifle. If you bootstrap Quickload (that is, use observed velocities to change the parameters in the simulation so it predicts the results) it can be very, very accurate -- but not perfect.

A good alternative is to spring for a strain gauge, and apply it. This will give you a direct measurement of the actual pressure, although there is some noise in the signal, and the number you read on the display is not 100% exact.

However, it is a direct measurement, and much better than reading-the-tea-leaves method of looking, measuring, licking, or whatever the brass..... Measuring the brass is a good way to get evaluate the state of the brass, but is only very loosely correlated to the pressure it it has been exposed to. HTH, Dutch.

Dutch is right on the money.

I have Quickload and a strain gage system and I thoroughly enjoy playing around with these toys, but both will occasionally lie to me. On the other hand, a $75 chronograph rarely gives a bad reading, and when it does, it's usually obvious that it was bad.

If your velocities are below book velocities for the same barrel length, then your pressures are probably OK. If your velocities exceed book velocities then your pressure probably exceeds standard pressures, too. There is no magic way to increase velocity without increasing pressure.

Due to the sloppy chambers on mass produced rifles, it is not unusual to require an extra grain or two of powder just to bring the pressure and velocity up to book levels. A chronograph and a loadbook that lists the pressure for each load (like the Hodgdon manual) will keep you in the safe and sane zone.

Kimbers use a SAAMI chamber and are pretty consistent. The difference may be explained by a) excellent barrel on that Kimber
b) slower lot of powder
c) slightly larger diameter lot of bullets
d) atmospheric anomaly

bounty hunter

Their are a number of programs that will calculate pressure data. One that comes to mind off hand is "Load from a Disk". I think if you search the internet you can find a "demo" copy of the program. It isn't to much to purchase if I remember right.
However, with that said, Reloading data from the manuals is usually right-on. Besides that you rarely get the best groups from "MAX" loads, several hundred feet per second less than max. is usually much more accurate and it's a whole lot easier on the rifle and barrel. If you wanted a "MAG" you should have bought a 7mm Rem Mag. or 7WSM or any number of high velocity cases. The 7/08 is a sweet shooting, low recoil, accurate cartridge, capable of taking just about anything you'd like to hunt. With a few exceptions!
If you don't push it, the rifle should last a life time.
Have fun, but don't push it. Life is too short.

Ralph, EVERY rifle manufacturer keeps their chambers within Saami specifications....

Kimber may have fewer "loose" chambers than the average maker, but unless they hammer-forge their chambers (and they don't), they, too, are subject to the results of reamer wear. They might throw their reamers away a little sooner, but they surely do not use a new reamer for every chamber.....

All that aside, throat length has much more influence on pressure than chamber dimensions. FWIW, Dutch.

quote:

Originally posted by Dutch:
Kimber may have fewer "loose" chambers than the average maker, but unless they hammer-forge their chambers (and they don't), they, too, are subject to the results of reamer wear.

"You can always tell a Dutchman, but you can't tell him much."

. . . . but I'll bet I can tell him this much: As reamers wear, the chamber gets tighter, not looser. Sloppy chambers come from the first chambers cut with maximum size reamers, not the last ones, which are cut with worn reamers.

Typical manufacturers start with reamers that are as large as SAMMI specs will allow (and, I suspect, sometimes larger) so that they can get the maximum number of chambers from them before they wear below specs. Higher-end manufacturers will forgo the economy of getting lots of chambers out of a reamer in order to make each chamber closer to SAMMI minimum.

If you're not showing signs of pressure other than a flatness of primers and the primer pockets are not enlarging, extraction is fine and the cases are fine I'd guess the load is ok for your rifle.

The above post by Dutch is a very good reply and the use of a chronograph is a big help in load development. They're not expensive and can be a big assist.

The comments about buying a magnum if you want magnum performance is also excellent. Your 7-08 will perform as good 100'/sec slower and you'll have a very valuable piece of mind.

quote:

However, with that said, Reloading data from the manuals is usually right-on.

Really.So when two manuals list identical loads and barrel lengths but the velocity varies by over 100fps,which one is right?Or when the maximum powder charge with identical components varies by 4 grains from manual to manual,which one is right?The truth is that the people producing the manual do not have your rifle or your lot#s of components so it is very unlikely that your chamber pressure will be the same as for the test rifle listed in the manual.As such not all loads listed in reloading manuals will be safe in your rifles and just because your powder charge exceeds the powder charge listed in the manual ,does not mean that your chamber pressure is excessive.The same can be said for chronographed velocities.You can take two rifles with the same barrel length and one may produce 100fps more than the other while showing no pressure signs and having very good brass life.The other rifle may show pressure signs and have very short brass life if you attempt to load it to produce the same velocity as the first rifle.Chronographs measure only velocity which which can't accurately be directly converted to chamber pressure.If you really want to measure chamber pressure accurately you need to use other equipment to do so.

that is the reason that i am shooting this load, because it is soooo acurate. the velocity is right where it should be for this powder charge. i have looked on several other reloading websights and have observed similar loads (even 2grns more than mine) published, but still all are above the books.again if i had major pressure signs i wouldn't even consider this load, this is just a curiosity thing for me to know what the pressure actually is

B H

quote:

Originally posted by bounty hunter:
but the cases are not showing excess pressure signs.the primers are flat-flat but no primer pocket expansion etc.

I'm always puzzled by people who are puzzled by questionable pressure, and you've already started to answer the question yourself when you state "but no primer pocket expansion".

If you are shooting a modern turnbolt, then the brass case is by far the weakest part of the pressure containment system. Marginally excessive pressures will not cause a brass case to fail instantly and catastrophically, but rather will, over the course of one or more firings, stretch the case beyond its useful limits. This will manifest itself in either swelling the head area to the point that it will not reenter the chamber, or by the primer pocket loosening to the point that it is obvious that its friction grip on a newly seated primer is insufficient.

Provided your cases are not swelled enough to fail to reenter the chamber (using neck or partial sizing only), simply fire one single case with the same load repeatedly until there is some indication of primer pocket fatigue. If you can use the same case for several firings, then your pressures cannot be considered "excessive", since "excessive" is only reached when the case cannot be reused repeatedly.

However, I also agree that if velocities are disproportionate to the amount and type of propellent being used, then there has to be some suspicion about pressure. On the other hand, I have owned guns with what most people refer to as "fast" barrels that may yield 100 fps more than expected and still meet the "repeatable loading" test.

Factors like freebore, interior barrel finish, and even bullet jacket metallurgy can cause significant variations in anticipated versus real world velocities.

quote:

Really.So when two manuals list identical loads and barrel lengths but the velocity varies by over 100fps,which one is right?Or when the maximum powder charge with identical components varies by 4 grains from manual to manual,which one is right?

Most likely both!
Could be the natural variation between two powder, brass, primer, or bullet lots. Then again the chambers and barrels of the two different test beds aren`t likely to be the same.
Then again most of the data found in manuals is for the manual writers product. The data for a 150gr 308 load in Noslers book already has a different bullet with different geometry, and hardness then Hornadies bullets in their manual. Same wgt & style but not the same bullet.
Remember the data in the books isn`t cut in stone it`s just a recommendation as to where to start your load and where to expect to find the max along with predicted results. They also stress that changing ANY component negates the accuracy of the data.

quote:

Could be the natural variation between two powder, brass, primer, or bullet lots. Then again the chambers and barrels of the two different test beds aren`t likely to be the same

My point exactly.No reloading manual can possibly be "right on" for every gun or lot# of components which is contrary to the statement that I quoted and replied to.

If you are shooting a modern turnbolt, then the brass case is by far the weakest part of the pressure containment system. Marginally excessive pressures will not cause a brass case to fail instantly and catastrophically, but rather will, over the course of one or more firings, stretch the case beyond its useful limits. This will manifest itself in either swelling the head area to the point that it will not reenter the chamber, or by the primer pocket loosening to the point that it is obvious that its friction grip on a newly seated primer is insufficient.

Provided your cases are not swelled enough to fail to reenter the chamber (using neck or partial sizing only), simply fire one single case with the same load repeatedly until there is some indication of primer pocket fatigue. If you can use the same case for several firings, then your pressures cannot be considered "excessive", since "excessive" is only reached when the case cannot be reused repeatedly.
[QUOTE] _______________________________________________________________________________________________________________ Make sens,probably the best way to check out pressure...

quote:

Originally posted by bounty hunter:
i have worked up a load for my kimber 7/08 that according to the books is over max., but the cases are not showing excess pressure signs.the primers are flat-flat but no primer pocket expansion etc.

Hey BH, Those are some good Pressure Indicators, but "flat-flat" is normally bad and "no Primer Pocket Expansion" might or might not be good. The Primer Pocket Expansion can be misleading if the Caseheads are too hard.

quote:

my question is calculation of pressure. is there a web site or program that can calculate approximatley how much pressure that i am producing?

Absolutely. Only problem is the Internal Ballistic Programs are Mathmatical Models that are not able to adjust their output data for the variations in your Chamber and Bore dimensions. But, they are one more Pressure Indicator to watch.
---

However, the correlation between velocity and pressure is very squirrely: if you are exceeding book velocity, you are might or might not be exceeding book pressure. Just depends on the specific Cartridge Components and the Chamber/Bore dimensions.

One of our AR members, asdf, recently PMed me about an article John Barsness had written concerning a 25% rise in Pressure just by swapping from a CCI Primer to a Winchester WLRM. Apparently Mr. Barsness has access to a Piezo Pressure Testing device which was barreled for a 300WinMag.

So as to shorten the discussion, Mr. Barsness noted:
2920fps at 55,800PSI with CCI Primers
2991fps at 70,100PSI with WLRM Primers

And asdf also mentioned he had seen similar increases in the A-Square Manual.

So, the folks that think a Chronograph is always a reliable Pressure Indicator are apparently unaware of things like this. As you can clearly see, simply using a different Primer can create a situation where using Velocity alone as a Pressure Indicator is Full of Beans.

Another poor alternative is to spring for a strain gauge(HSGS), and apply it. This will give you a Second Hand measurement of the actual pressure, and there is always variation in the output, the number you read on the display is not 100% exact.

There are a couple of significant problems with HSGS devices. Things like the cost, poor ability to get accurate Chamber Wall Thickness measurements, applying the Strain Gauge(which is always in the way and makes the firearm look like a Rube Goldburg Project), needing to carry a Laptop to the Range and worst of all, there is no readily available source of Calibration Ammo. And since you can't Calibrate it, any data it provides is suspect.

That brings you to the very best Pressure Detection Methods ever devised, good old time proven, never improved upon, Case Head Expansion(CHE) and Pressure Ring Expansion(PRE).

Measuring the Case Expansion is simply the very best way to get evaluate the Pressure, because you do it in comparison to Factory Ammo. It is closely correlated to the First Hand Pressure the Case has been exposed to.

A few additional benefits are:
1. You use simple inexpensive 0.0001" Capable Micrometers which 99% of all people find easy to use(there are a couple of exceptions I can think of, but no need to beat them up). They are precision measuring instruments which allow you to obtain First Hand Pressure information instead of the haphazard Second Hand strain gauge stuff.
2. The Mics are easily Calibrated and the HSGSs are not.
3. No need to hose-up your firarem with a Strain Gauge and have wires dangling off of it.(Really cute!)
4. No need to take incorrect Chamber Measurements, enter them into the HSGS electronics and "hope" you will get anything at all useful.
5. The Mics are easy to carry to the Range, unlike juggling around the HSGS electronics and a Laptop to run it.
6. The Mics can be had for $20 in comparison to the cost of the HSGS and a Laptop($2500?)
7. And best of all, the Mics provide excellent useful Pressure Information that will let you know without a doubt if your Reloads are SAFE.

---
A non-calibrated HSGS=Reloaders Pyrite(aka Fools Gold)

Best of luck to you bounty hunter.

Nothing like saddling up your horse named "Agenda", applying the spurs and hoping the Indians show up show you can shoot at 'em, huh, HC

Bounty hunter,
Let me try to answer your question another way. In the course of experimenting, I often accidently end up with loads that run 60,000 - 65,000 psi, sometimes higher, as measured with a strain gage system. This exceeds the SAAMI spec for the cartridge in my test mule, the 30-06. Some of the brass has probably been reloaded 50 times, since I don't throw away brass until the neck splits (due to the use of an M-die). Yet this particular rifle has never seperated a case or loosened a primer pocket or flattened primers or had a sticky bolt or misbehaved in any way until primary pressures exceed 70,000 psi and usually not 'till 75,000 psi, and not always then.

An optimist would conclude that 65,000 psi is perfectly safe in my rifle, since brass lasts forever and you're not going to hurt a good bolt gun at 65,000 psi.

A conservative would conclude that I should religiously stick to loadbook data since this gun provides no "signs" to warn of high pressure right up to the point where cases come undone.

My take is that, yes, a good bolt gun can safely run at 65,000 psi, but I'm here to tell you that it doesn't take much to push a 65,000 psi load into the red zone ..... a different lot of primers or powder, a different barrel condition, an exeptionally hot day, a powder measure that occasionally throws a few extra tenths of a grain, etc..

Do I want to run right on that ragged edge? Heck, no. A 30-06 loaded to 60,000 psi will do anything that I need to do, while providing a comfortable margin for error.

point well taken. one more time though. i am not concerened about the safety of this load at this time. it is o k. i was wanting to calculate the pressure to use as a learning curve for future use, but i believe that you have brought up the one big thing that i didn't consider, and that is the pressure can change drastically with just a small change ie; primers and the like. my thought process was centered on strictly powder charge and keeping all other factors constant. i know this thread took the position that i was concerened about the safety of this load witch is not the case. my appologies to anyone who misunderstood.

B H

Ok, not to beat a dead horse, but pressures can also change with temperature. I worked up a load that seemed ok with 3 shot groups. Later while shooting the same load I got excessive pressure signs after firing about 8 rounds relatively quickly. The barrel was pretty hot, but not excessively so (probably about 120 degrees). I got distinct pressure signgs (brass showed image of ejector hole on base and bolt handle lift was a bit sticky). Primers looked fine BTW.

I let the barrel cool between shots and got no pressure signs from a couple of subsequent rounds. I ended up pulling the rest of the loads and made a note in my book to modify the load. It was the most accurate load up to that point too.

As Hot Core mentioned, there is documented evidence (taken on piezo benches) that primers can completely screw up the relationship between pressure and velocity. I can't explain this effect, but the evidence is in print for all to read.

It appears the WLRM primer should be reserved for special powders, probably the slower ball powders from Win. Most other primers don't give that great a pressure change. Still, you must be wary if you have changed any components from those shown in the load books.

As for primers, the A-Square manual demonstrates that primers show not pressure, but how well your rifle is supporting the primer. They have a picture of a standard primer that took nearly a proof load and looks normal. You cannot gauge true pressure from a primer.

If you're meticulous, a strain gauge can get you the true pressure, but you must be careful. If you have a standard cartridge, use the same components shown in a good load book and keep the fps on the chronograph below what they show.

Yes, different load books can show different fps for a given cartridge, but those two load books may well have used different bullets and/or primers, both of which can effect pressure.

Get a chronograph at the very least, and knock a few % in fps off the book value. You'll be safer, and your target will never notice the difference.

Velocity depends on the area under the pressure time curve (FT=MV). The primer will affect the peak pressure without increasing the average very much. No primer has ever blown a gun up. Also the firing pin strike can show several thousand psi, no gun has blown from that either.
Any change in case diminsion, primer seat, cartridge base ect. shows that you are pushing the brass into yield. That is the point start to thoink about what you are doing.
Good luck!

quote:

Originally posted by bounty hunter:
i have worked up a load for my kimber 7/08 that according to the books is over max., but the cases are not showing excess pressure signs.the primers are flat-flat but no primer pocket expansion etc. my question is calculation of pressure. is there a web site or program that can calculate approximatley how much pressure that i am producing?

B H

But, to paraphrase Bon Hagel, "All rifles are individuals, and what may be maximum in one may be quite mild in another, and vice-versa".

For example, I will not settle for 7X57mm Mauser performance from my 26" barreled 7mm Rem. Mag., despite the fact that many reloading manuals these days list such wimpy loads as maximum!

However, I don't go by case and primer appearance to determine what is a max. load. Rather, I go by case life - my max. loads must allow me to get ten shots out of a batch of cases before I have to chuck them out.

quote:

Originally posted by woods:
Nothing like saddling up your horse named "Agenda", applying the spurs and hoping the Indians show up show you can shoot at 'em, huh, HC

Hey Woods, Just thought bounty hunter ought to be able to see the "other side" of the discussion too.

Especially since it is the correct side.

I had some time last evening and found an article that might interest you in your search for the answers.

http://www.angelfire.com/ma3/max357/houston.html

Take a few minutes and have a look. You might find it very useful.

Good Luck.

Hey Woods, Have you come up with a Pressure Detection Method using those Stoney-Point things you like so well?

quote:

Originally posted by Hot Core:
Hey Woods, Have you come up with a Pressure Detection Method using those Stoney-Point things you like so well?

Nope, and it looks like the StrainGauge Tribe of Indians is not going to show up either.

Although I enjoy your shooting matches with them and do not know whose side I'm on yet.

But, you're right, I am definitely an Indian from Stoney Point.

quote:

Originally posted by bounty hunter:
that is the reason that i am shooting this load, because it is soooo acurate. the velocity is right where it should be for this powder charge. i have looked on several other reloading websights and have observed similar loads (even 2grns more than mine) published, but still all are above the books.again if i had major pressure signs i wouldn't even consider this load, this is just a curiosity thing for me to know what the pressure actually is

B H

Sometimes we create too much worry to satisfy our coriosity. You have a great caliber for deer and I have been happy with my 7mm08 for about 24 yrs now. You did not post your load but I can go 3 gr over max before any pressure sign shows up but I get the best accuracy at 1gr over.
I swiched to 140 TSX's this year and they do a great job on deer.
Good luck and draw some blood.

wll it seems i'm right on target cause i am exactly 3grns over max. and am shooting 120grn. TSX. killed two deer this weekend (does) neither moved out of their tracks.

B H

Hey Bounty Hunter, Congratulations on the kills.

Any chance I could talk you into providing us with a few more "Details" about the Hunt.

Stuff like the terrain, weather, time of day for the Kills, distance, Entry and Exit points and how did they look on the inside.

"Doc" that posts on here is a huge fan of the TSX Bullets as well.

Congratulations again.

quote:

i have worked up a load for my kimber 7/08 that according to the books is over max., but the cases are not showing excess pressure signs.the primers are flat-flat but no primer pocket expansion etc. my question is calculation of pressure. is there a web site or program that can calculate approximatley how much pressure that i am producing?

B H

With 7mm-08, 61,000 psi is the SAAMI law, and I don't care if your brass and your rifle like it, you must be arrested. If your rifle were a converted 270, you would be grandfathered-in.
A SAAMI agent, will soon be at your door.

Dutch, can you drive from Idaho to Texas tonight, make an arrest, and seize his load notes?

quote:

Originally posted by El Deguello:


For example, I will not settle for 7X57mm Mauser performance from my 26" barreled 7mm Rem. Mag., despite the fact that many reloading manuals these days list such wimpy loads as maximum!

Rats, another one!
Dutch, you will need to go to New York too.
Just put on your SAAMI expense account.
And thanks for keeping American safe!

quote:

an article John Barsness had written concerning a 25% rise in Pressure just by swapping from a CCI Primer to a Winchester WLRM.

I find this extremely difficult to believe.....25%???????

H C

i replied to your PM and gave some of the particulars, but i wish i could say that they were 400yds and a leapin' and a jumpin'but the truth is a good BB gun could have taken em' in a heartbeat. this was just a good weekend to do some management which we have to do a lot of.

TNECC please don't send the gustapo to texas i'll plead ignorance(naturally of course)and tell them also that the load came from the load section of this website.(truth) i'll hire woods to defend me since he is such a good orator(from another site)and i promise you that you will not have a chance in the fair court of public opinion.

B H

LMAO

I'll take the job bounty hunter and immediately file a writ of haveus a corpsus (2 of them dead deer)

we'll hire hot core for backup throw in 3 coyotes to your haveus corpus. YEAH i feel real comfortable here. probably an out of court settelment coming don't you think.

B H

Yeah, HC will have to substitute for a while, cause I'm leaving town tomorrow afternoon to hunt the Nov 16 - 20th Elk season in Colorado.

300 win mag with 180 gr TSX's

and

30-06 with 200 gr Accubonds

see y'all on the 21st!!!

i'm jealous.
have you killed anything w/the TSX's yet? you gonna love em' i think.
the two does were shot right under the ear and the exit hole was just bigger than a nickle but under a quarter. one of the coyotes was 240 long steps and the exit wound was exactly the same.have a great trip and give us a report when you get back.
come to think of it i'm gonna be gone for a while also. going to the lease this wed. afternoon and not coming home until the sun. or mon after thanksgiving. hopefully this texas weather will turn cool so that we don't have to hunt in shorts.

B H

quote:

Originally posted by bounty hunter:
...i replied to your PM and gave some of the particulars, ...

Hey BH, You will find this difficult to believe, but I must have deleted that PM by accident. I'd gone in to clean up some older ones and must have clicked on it by mistake.

The older I get, the more this kind of foolishness seems to happen. PITIFUL!!!
---

Oh yes, I do enjoy Blasting Coyotes. And the 7mm-08 does do a fine job on them. Good Off-Season reason to be afield.
---

Hey Woods, If you happen to see this before you leave, are you planning on carrying a rifle in each hand?

No, I got it, concerned that the Stoney-Point Fiasco created ammo which will jam the rifles. I understand.

Good hunting and all clean 1-shot kills to you.