quote:

Originally posted by Ackley Improved User:
I believe some posters here are over reacting - operating at 65,000 is not dangerous in modern bolt-action rifles.

It is dangerous when such a pressure level is achieved in brass never meant to be loaded that high.

In addition, there is no way to accurately conclude that you are operating at 65000 PSI, or 75000 PSI. Your ballistics software is guessing. You are guessing. We are all guessing. And we are all guessing the average pressure. Remember that not every round fires the same chamber pressure. Some are high and some are low. If your average is at the threshold, then some of your shots will exceed that threshold. Hence, it is wise to err on the safe side.

Please read this portion of the posted article.

Escaping gases from a blown primer or cracked case from a hot load will NOT destroy the action - a well designed bolt action will vent the gases away from the shooter. It works as Dave Anderson says!

Guns blow up when something else is very wrong - that is, chamber/barrel obstruction, wrong bullet, double charge of fast-burning powder, wrong cartridge, faulty construction, etc. Alf posted pictures of an OBSTRUCTED GUN.

I've blown primers and I didn't know it until I looked at the case. I've had fatigued brass split at the base of the case, and I didn't know until I looked at the case.

I doubt that many posting here will change their minds regarding any of this. But, guns are like flying and investments - some people can take risks, others keep they money in the bed mattress and never get on airplane. It's your choice.

quote:

"Rifle enthusiasts like to argue about which action is the strongest: In fact, all current commercial actions have a huge margin of strength. Bolt-actions are typically strong enough to handle pressures of 150,000 psi or more.

The brass cartridge case, however, will take pressures in the 80,000 psi range. Since commercial ammunition is usually loaded to maximum pressures of 55,000 to 65,000 psi, there is an ample margin of strength -- but the cartridge case will fail long before the action does.

Why not use a stronger material such as steel for the cases? Because brass has an excellent combination of strength, pliability and elasticity. When the gun is fired, the pliability lets the case expand to tightly grip the chamber walls, which seals off the powder gases from coming back into the action. When the bullet exits and pressure drops, the elasticity of the case lets it spring back to near original dimensions, allowing the case to be extracted. Although strong, steel cases wouldn't seal off the chamber as well as brass, wouldn't extract as easily, and would be subject to rust.

When comparing actions, it's not a question of strength. As stated before, steel is much stronger than the brass cartridge case. The question is, in the event of a case failure, how well does the action protect the shooter from the escaping gases? Occasionally we hear accounts of how someone had a rifle "blow up" but miraculously wasn't injured. Actually the rifle didn't blow up (if it did, the shooter likely wouldn't be around to talk about it). What really happened? The case failed and the action controlled and vented the escaping gases away from the shooter, just as its designers intended.

A hundred years ago when technology was less advanced, case failures from poor brass were more of a concern. Today's manufactured cases are of such uniformly high quality that such failures are virtually unheard of. Now when a case fails, it is almost always a result of shooter error: firing the rifle with the bore obstructed, loading the wrong caliber cartridge, or poor handloads with excessive headspace or the wrong powder."

Of course, you do not need anyone on this board's permission to load your rifles to any pressure you like. There is no little man inside the cartridge that automatically blows up your rifle when you exceed some secret number of PSI. It's your rifle, and your body parts. Do with them as you please.

However, there is at least one huge hole in your theory. Suppose that the average modern firearm will stand 150 KPSI. Now, are we to assume that all modern firearms will do this? Or that there is some variation? Obviously, there is some variation.

I probably have as much data to base an estimate of 20 KPSI as the standard deviation, as the author you quote has basis for his estimate of 150 KPSI, which is to say, not much.

So some arms will stand 210 KPSI, and some will fail as early as 90 KPSI, according to that. The real number depends on the cumulative stress on the firearm, and its original construction and materials.

Your average cartridge may generate 70 KPSI, but not all of them do. As pressure goes up, powder burns faster. So you add more powder, and pressure goes up, but so also does variability. Look at the Alliant max load for a 30-06, with 180 grain bullet, and RL22. It's about 46 KPSI, IIRC. There is plenty of room left in the case for more powder. Why didn't they go up? Probably because the load becomes too highly variable.

You have variation in rifle strengths, variation in cartridge pressures, and if cartridge pressure reaches rifle failure pressure, you'll know about it right away. Much more likely, though, you'll just see excessive wear on your gun.

So, if you like those outcomes, go for it. I think it is exposing yourself to a little risk, and added expense, in order to achieve a flatter trajectory and, at best, breakeven in penetration, perhaps a net loss. But that's my opinion, and I live with its consequences, as you live with yours. I truly hope we never find out that you were wrong.

I would submit that doing what I'm doing carefully with first-rate modern reloading components and bolt-action rifles is far safer than the reloads from a careless or naive reloader, who is more likely to make one or more of the following mistakes:

1) Using fast-burning powders (i.e., IMR4350 or faster) with the resultant risk of a double charge.

2) Substituting the wrong powder - that is, a faster for slower-burning powder.

3) Substituting a heavier bullet for a lighter-bullet load (or carelessly changing bullet type without load development).

4) Causing and/or not looking for barrel/chamber obstruction - for example, forgetting to remove the cleaning brush (or like items) from the barrel after cleaning the gun.

5) Putting the wrong caliber cartridge in the gun.

6) Reloading with the wrong bullet diameter.

7) Failure to monitor pressure signs, which have always been there when I've looked for them.

8) Using substandard guns and reloading equipment.

9) Failing to chronograph loads during load development - checking for excessive velocity.

10) Failing to plan loads in concert with NECO internal ballistic calculator or other reasonable information sources - at least have some idea of the pressures you're working at.

Denton, to live life is to take risks - I risk life and/or limb everytime I drive into work. Given the current state of affairs on American highways, that's a major risk. Last year ~45,000 Americans lost there lives in car accidents - think of all those who were injured. If you knew where I lived and the highways I drove to work on, you'd believe me, when I told I'm taking more risk going to work each day than from blowing myself up with 66 grs. of R19 in a 3006 AI behind a 165 NBT with a Rem700 - a load I shoot 15 times per year.

If you let yourself become obese, you're putting yourself at risk - in fact a recent study suggested that currently life expectancy in the USA has dropped 2-5 years because of obesity. Indeed, life itself can be viewed as a terminal disease with a median survial of ~75 yrs.

There are many ways to blow-up a gun, even for those loading within SAAMI specifications.

Being a reloader and case developer, excess pressures are when the cases don't last for 10
to 30 reloads or longer.And there is enough of the right powders out there to get hairy
energies out of big bores; with decent peak pressures, that don't destroy brass in 2 shots.Ed.

Ed, cases are cheap - why must they last for at least 10 reloadings? - especially when compared to the overall expense of an elk-hunting trip. Yet, some cases are somewhat expensive, such as those used by benchrest rifle shooters. But, some benchrest rifle shooters routinely run at 70K+ pressures - use the case once or twice and throw it away. I'm a benchrest rifle shooter - maybe that'w why I'm not afraid of routine 65K pressures.

Loads that allow you to push the primer in with your finger after after 3 shots is about where I would put excess pressure. A slight pressure spike or softer than normal case and it will be loose on the first shot and with perhaps a bit of sticky extraction. By excess pressure I mean would reduce such a load but I would be happy with 5 shots.

Mike

Benchrest chambers are different, you know. They do not let the case expand very much. The case is therefore more likely to stay together.

Have you ever had a close encounter with hot gas being blown through a small hole close to your face? I once blew a gasblock off my AR-15. The handduard contained most of the gas, but I do not want to experience that again.

quote:

I'm not afraid of routine 65K pressures

Routine 65k is not the problem...you indicated that you are running routine 75-80kpsi...that is what these guys are trying to tell you.

If you are only getting 1-2 reloads before primer pocket failure, you are well over 65k!

I like the race car analogy I read here once...you can run the engine at top end for a short while, or at a moderate speed for a long while. Can you afford to replace engines often, and handle the liability when they fail?

CDH, I'm not running at 75K to 80K - that's a pressure where primer pockets get toasted with one shot. I'm 3 grains of R19 below that point with the 165 gr. NBT in 30-06 AI, and 2 grains below that point with the 300 WM.

I try to run an average of 65K, but knowing I'll range up to 70K. Like Mike, I like to get at least 3 reloadings per case - actually 4 if you count the fire-forming shot, which is at low pressure.

Ralf, a benchrest rifle gunsmith makes all my guns. Although they're not tight-necked guns, I'm certain the chambers are as tight as any benchrest rifle chamber - he's really, really good. When I've crossed the threshold to a blown primer, the gases are vented - I feel nothing until I inspect the case, because the gases are vented away. Sometimes the spring-loaded Sako extracter is dislodged by the leaky primer pocket, but I put it back on the bolt face at the range with my fingers - it works fine. Yes, the leaking gases from a blown primer won't even destroy the after-market Sako extracter. This happens rarely, since I've learned to recognize the signs, when I'm getting too hot and it's time to STOP!

Ackley Improved User

I said I regard a life of 3 shots as excess pressure and a load that let me seat the primer with my finger after 3 shots I would reduce. 5 shots is my cut off point.

Mike

AIU, I'm pretty firm in my viewpoint that what you do is your business. And I agree that if you are a careful and experienced reloader, you are much less likely to make a mistake that could get you hurt.

So, here I go, meddling again.... sorry.

I'm also a very careful reloader. I do six sigma for a living, and those good habits spill over into my hobbies. I never have more than one type of powder on my bench, nor more than one kind of bullet. I have rules about which hand charges the case, and how the case and bullet go into the press.

I've fired thousands of rounds, and have never worn out a case, or suffered a head separation, except once.

Once, and only once, I popped a primer. I have no idea why. Obviously, I made a mistake of some kind. Maybe you won't, but I did, and probably will again someday, regardless of how careful I am.

As you would expect, the rifle serenely digested the cartridge, and I was unaware of the problem until I ejected the casing and the primer fell out.

So, all was well, because I had ample safety margin.

Denton, clearly, what we all do regarding reloading is our own business - this forum cannot physically reach to our reloading benches. It can only reach the bench through the influence of its content. I'm here exchanging ideas, picking-up new points, and sharing experience. Actually, I'm impressed with the knowledge level of many of the posters; and, I appreciate all your input, including ACs.

What you describe in your last post is what I've experienced - a first-rate, well constructed bolt-action rifle can digest a blown primer without much ill effect. But, I don't like making a habit of it; in fact, I avoid it, since little is to be gained pushing past the limits of the brass. I've outlined my technique of maximizing performance, while staying away from blown primers or stuck cases - basically, it's go with the slowest burning powder that will fill the case and bring the pressure to the desired level. In fact, I'm going to check out Retumbo in my 25-06 AI, 280 AI, and 300 WM. Also, I'm moving toward R25 in my 30-06 AI with 180 gr. NBTs.

I have seen video footage of a DSArms in .308 loaded to the brim with bullseye just to see what happened, of course all done in a lab with not one person in the room, remotely "detonated". Not the same as a bolt rifle, but it still is another example of receiver failure from excess pressure even though steel is harder and more resilient than brass. Hey ALF, where did you get those pics of the 270 Weatherby, I would like to read the article.

AI,

Benchrest chambers are tight at the casehead as well. They are cut with a reamer made specifically for one brand of brass with maybe .001" total clearance. Unless you made a custom reamer for your gun, you are running .005" or more at the sase head.

Rifles are not made to survive blown primers on a regular basis. A blown primer and a blown casehead are far apart on the destruction scale.

You don't know what pressure you are running. You are assuming 65K, but you are probably running more, especially if your chamber is tight, as you implied.

This thread keeps going and going - like the Ever Ready bunny. Topic and discussion must be worthwhile.

AIU,
I see you are a fan of getting the max out of your gun. I am the same way.I've got a 280 AI that I guess I've tried every powder I know of. I'm now a big fan of N160. It is the most consistant powder I've found,if you haven't tried it you might want to.It's the best I've found.
Deano

Deano, thanks for the input - wanna share some load data. I got tons for the 280 AI.

Also, see the quote below. Maybe we should load BELOW SAAMI - this SAKO went up with factory ammo.

quote:

This was posted over at The High Road by Harry Tuttle
http://www.thehighroad.org/showthread.php?s=&threadid=103191 He got it from BPCR.net http://www.bpcr.net/content.htm originally posted by Rick A. Shay.
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This is not BPCR, but is definitely worth a look, folks. I have posted ten relatively high quality images of a brand new SAKO bolt action rifle in .300 Winchester Magnum caliber, with synthetic stock, and fluted barrel. On the 15th shot out of the box, it went KA-BOOM! The first 14 shots were from a box of Hornady factory ammunition. The fifteenth shot was from a new box of Federal factory ammunition.

The barrel is now in three totally separate, longitudinal pieces, the receiver is split down the middle, with left and right halves, and the forestock is a black plastic memory. The cartridge case is split from mouth to case head, and looks like a three-petaled flower.

With the limited number of images available - here are my thoughts on the event:

To my non-professional (since I don't get paid for my opinions,) eye this is a failure caused by included flaw(s) in the barrel steel. Once the barrel started to fail, the fractures continued forward, generally along the edge where the flutes join the major diameter of the barrel. Note, in the image of the cartridge case, there does not appear to be any significant swelling, or deformation, of the case head, itself, and I can not see any melted brass, or brass flow. I cannot see any brass flow in the shattered area of the split barrel, either. To my mind, that precludes the possibility that it was a high pressure round causing the failure. (Unfortunately, I do not yet have any images of the case head, itself, or of the bolt face, which might add additional credence to my point.)

The shooter was NOT seriously harmed because he was shooting from the bench, apparently wore proper protective gear, and had his arms cradled under the butt - in the rear sand bag area.

OK. enough teasing. Here's the link to the photos http://www.bpcr.net/site_photos/Sako-KA-BOOM/index.htm. - Rick A. Shay, Colorado

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Wow! I've never seen any gun KA-BOOM like this.
Joe

quote:

Originally posted by Ackley Improved
Also, see the quote below. Maybe we should load BELOW SAAMI - this SAKO went up with factory ammo.

Have you tried blending powders to achieve a perfect burning rate for your application?

Ralph, No - have you? My application for high-performance hunting is to use the slowest burning powder that will fill the case (usually a compressed load) and achieve the desired pressure of ~65K. Usually, this is R25, but sometimes R19 or R22.

Quite some time ago on this site a couple of people from Africa were posting up some loads they did with mixing powders.

I think in Africa their local powders are missing a burn rate like 4064. They were mixing a slower and faster powder and I think from memory they had it as a compressed load so that the powder mix remained as they had originally mixed it.

It all worked out OK for them. I seem to also remember that they varied the mix or more correctly the distribution of the powder throughout the mix and that gave similar results.

As far as I am aware if all goes off perfectly then in a normal load all the granules of powder are ignited at once and the burn rate is controlled by each granule as opposed to ignition spreading throughout the powder as is the case with an piston engine.

Mike

With so many powders to choose from - fast to slow - why mix?

/

Alf, please share your experience with us. What did you mix and what were the results?

quote:

Originally posted by Ackley Improved User:
Ralph, No - have you? My application for high-performance hunting is to use the slowest burning powder that will fill the case (usually a compressed load) and achieve the desired pressure of ~65K. Usually, this is R25, but sometimes R19 or R22.

That is my preference as well, however ifn you want to squeeze the last few FPS out of your gun, you should experiment with mixing powders.

For example, in my 22-250, N550 is too fast for 55 grain NBT's, but N560 is too slow. What I really need is a N555, but none is available.

In your application, R19 is probably too fast. You need a R20.

If you think you're running 65000 psi and cases are only lasting three loadings, I'd say send some of your ammo and get it tested. For years I shot some 7x57 loads that some of the people here shot for years as well that put 160 Noslers at over 2825 fps. The cases used in this load will last at least 10 loadings, no pressure signs at all, even hunting in the heat in Africa. When I set up a pressure trace system, every shot was over 70000 psi. I've since backed it down to just under 2780 fps, 64000 psi. I had an individual load that I on purpose left in a hot chamber for a while and it went 79000 psi, no extractor flow, no primer leakage, this was all in an old Ruger 77. I've had other guns that I know weren't loaded as hot that were starting to extract sticky. Another thing, I sure wouldn't try to get another 100 fps and pack around a cleaning rod to punch cases out in case of a stuck one, I don't need anything like that to ruin a hunt. I would of course keep a rod in camp, just common sense.

Ralf, IMR/Hodgdon strongly recommends not mixing powders - you've likely read their admonition. What have you mixed and what have been the results? Did you brew the powder you wanted? Did the mix show intermediate properties?

jstevens, you make some very good points. But, you're also putting much faith in your pressure trace system to measure pressure accurately. What pressure did the NECO ballistics program estimate for that 2800+ fps load and the adjusted sub 2800 fps round. The way those tracer systems "calibrate" has me bothered - much is assumed on faith. If they would offer internal standard rounds to calibrate with and periodic internal standard quality control rounds to check the system, I'd buy into it.

I look forward to both your answers. Regards, AIU

quote:

jstevens, you make some very good points. But, you're also putting much faith in your pressure trace system to measure pressure accurately. What pressure did the NECO ballistics program estimate for that 2800+ fps load and the adjusted sub 2800 fps round. The way those tracer systems "calibrate" has me bothered - much is assumed on faith. If they would offer internal standard rounds to calibrate with and periodic internal standard quality control rounds to check the system, I'd buy into it.

AIU, Why would you suspect the strain gage systems readings over the Quik Load program that, as I understand, claims a accuracy level of ~10% vs "a few hundred" psi for properly set up strain gage system??
Personally I`d feel better with a tool that told me what happened -within a few hundred psi-in my rifle with a given load then one that takes a "guess" at what psi it will produce in everyones rifle as being the true result I`ll get in mine.
I`m not saying quik load isn`t useful, it is. The fact so many use it allows it has to give pretty good information for most situations. I have to question it`s accuracy though over the strain system inre to acual results in a specific firearm.
This is just my opinion, everyones got one.........

I just got off the phone with an IMR/Hodgdon ballistics engineer. They workup their loads with a state-of-the-art Piezo transducer system - that is, they measure internal pressure directly and don't estimate internal pressure with assumptions regarding chamber metal stretching. This is what he had to say (parapharsed) about internal pressure and case failure:

"...given a d 30-06 case, primer pockets can fail in a brand new cases beginning at ~65,000 piezo psi - but not always. The incidence or probably of case failure varies according to brass quality and chamber tightness with high brass quality and tight chambers being more resistant to case failure...(He likes Lapua brass best and the 6mm PPC is quite resistant to case failure.)..Certain case designs are also more or less resistant to high pessures...Nonetheless, the probability of pocket failure will increase with rising pressure becoming essentially 90% plus at 80,000 psi piezo...Blown primers are not that bad (small amount of escaping gas), but case head separation (large amounts of escaping gas) can destroy a firearm with most such events occuring with over charges of fast burning powders at ~100,000 psi or more. But chamber/barrel obstruction of any cause will cause massive over pressures...Weak firearms are at greater risk - that is, old designs (esp. old military), lever actions, automatics, bad gunsmithing in a bolt actions, etc (the old relatively weak military 30-06 chamberings are why SAAMI rates 30-06 at 60,000 psi and the 270 at ~63,000 psi)...He concurred that using slow burning powders are safest when you're at case capacity...He felt nothing is wrong with compressed loads...IMR7828SSC will be packaged this week and available soon...He thought it was the best powder the "Canadians" made...Retumbo is a very good powder in large capacity over-bore cartridges with heavy bullets...He didn't recommend it in 300 WM until you get to the 200 grain bullets or larger, and then it'll be a compressed load...Retumbo at very low pressures is dirty and inefficient... IMR/Hodgdon maximum loads are set when they reach 97% of SAAMI maximums to allow for all the variables, which are many today."

That's as much as I can recall for now.

Ol'Joe, how well does your pressure tracer system correlate with the NECO Quick Load program?

A piezo system is not what you would call especially direct.

You infer pressure from the force of the piston, knowing the relationship between area, pressure, and force.

When you apply the force of the piston to the piezoelectric crystal, you cause an electric charge to appear on the surfaces of the crystal. You assume that this charge is directly proportional to applied force.

Then you further make use of the formula Q = CV, where Q is charge, C is capacitance, and V is voltage. You assume that C is fixed and constant, and that the voltage presented to the inputs of the amplifier is proportional to Q. And you assume that your amplifier has constant gain, and a fixed DC operating point, and that it is well designed to handle the high output impedance of a piezoelectric crystal.

You have a conversion of pressure to force, force to charge, charge to voltage, and voltage to a reading.

It's a fundamentally sound technique, because all those assumptions are valid in a well-designed system. But it is not an especially direct technique.

It also not incredibly accurate. I recently found a 12.5% pressure discrepancy between two commercial labs.

quote:

I recently found a 12.5% pressure discrepancy between two commercial labs.

Where is there a commercial lab that tests ammo?

Sorry... should have been more clear. I was referring to differences between books by Hodgdon, Speer, etc.

If you have a 1 grain difference in two 30-06 loads, the pressure error is a lot more than just the weight error in the amount of powder.

The curve of pressure vs. charge rises exponentially, so the first few grains don't add near as much pressure as the last few grains. The curve is sufficiently linear over a range of 10,000 PSI or so that you can treat it as linear.

A 1 grain difference in an '06 case is usually about 2,000 PSI, or about 3.5%, and a 1 grain difference in a 243 is about 3,000 PSI, or about 5%. (Of course, more or less, depending on powder, bullet, etc.) So I found two loads, with similar muzzle speeds, 2.5 grains apart, using the same powder and weight of bullet. So the pressure discrepancy is about 12.5%.

The same lab, on the same day, with the same tech and lot of ammo is doing good to repeat a 10-shot average to much better than 1,000 PSI.

So what do you think about Richard Lee's published estimates on reducing charges - in brief summary...

1% powder reduction = 1% velocity reduction = 2.5% pressure reduction? again, as a rule of thumb?

It ignores some basic physics.

Muzzle speed is not linear with charge weight. If you look at the chemical energy to kinetic energy conversion, muzzle speed should be linear with the square root of charge weight.

If you take your baseline as 100% charge, and increase to 105%, speed should go up with the square root of 1.05, and energy should x1.05.

Of course, it's more complicated than that since the higher the pressure, the faster the powder burns, the sooner the pressure curve peaks, and the smaller the volume the gas has to expand into.

quote:

So what do you think about Richard Lee's published estimates.......

The best useage for Lee's manual is to tear each pages into 4 equil sections, and use them to stock the outhouse. It rates somewhere between the Sears catalog and the phone book on both the tear strength and cleaning action scales. Other than that it's a fairly useless book.

quote:

thouse. It rates somewhere between the Sears catalog and the phone book on both the tear strength and cleaning action scales. Other than that it's a fairly useless book.

i won't say that i agree or disagree with you, but wonder why you state that?

quote:

Ol'Joe, how well does your pressure tracer system correlate with the NECO Quick Load program?

Denton, how would you answer the above question? Have you made comparisons betweent the two? The IMR/Hodgdon engineer didn't use the program, but a Speer ballistic enjineer said the NECO Quick Load program was impressive and quite accurate correlating powder charge, pressure, and velocity. Has anyone else compared the two?

Sorry, I don't have any real data on that issue. I've never tried the program.

I don't know of any reason that you can't build a very satisfactory model, but I think it would require some way of accounting for lot to lot variation in powder quickness, and chamber tightness. Maybe it does...

Denton, you seem like someone who would enjoy the program - you might consider getting a copy. I'd be interested in your side-by-side comparison with your pressure tracer system.

You're correct the program considers each powder according to properties specified by the manufacturers, yet they do provide variance assuming +/- 10% lot-to-lot variation - which, as you know, can be quite significant in reloading.

For example, I have 8# of R19 that seems to be acting more like Norma MRP than Aliance specified R19.