Many posters talk about "excessive pressure." What really is excessive pressure? As long as the shooter is using a modern, first-rate bolt-action rifle, which will withstand ~150,000 psi, the case becomes the limiting factor in cartridge performance.

I've found that cases may fail - i.e., blown primer pocket - at just over ~70,000 psi. Primer pockets get loose quickly when you're loading ~65,000 psi. (i.e., as predicted by the NECO internal ballistic program).

Cases are cheap, and I may fire only one shot at an elk at 500 yds. If I bag the elk, the spent case - now with a loose primer pocket - can be discarded with minimal loss, especially given the overall cost of the hunt.

My concern, when loading HOT, is that the case may get stuck in the chamber - then I watch as the trophy of a lifetime walks over the hill. But, I haven't had that trouble, although I carry a 3-piece cleaning rod with me at all time to push a stuck case back out, if it ever happens.

What do you mean by excessive pressure? It is vaguely defined and seems to mean different things to different reloaders. What does it mean to you?

quote:

What do you mean by excessive pressure?

For most, I suppose it means pressure beyond SAAMI specs per cartridge.

SAAMI seems to be inconsistent. For example, given equivalent guns, the 30-06 (max. rating = 60,000 psi) and 270 or 300 RUM (max. rating = 65,000 psi) should have the same maximum pressure rating. There is nothing inherently weaker about 30-06 - indeed, the very case 270 is based on. I assume SAAMI did this, because there are many substandard guns around chambered in 30-06; so SAAMI plays it on the safe side. (Moreover, the 300 RUM, being a larger diameter case creates more stress on the action at 65,000 psi than either the 270 or 30-06 loaded to 65,000 psi).

I believe my definition above is a more practical definition. But, I would only recommend it to reloaders who weigh every powder charge, who carefully keep everything else equal, and who use only first-rate, modern bolt-action rifles.

Catastrophic failure isn't usually the issue in a bolt action rifle. It's wear and tear, which is a very non-linear function of peak pressure. Above a certain operating point, operating costs escalate rapidly.

More muzzle speed is not necessarily better. Surprisingly, there are many bullets that will give better penetration at 2500 fps than at 3000 fps.

What "operating costs" increase?

quote:

I believe my definition above is a more practical definition.

No one likes loaded questions.
If you already had your mind made up and just wanted to express your opinion, why didn't you just post your 2nd post first?

With the way that I shoot, a big game rifle may have 500 - 1,000 rounds at paper for every shot at game. I practice with full power loads that I can hunt with so if I need less power, I use a different cartridge.
I think that the long term wear would make me feel uncomfortable after a few thousand rounds of ammo at 75K psi. Considering that 75K may be an average and there could be a large amount of loads pushing 85K psi.

i just bought the RSI pressure trace...

should be here this week...

flattened primers mean excessive pressure....
but that's a "it's too far" already

jeffe

Fjold, how did you come up with the 75K and 85K figures? A ballistician at SPEER told me that at 80K the primer pocket is "toast" - ie., essential a black hole from a blown primer.

The operating costs that increase are case replacement and rifle operating life.

Things fail faster when stressed more, and the useful life falls exponentially as stress per event increases linearly.

You can also work yourself into a situation where you are spending all that extra money, and getting less penetration. Many bullets penetrate better at more moderate speeds.

Ackley's experiments show that primer pockets tend to fail on a single shot when peak pressures are about 75 KPSI IIRC.

I would consider excessive pressure is that which will cause the rifle to fatique failure. That point will be different between actions of the same design due to variences in tollerances and the occasional flaw that didn't show during proof testing.

I'm curious where you found out that modern bolt actions can "withstand" 150 kpsi. I'd be pretty confident that a 416 Rigby dia case loaded to 150 kpsi would destroy every modern sporting bolt action on the market. I'm not so sure that a .223 loaded to that level would produce the same effect.

All I can say is a little bit of knowledge can be a dangerous thing. Just because hot loads haven't yet ruined a gun, or injured you, doesn't make them safe.

If you really want a poweful round, then forget about the silly ackley improved rounds, and chamber for a much larger case. A 300-378 Weatherby at industry standard pressures will be signifigantly faster than a 30-06 ackley running primer popping pressures.

Speed is not a big benefits of AI. You do get a little gain, but not a lot... 100 fps max, and often just 50.

Paul is right. If you want a more powerful gun, get a bigger one.

Two very insightful tools are a chronograph, and the strain gage system that jeffeosso is getting.

I had some loads I'd used for years that went well over 70000 psi, never a blown primer.Get the pressure trace and know where you're at.

I've read Ackley's books. He states that pockets failed at ~65,000.

quote:

Originally posted by Paul H:
All I can say is a little bit of knowledge can be a dangerous thing. Just because hot loads haven't yet ruined a gun, or injured you, doesn't make them safe...

Hey AIU, The above quote by Paul is essentially what I was thinking when I read your initial post and second response.

You have stated some opinions that indicate an overall lack of understanding about how the actual Firing Process affects the firearm. Nothing at all wrong with that "if" you choose to learn from the folks trying to help you.

One of the basic fundamentals you are missing is a thing called Cumulative Metal Fatigue. When structures of any type are subjected to repeated pounding by high energy, eventually things begin to yield - even bolt lugs. In the case of a firearm, when the yield occurrs, it typically does not happen in a slow controlled sequence, but quickly with little to no warning.

People who think exactly like you are not uncommon. I've seen a good many of them on the Boards over the years and most are smart enough to eventually understand the error of their thoughts. But, it is the primary reason I refuse to buy a "Used firearm" from an unknown source today. I'm just not interested in purchasing a firearm that has been subjected to what you are putting yours through.

If you ever happen to take an Engineering Course called "Strength of Materials", a lot of the concern expressed by some of us will make a good bit of sense to you.

Rather than argue with you, I'll simply say you are mistaken about the overall effect of what you are doing and I'll wish you the best of luck.

Whatever Alf tells me it is!

ASS_CLOWN

Paul H, I got the 150,000 psi from an article in Guns Magazine - "The Rifles of Dakota Arms: Rifles to Dream of From the High Plains," (Feb '02 issue) by Dave Anderson.

[www.findarticles.com/p/articles/mi_m0BQY/is_2_48/ai_81477150]

Nice discussion of modern bolt-action rifles.

I'd be interested in everyone's comments, after they read the above article. Because brass is so soft relative to modern hardened steel, it seems unlikely that working within the limits of a brass case would cause serious stress to a modern bolt-action rifle. Yet, I would worry about blown primers and gas leaks that could cause harm to your eyes, especially with a poorly vented rifle. Finally, has anyone here personally witnessed a modern bolt-action rifle blowing up from "metal fatique" - that is, everything else being in control (i.e., no barrel obstructions, no wrong powder substitution, no double powder charges, etc.)?

/

Alf,

<long answer>
That you my friend are the little voice of reason in the back of my head! The one I try hard to ignore, because reason ain't fun (but then again
neither is recooperating in the hospital).

<short answer>
Nothing really, just have some fun. If someone needs to ask this type of question Alf, they are more than likely a lost cause anyway.

ASS_CLOWN

For once, Hot Core and I are in complete agreement.

Also, Ackley's pressure measuring setup was a copper crusher. As was common at that time, he reported his results as PSI. Today, we call those same units of measure CUP. True PSI are something else.

Excessive pressure is more pressure than you want.

When the primer falls out, that is too much pressure for me. If the primer falls out, the piece of brass is no good anymore. I want longer brass life in rifles. In pistols, I don't want a spent primer jamming the gun, but I only shoot brass once.

I reduce the load until the extractor groove stops growing, and then in rifles, I reduce it a little more for good measure, ala Veron Speer 1956.

for me, excessive pressure means the pressure at which if I continue to run my loads at, the hunt is over. I dont really care what the numbers are but if I get pressure that makes my rifle inoperable for whatever reason, thats excessive!

quote:

Originally posted by jeffeosso:
i just bought the RSI pressure trace...

should be here this week...

flattened primers MAY mean excessive pressure....
jeffe

jeffe,

Your new strain gauge with use may make you agree with my correction of your quote......

The flatest, most cratered, and ugliest primers I ever saw were shot in an old Model 94 .30-30. Factory loads, handloads looked the same. Excess headspace was causing the anvil-flat primer, wear in the firing pin to breechbolt area causing excessive clearence and the massive cratering and the primers were backed out .020"-.030" from the case! (another mis-quoted high pressure sign that isn't one.)

And all this was going on at an astronomical 35,000 psi!!

BigRx

quote:

Originally posted by Ackley Improved User:
I've read Ackley's books. He states that pockets failed at ~65,000.

If anyone should know it would be P.O. Ackley! His book has the record of more pressure excessive published loads than any publication I have ever read. One needs to be careful with his data!


BigRx

From my experience of occasional blown primers in chronographed loads, the NECO internal ballistics program indicates that blown primers occur at somewhere between 75,000 and 80,000 psi CIP piezo. I advocate keeping velocities at or below those velocities predicted by the NECO program set at 65,000 psi CIP piezo or below for any given caliber, bullet, powder type/amt. combination.

quote:

I've read Ackley's books. He states that pockets failed at ~65,000

65000 what, CUP, PSI, ???

There are LOTS of cartridges factory spec'ed to 65000PSI max, and they are not blowing primers, or even showing abnormally short case life. Maybe brass was softer back then...???

I don't know for sure, just my worthless opinion, but I think "Ackley Improved Abuser" is probably more like it.

quote:

Originally posted by Ackley Improved User:
I've read Ackley's books. He states that pockets failed at ~65,000.

And that means what?......The best advice I'd give to anyone is to not take too much of Ackley's writings as something of value.

It is truley amazing how thinking has done like dung, that is roll down hill over the years. Everyone thinks you need a 30/338 or 458 loaded to max to shoot an elk with. You cann bs some but not those that grew up in Western Colorado in the 1960s. My Uncle used a .270 with a 130 grain bullet to take Mule deer, Elk. antilope and even Moose in Montana. The key was shot placement. I have two good friends who still hunt to this day with a 30/06 thier dad used in 1960. They get several elk a year. And one's wife uses a .243 100 grain to take her yearly Elk. But all were taught years ago to place thier shots. My dad killed elk with his 30/30 with a 170 grain Remington corelok between the eyes and in the neck. But the mentality has moved from placing shots or "aim small miss small" to sling out a big piece of lead with 12 inch flames from the barrel. Oh by the way I forgot last year they got a big 6 point (12 point in the south) elk with a .260 Remington 140 grain at 400 yards. Right threw the neck and down he went.

The CIP system of measuring pressure is quite different from what we use here in the US. That is the European system, where pressure is measured at the mouth of the cartridge. Our US ANSI/SAAMI measurements are taken in the middle of the case. The two systems do produce different results. CIP publishes both CUP and PSI/MPa pressure data.

CIP stands for Permanent International Commission.

Denton, how different are the results between PSI Ansi/Saami and CIP piezo? Could you give us an idea - for example, what whould 65,000 PSI Ansi/Saami translate into CIP piezo?

To a decent approximation, ANSI/SAAMI PSI = -17230 + 1.27 x CIP PSI. The correlation is pretty good, with an R^2 of .88. It's not quite as good as the conversion from SAAMI CUP to SAAMI PSI.

The large negative constant suggests that this relationship only looks linear over a short range, and that the graph is actually curving upward.

Loading to pressures that wear out your cases before you have gotten at least 10 reloads out of them before you have to scrap them is excessive pressure, by my standards. Maybe not DANGEOUS, but excessive!

quote:

Originally posted by Ackley Improved User:
<SNIPPED TEXT>

Cases are cheap, and I may fire only one shot at an elk at 500 yds. If I bag the elk, the spent case - now with a loose primer pocket - can be discarded with minimal loss, especially given the overall cost of the hunt.

My concern, when loading HOT, is that the case may get stuck in the chamber - then I watch as the trophy of a lifetime walks over the hill. But, I haven't had that trouble, although I carry a 3-piece cleaning rod with me at all time to push a stuck case back out, if it ever happens.

I need a little more info here.

What gun, cartridge, bullet, and load data are you using here? Velocity too if you have a chronograph.

Also, when you tell me that, what are your average group sizes at 500 yards?

That is a more relevant number than velocity.

quote:

Loading to pressures that wear out your cases before you have gotten at least 10 reloads out of them before you have to scrap them is excessive pressure, by my standards. Maybe not DANGEOUS, but excessive!

This is probably the important criterion that is most quickly visible. All else is just predicting where this point will be, before it happens.

Denton, thanks for the equation and info. Using your equation indicates that 65,000 Ansi/Saami psi = 65,320 CIP psi - correct? - essentially no practical difference at ~65,000.

To repeat my previous comments, my experience (using my chronographed load data and the NECO internal ballistics program) indicates that primers will blow with one shot at 75,000 to 80,000 psi CIP - a value likely close to that for Ansi/Saami psi. When one begins to shoot at ~65,000 and over, primer pockets begin to loosen-up quickly - indeed, when you hit ~75,000 psi the pocket may loosen to blackened "toast" with one shot. This data fits with PO Ackley's data of 65,000 "psi" (likely CUP data, which tends to run 10,000 less than Piezo psi - that is, 75,000 psi as well). It also fits with what a Speer Bullets engineer has told me from their observations in a ballistic lab.

Even at this pressure level (i.e., 65-75,000 CIP psi) I find it hard to believe that a modern first-rate bolt-action rifle in good condition is even minimally stressed, because they are designed to operate at 150,000 psi and greater - twice as much.

Again the limiting performance factor for current ammunition is the BRASS CASE, and that relatively soft-brass case is going to show serious pressure signs before you get anywhere close to stressing the chrome-moly steel of the action.

Leaking gases and stuck cases are the significant consequences of hot loads. When loading at around 65,000 psi CIP, I haven't had these problems.

Mark, my current favorite long-range, big game loads are:

300 WM - 26" barrel, custom-made Rem M700
83 grs. Reloader 25 with 180 gr. Nosler BT
Oehler chronographed (3 screen) = ~3300 fps.
Note: An awesome, maximum! load - multiple one shot kills on elk at up to 415 yds. Alliant powder lists maximum for R25 in 180 gr. bullets in 300 WM at 82.3 grs. Sub MOA accuracy at 100 and 300 yds. Never shot at 500 yds.

30-06 Ack Imp - 26" barrel, custom Rem M700
66 grs. of Reloader 19 with 165 gr. Nosler BT.
Oehler chronographed (3 screen) = 3200 fps.
Note: Maximum load! Backup gun for the above. Sub MOA accuracy at 100 and 300 yds. Never shot at 500 yds.

Denton and Mark, I hope the above answer your questions. Any additinal comments?

Regards, Ackley Improved User

AIU,

quote:

30-06 Ack Imp - 26" barrel, custom Rem M700
66 grs. of Reloader 19 with 165 gr. Nosler BT.
Oehler chronographed (3 screen) = 3200 fps.

Do you have any idea what the pressure is on that load? I do. By the way, I have had 3 or 4 regular old unimproved 30-06s do that too, big deal. I even had a 7.62X51 Nato do almost that in a FAL (of course that poor little bastard suffered about 0.009" case head expansion as I recall, and not I wasn't using Rel 19).

Your 300 Winnie is a tad hot also, like in the neighborhood where you think primers blow.

You have much to learn young grasshopper. Much indeed.

ASS_CLOWN

AC, I get multiple reloadings from the cases from both loads. What is your explanation of that? AIU

I found this interesing quote on this forum from "Stonecreek." "Before going any higher [powder charge], try loading and shooting a single case 3, 4, or 5 times in succession with your hottest load. If you shoot a case five times and you don't have a loosened primer pocket or measurable head expansion, you're well within acceptable pressures by definition. The brass case is much weaker than the steel action, so as long as your brass remains intact, it's irrelavant what the absolute PSI is." What do you think of "Stonecreek's" comment?