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  #21  
Old 08-29-2009, 06:25 AM
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No, I haven't messed about with that powder yet. What is the grain shape like? I would think a compressible spherical would be easy, but you wouldn't want to squash the holes that run through a stick powder much. Though, 10% or so probably wouldn't matter much. Perhaps that's part of the trick to compression making it work better?
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  #22  
Old 04-11-2010, 11:29 AM
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flame cutting

Flame cutting is a pressure sign that i noticed when i used a hot unique load in my K-frame .38 I didn't see it covered in your list.
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  #23  
Old 04-11-2010, 02:27 PM
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Thanks. I will add it in.
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  #24  
Old 08-01-2010, 09:35 AM
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Uncle Nick,
I don't know how you came across all this info; reading, reasoning, calculating, or experimenting.

Some of the of the pressure signs you write about, I have found via high pressure experiments.

I have a hard time imagining you doing destructive experiments.

How did you collect that list of pressure signs?
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  #25  
Old 08-01-2010, 10:43 AM
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I'm pretty sure I've found it all just by reading. I don't think I've ever discovered a new pressure sign all by myself, unless you count brass in the face from a double-charge in a 1911 about 17 years ago. I didn't put that one on the list, figuring that by the time you see pieces of anything it will be obvious you've gone too far. I have run one destructive test for someone else, but it's not a realm I normally experiment in, as destruction of my guns comes at my expense.
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Last edited by unclenick; 12-19-2010 at 08:22 AM.
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  #26  
Old 04-09-2011, 03:30 AM
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Thanks, good post and one that everyone that handloads need to review and understand.
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  #27  
Old 08-11-2011, 10:42 AM
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Quote:
Originally Posted by unclenick View Post
Case primer pockets getting loose in five reloads or fewer.
a) That is the real limit I have found in load work ups for 1889 7.65x53mm Mauser case head built with a large Boxer primer pocket will have this problem somewhere above 68kpsi in Quickload; In 22-250, 243, 6mm Rem, 250 Savage, 257 Roberts, 25-06, 260 Rem, 6.5x55 [US made brass], 270, 7mm-08, 7x57mm, 280, 300Sav, 308, 7.62x51mm, 30-06, 8x57mm, 338F, 358, and 35W.

b) That is the real limit I have found in load work ups for the 1950 designed .222 case head with small rifle primer built with a small Boxer primer pocket will have this problem somewhere above 80kpsi in Quickload; 17 Rem, 204 Ruger, 221 Rem Fireball, .222 Rem, .223 Rem, 5.56x45mm, .222 Rem mag, 6x45mm.

c) That is the real limit I have found in load work ups for 1925 Holland and Holland 300 H&H Magnum built with large Boxer primer will have this problem somewhere above 68kpsi in Quickload; 6.5mm RemMag, 7mm RemMag, 8mmRemMag, 264 WinMag, 300 H&H Mag, 300 WinMag, 338 WinMag, 350 RemMag, 375 H&H Mag, 458 WinMag

d) That is NOT the real limit I have found in load work ups for the 1889 Mauser 7.65x53mm case head design, when built with a small Boxer primer pocket; 22BR, 6mmBR, 6x47mm, 6.5x47mm, 7mmBR, 30BR, Lapua small primer 308. For those, the real limit pressure sign is a pieced primer.
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  #28  
Old 08-11-2011, 06:33 PM
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That's interesting feedback. Like all pressure signs that depend on brass, there is some irregularity in the stretch count, too. Softer heads, like Federal, can stretch in just one shot at normal pressure levels (some report Federal factory loads stretch the primer pocket so the brass is not reloadable in the usual way). I'm not surprised to hear some is tough enough not to move much at all. Pressure signs have to be watched for collectively. No way around it.
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  #29  
Old 08-11-2011, 09:50 PM
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Possibly a shorter statement of one of the indicators:

Look for an orderly progression of muzzle velocity vs. charge weight. If muzzle velocity stops going up, or if it goes up too much, you have a problem.

I categorically reject any statement that expansion of more than .0005" indicates too much pressure. The geometry of a 223 case is vastly different from that of a 338 Rem Mag case, and they will respond very differently to the same pressure. And, well, you already know my view of PRE and CHE anyway.
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  #30  
Old 08-12-2011, 05:54 AM
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Yes. You'll notice I never included that number in the list. The use of cartridge cases as a gauge material, as your PRE and CHE results show, is a little like using a copper crusher with random uncalibrated slugs of varying starting thickness.

Perusing SAAMI's 1992 centerfire rifle document, ANSI/SAAMI 2299.4-1992, you find on page 119 (PDF page 125) the example of the same lot of .30 Carbine reference loads measured by copper crushers at nine different facilities. You see the average result for individual equipment as high as 41,200 CUP and as low as 32,800 CUP, while the average velocity difference between the two facilities getting those extremes was just 0.5% (close to the average of the velocity SD between the two). I know these are just 10 round samples, but still, it's enough difference to suggest the crusher is just not a very reliable measuring system. And that was all done using calibrated copper slugs. Throw in uncalibrated slugs of varying size and composition, as case brass represents, and it's not surprising that 2:1 errors could not only occur but not be extraordinarily rare.

I'll use your suggested verbiage change. "If muzzle velocity stops going up…" logically includes velocity going down, as some have observed can happen, but I think I'll add that just to be explicit. I'll generalize the rest a little more and make a note in the change log at the bottom.

Thanks for the feedback.
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Last edited by unclenick; 08-12-2011 at 06:00 AM. Reason: typo fixes
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  #31  
Old 08-12-2011, 03:46 PM
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Strange happening at the range yesterday.

Took out the 20 rd box of 6.5x257 Robt's AI ammo that was handloaded 11/02/07. 10 rds on the same end of the box had rounded primers protruding from the pockets as if they were only partially seated. The other 10 rds on the other end of the box were perfectly normal with nicely below flush primers. All have the same propellent loading of 49.5 gr IMR4350 (off a digital scale measured to nearest 1/10 gr by hand), the same CCI BR2 primer and 129 gr Hornady Ballistic Tip bullet seated to same COAL. The load is slightly compressed and yields 2990 fps/avg. Not a firewall load in any sense.

This flabergasts me!
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  #32  
Old 08-12-2011, 06:54 PM
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Might pull one with a high primer just to be sure all looks normal. Odd thing to find. The pockets weren't loose, I suppose?
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  #33  
Old 08-12-2011, 08:48 PM
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Although this box of brass (nickle plated, I might add) is on it's 27th reload, the pockets are still tight. Would have to be to hold the primers while they bulged into rounded shapes like that. I'm thinking some sort of internal pressure. Compressed powder usually pushes the uncrimped bullets out further until relieved, but can't see how the powder could work into the flashhole to cause this.

Half way afraid to use the kenetic puller - will have to dig out the RCBS collet puller after figuring out how to get the high primers into the shell holder. Hey - ! just remembered the spring loaded holder jaws of the Co-Ax press are perfect for this! Will have to give it a try in the morning and report back.
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  #34  
Old 08-13-2011, 07:26 AM
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A slow pull sounds like a good idea. I didn't register that you meant the primers were that round. Now I'm more suspicious that the powder started breaking down and pressurized the case. Surprised it wouldn't slowly bleed out, though. Fired cases don't usually achieve a hermetical sealed at either end unless some corrosion started and accomplished that.

Another thought would be just the other way around. Bad primer pocket scratch leaks coupled with primer seal lacquer being cracked and letting water swell the primer pellet until it bulged the cup.

The last thought is to ask whether the bulged cases could have been nearer something warm than the others in the box. Heat will accelerate breakdown of any chemistry.
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  #35  
Old 08-13-2011, 09:48 AM
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No, Nick -

The box of ammo was placed on the "loaded ammo" shelf along with several thousand other types of loaded ammo. A spot check of the others prove no similar results.

The cartridges in the same box with normal appearing primers all shot beautifully with no outward excessive pressure signs or felt recoil. I'm pretty sure the powder for all loads were from the same container, but as much IMR4350 I use, there could have been a different container used. However, all of it is from the same lot as the stuff was all purchased out of the same shipping case in 1 lb cans. Haven't pulled any yet, so will verify powder condition when doing so.
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  #36  
Old 08-17-2011, 09:20 AM
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Thought I should report back on this curious incident.

Pulled the bullets and dumped the powder on all affected cartridges. Bullets were tight in the necks, so rolled them between steel plates to break the bond and then pulled easily. The powder passed the visual and smell test with no sign of deterioration or rusty dust. Primers fell out easily (they were over half way backed out anyway). Cases looked good, still within length parameters, so neck sized and reloaded with W-W LR primers and original powder/bullets.

At the range this morning (95 - 100 deg) all shot perfectly and grouped well. Complete mystery to me.
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  #37  
Old 08-17-2011, 09:32 AM
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Quote:
Originally Posted by dentonbramwell View Post
Possibly a shorter statement of one of the indicators:

Look for an orderly progression of muzzle velocity vs. charge weight. If muzzle velocity stops going up, or if it goes up too much, you have a problem.

I categorically reject any statement that expansion of more than .0005" indicates too much pressure. The geometry of a 223 case is vastly different from that of a 338 Rem Mag case, and they will respond very differently to the same pressure. And, well, you already know my view of PRE and CHE anyway.

I feel that for me, the handloader, in a strong rifle, the absolute pressure does not matter.
What matters is brass life or pierced primers in the lists I posted above.
If the absolute pressure COULD be known, it would probably introduce error in adjusting powder charge for what DOES matter.

For me and my reloading process control for my rifles, I have found I want ~ 4% reduction in powder charge from any expansion in the extractor groove. That expansion may be asymmetrical, so I must slowly spin the case to find it.


This is different from Vernon Speer's 1956 statement that one should back off 6% powder charge from any expansion when writing a reloading manual.
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  #38  
Old 08-17-2011, 02:16 PM
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Tnekkc,

You may be comfortable working that way and you might have a super beefy rifle. I don't know, but for the safety of newbies reading this thread, let me throw some concerns in about brass-based load work-up.

First, though, let me suggest there are reasons for trying to learn absolute pressure or something close to it. One is the same reason manufacturers want to know it, and that is to make one load portable between guns. Another is to know you are not prematurely fatiguing the steel in your gun, in which instance measuring what happens to the steel rather than the brass is rational (a strain gauge system is best for this purpose). A third is to avoid excessive throat erosion, which Scottish ballistician Geoffry Kolbe points out will begin increasing disproportionately with pressures above around 58,000 psi. One hates to shoot a barrel out as the first sign that a load was warmer than assumed.

If you have read Denton's article and looked at his data, you'll discover brass is amazingly inconsistent as an indicator. Despite his using the same brass lot with the same load history, a given degree of expansion in one case might occur at half the pressure at which it does in the next. A load determined by looking at expansion in either one would be way off what the other could handle, one way or the other. He'd have to average a substantial number of loads at each charge level to get confidence an expansion result could be applied to that whole brass lot as a generalization. Most of us have seen this brass inconsistency indirectly in the form of irregular case growth from one round to the next when we check to see if trimming is needed.

Wm. C. Davis, in the (now out of print) NRA book, Handloading, referred to case and primer and some other pressure signs as "subjective" pressure signs. By contrast, actual pressure instrument results are "objective" pressure signs, regardless of calibration problems. On page 132 of the 1986 printing, he writes:
"There are two important reasons that subjective pressure signs should not be used to justify extending loads upward beyond the maximum loads published in a reliable data source. First is the fact that cartridge cases may vary considerably in hardness and strength. . . though cases within the same lot are unlikely to vary as much as cases of different lots, the differences may nevertheless be quite appreciable. The second reason is that chamber pressures may vary considerably from shot to shot, even if the loading is carefully done. When powder charges are increased to the point where a few rounds show casehead expansion, and then reduced only slightly, the chances are that the small sample tested has not included the extreme combination of an unusually high chamber pressure in an unusually soft case. That combination will eventually be encountered, however, and the result might be an expanded head, a stuck case, and a disabled rifle, or even a serious gas leak."
So, though many folks work contrary to Mr. Davis' advice, for safety reasons I have to advise the average handloader against it. The one problematic aspect of his advice is how you determine that your source of load data is "reliable". That is why you keep watching for those subjective pressure signs, anyway. Despite their low level of reliability in isolation, when you get one you need to stop working up until you can be sure it was a fluke. When you get more than one simultaneously, you may be accordingly more confident you have an "issue". This is why I maintain the list in the OP.
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Last edited by unclenick; 08-17-2011 at 02:23 PM.
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  #39  
Old 08-19-2011, 10:51 AM
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Nick gave very good technical reasons why exceeding listed maximum safe loads isn't a good idea. Here are some philosophical ones for what they're worth.

Any device is subject to failure even when operated within design parameters, much more so when operated outside of them. When firearms fail the results are commonly catastrophic, not only to the gun, but to the shooter as well. They can even be fatal, and have been on occasion. There isn't a group so small that it is worth the risk trying to shoot it with loads out beyond the maxima recommended by the powder manufacturers, when the penalties for failure include serious injury or death. Any increment in performance on target similarly gained by overpressure loads will similarly be much too small to be worth the risk.

It is not wise to depend upon some margin of safety assumed to have been built into a firearm. That may be true in the design of a particular model, but there is always variation in quality between individual examples, and engineers have been known to make mistakes. Where is the gun you're shooting in that range of variation, and how do you know? The fact that it held together for the last round doesn't mean for an instant that it will for the next.

Getting away with bad judgement doesn't change it into good judgement. Staying within specs hugely reduces the chance of a tragic end to a day at the range. If not of yourself, at least think of those who may have to clean up the mess.

These are strong words, I know, but I'm with Uncle Nick: New shooters and handloaders should have a clear and unequivocal statement of the risks involved with excessive pressures.

Best,

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  #40  
Old 08-19-2011, 11:03 AM
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I agree that while some can climb Mt Everest, there are many who should only climb stairs with treads, risers, and rails that meet code.
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