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  #21  
Old 09-14-2012, 02:59 AM
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Originally Posted by rifter View Post
I concur completely. I was only replying to the other poster who said NOT to call.
Can you imagine how the conversation would go when the question of CCI400 or 450 primers cam into it? If they keep it to part dimensions and don't mention primer issues, there should be no issue with calling.
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  #22  
Old 09-14-2012, 05:50 AM
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Rifter,

Yes! You were! Sorry about that. I'd meant to address Dmsbandit's point and my aging eyes skipped to your post heading for some reason. Dmsbandit clearly concurs with us that keeping the primers out of the conversation is the way to go. I wonder if the OP were to pick up a little Winchester white box or Federal .223 (except, not their mil-spec M885) if he wouldn't then have some commercial ammo primer appearance to complain about?


MZ5,

You are right about the Wolf, but he'd also said he had to use a magnifying glass to see any sign of cratering on the 450's, so it sounded to me like it's within a normal range and not as thin as the 400's. I don't know if he applied the glass to the Wolf or not.

This thread about a report on primers mentions that Wolf magnum LR primers seem to have thicker cups than their standard primer, and I'm wondering if maybe they use that primer in the ammo he shot?
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  #23  
Old 09-14-2012, 09:16 AM
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Interesting report from the M14 site, Nick, thanks! Particularly interesing that the CCI 200s were not flattening, but the thicker/harder #34s were.
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  #24  
Old 09-14-2012, 11:55 AM
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This old test showed CCI #200's near the bottom on gas pressure. It may be they just don't back out as hard as some others.
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  #25  
Old 09-14-2012, 05:46 PM
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Great stuff, had very little time to mess with it the past few days but have done a little more experimenting. Here is what if have tried.
lowest starting charge of H335 I found was Hodgden with a 77gr bullet, it was 21grn. We know it cratered with the cci 400, so how low do you have to go? Answer 19.5grn no crater with the cci 400 primer. 1.5 to 2 grns below min depending on what book you use.
Decided to try Varget, lowest starting I found was Hodgden at 21grns, so tried that and it cratered the same as 21 grns of H335, left it at that.
Checked neck tension it is .003
Fired a 65 grn sierra spt bt, with 18.5 grns of IMR 4198, and cci 400 primers (use this in another gun for plinking) no cratering.

Do you think it could be the bullet weight, lighter bullet no problem, heaver one crater below min charge.

I know just go with the lighter bullet and be done, but why would this happen??
And stay with cci 450 primers.
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  #26  
Old 09-15-2012, 03:14 AM
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Quote:
Originally Posted by TXasphalt View Post
Great stuff, had very little time to mess with it the past few days but have done a little more experimenting. Here is what if have tried.
lowest starting charge of H335 I found was Hodgden with a 77gr bullet, it was 21grn. We know it cratered with the cci 400, so how low do you have to go? Answer 19.5grn no crater with the cci 400 primer. 1.5 to 2 grns below min depending on what book you use.
Decided to try Varget, lowest starting I found was Hodgden at 21grns, so tried that and it cratered the same as 21 grns of H335, left it at that.
Checked neck tension it is .003
Fired a 65 grn sierra spt bt, with 18.5 grns of IMR 4198, and cci 400 primers (use this in another gun for plinking) no cratering.

Do you think it could be the bullet weight, lighter bullet no problem, heaver one crater below min charge.

I know just go with the lighter bullet and be done, but why would this happen??
And stay with cci 450 primers.
There's something here I can't quite put my finger on, but it has to do with slower powders at less than full charge. I burned up a lot of H-335 under 60 gr. bullets back when I was loading for a Mini-14, and had no problems with cratering. The #41 primer wasn't available then, but the 450 was.

Most of the powders that work well in the 5.56 also work well in the 6.8 SPC, and the cases are roughly the same capacity. I would try some AA-2200, which has proved to be one of the very best for the 6.8. Stick with the #41 primer in any case.
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  #27  
Old 09-15-2012, 11:09 AM
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I'll theorize that the heavier bullet and slower powder are letting the peak pressure dwell enough longer to start pushing the firing pin deeper while it and the hammer are still bouncing off the strike. That's letting a little crater fill-in occur. If there's anything to my wild theory, the cratered primer indentations should not be quite as far below flush with the head surface as the 4198 primer indentations are.
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  #28  
Old 09-15-2012, 11:26 AM
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Unclenick, may be on the right path. The cratered primer with the slower powder indentations do not appear as deep as the 4198 primers
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  #29  
Old 09-15-2012, 03:43 PM
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The magnum primer will light it up faster, which may be helping as much as the thicker cup.
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  #30  
Old 08-29-2013, 08:11 PM
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had some cci srm primers blow by today with the same load that had wsr primers that did not blow by. cooper21 223 26in 1/8barrel with 69sierrahp. go figure
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  #31  
Old 08-29-2013, 09:24 PM
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I use CCI #41 primers for my AR ( and Mini-14) loads. I loaded some 77 gr. SMK's in my Syrac upper ( with Wilde chamber). H335 would have been my first choice but I couldn't locate any, so I used some H4895 that I had on hand. I mike case heads as I'm working up a load and compare it to a factory load, in this case the factory load was some British NATO SS109. R.O.R.G. ( Royal Ordnance Radway Green).I was getting close to the expansion of my NATO load right away with my starting load of 22.6 grs. I shot up to 22.3 grs., carefully watching the expansion and the expansion didn't increase, but at .377, the loads seemed to be a bit too hot. Velocity at 22.6 averaged 2630, at 22.3 grs. velocity was 2690 f.p.s. But the primers on all weren't cratered. As others have said, cratering can be because of the firing pin tip shape, play around the firing pin hole in the bolt face or other reasons. I would not rely on primer cratering as a means of determining pressure. Without having the ultra expensive pressure testing equipment that the factories have, best way to determine when you've reached max is to mike case head expansion of your loads against a factory round ( or better yet several different factory loads) and use in conjunction with a chronograph. A Chrony works fine and is about a hundred dollar bill. I backed down the load to 22.4 grs. and was getting a little less case head expansion ,(.376) at just under 2600 f.p.s. This load shot 3/4" at 100 yards in my AR, and to my surprise, 1" in my 1-9' twist Mini-14.
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  #32  
Old 08-30-2013, 01:41 PM
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You can buy a Pressure Trace for around $500. I have one, and it works fine.

Case head expansion only tells you for sure that the particular piece of brass you have doesn't like the particular load you fired in it. It's a highly irregular indicator. Denton Bramwell, using the same lot of 7.6254R brass with the same load history, got CHE of 0.00001" from two cases at about 48,000 psi. one at about 49,000 psi, one at about 57,000 psi, and another at about 63,000 psi. At half that, 0.00005", the pressure that caused the expansion ranged from 32,000 psi to 57,000 psi. It's not too surprising when you consider that copper crushers can disagree by 25% firing the same reference load, and they're using calibrated copper slugs, the most accurate form of metal deformation measurement of pressure. The brass isn't calibrated and therefore is subject to much higher variation than the copper crusher.

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  #33  
Old 08-30-2013, 03:19 PM
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Lacking the $500 Pressure Trace instrument, I would think that measuring the case head expansion is better than just guessing what your loads are at by looking at the primer condition. I totally agree with you, flattened primers are a sign of high pressures, while cratered primers aren't necessarily so. I am also amazed at the number of people who reload and don't own even a cheap chronograph.
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  #34  
Old 08-30-2013, 06:21 PM
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Sandog,

Follow my link to Bramwell's article before you make your mind up completely. It makes reading individual case head expansions look little better than reading tea leaves because of all the scatter. However, the correlation isn't zero, so an average expansion of multiple rounds fired with the same load and lot of brass will get you a pretty good correlation to what that particular brass will stand. Again, the brass isn't calibrated. That's partly because SAAMI specs only control the exterior dimensions, and its partly because the hardness varies between makers. Hardness depends not only on the alloy, but also on the amount of work-hardening a case got in the forming process. Federal commercial brass, for example, is famous for being soft and primer pockets getting loose at load levels where other brands do fine. There's an article on different brass alloys used in commercial brass, here.

Also, there's more sensitive approach than measuring exterior case head diamether. Board member F. Guffey sent me a copy of a tool he'd apparently designed some time ago that measures flash hole diameters. That's where expansion is greatest and it presents the earliest clue that the brass is loosening up. So if you measure that and take an average for your load development cases, then remeasure and re-average after every load cycle, you'll get good notice when pressure's starting to bother the cases.

Flattened primers, like case expansion, is something that tells you that you are approaching the limit of the particular primer you are using, but doesn't clue you in to actual psi. In small rifle primers there's a lot more cup thickness difference between brands and types than in large rifle primers, so it's not uncommon for a load to flatten a standard small rifle primer but not the magnum primer from the same company. Also, just changing primer brands will often do that even if you stay with standard or magnum because the thickness and hardness aren't quite the same.

The main thing is, if you want to watch metal move, think "averaging" and don't read single examples as necessarily being proof of anything.


Kuzu,

Did you move the loaded rounds differently after assembly? One of the authors of the Precision Shooting Reloading Guide mentioned having a load that worked great if he loaded it at home, but caused sticky bolt lift when he loaded it at the range using the same tools. He finally figured out that in transporting the rounds to the range, the vibration from travel was packing the powder down enough to slow its ignition rate, reducing pressure.
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  #35  
Old 08-30-2013, 08:59 PM
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UncleNick, could you please explain what your post says about the vibration settling the powder and causing "LOWER pressure"? What I have experienced is that vibrated rounds, depending on whether the manufacture uses graphite as a retardant, tend to lose the retardant coating and cause the cartridge to "increase" pressures, rather than "decrease" pressures.

Prior to the Internet and back in my adolescent days, I experienced this issue (higher pressure) with loaded .270 Win ammo that I put in the tumbler for a couple of hours. I later learned that the tumbling effect destroyed the graphite retardant coating on the powder granules, thus causing elevated pressure readings.

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  #36  
Old 08-31-2013, 03:55 AM
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Unclenick, I'm sure there are better means of determining when you are approaching peak pressures than measuring case head expansion but I don't know if they are practical for everyone. I am not in a position, at least at present, to invest in a $500 tool, and while the flash hole method sounds good, I would not want to drive home form the range while shooting a string of loads I'm working up to deprime each case, or even to take my press to the range, or invest in a hand decapper to pop out primers while I'm testing loads. There are many variables in reloading, and we should strive to eliminate as many as possible for consistencies sake. Despite hardness variances in individual brass, I would think that using the same make and lot of brass for my loads ( Brit Radway Green) as the factory load I am using for a test standard is all I can do under the circumstances. So I will continue to "read the tea leaves" like I've done for the last 35 years.
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  #37  
Old 08-31-2013, 03:58 AM
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Could the OP please photograph some cratered primers with good close up shots?

I think there is something else going on here. I will try and explain.

Basically if you do not have enough striker energy that gives enough energy to the primer to sustain the pressure curve long enough for the pressures to subside will result in a situation where the rising pressures over power the striker energy , pushing it back into the bolt face followed by the primer.

In law enforcement there is a saying "If it looks like a duck, walks like a duck, quacks like a duck, you have a duck. I can assure all if you have a rifle that "looks like a AR, feels like a AR, sounds like a AR you are most likely the owner of something that is not what you think you have.

I have a friend who was a procurement contract officer with the Army and he bought the spare parts for M16 family and he told me "95% of the AR parts out there won't meet the drawings (real M16 drawings, not reverse engineered) for the M16. Anyone want to guess what happens to the parts made for the gov't that are rejected by the gov't???????

The original M16 has a copper indent requirement of .022". The industry used to have a copper indent requirement of .020" indent but now they have backed off to .016" indent recommendation as there is no controlling authority that forces them to produce to ANY indent requirement.

I have had new out of the box rifles give a indent of .015" ! ! ! ! ! I wrote the Chief Engineer of the firm and advised him there is a QA problem in his line. I got a call from the head of product service wherein they wanted a conference call with the three of us. I came to find out they had not checked firing pin energy in "last 15 years".

A couple years later I went to NRA Show in Charlotte and went to that vendors booth and asked if there was anyone there from engineering and this guy jumps up and says, "I'm from engineering." I asked him what the indent requirements were on their rifles and HE DID NOT HAVE A CLUE AS TO WHAT I WAS TALKING ABOUT.

I have the holders and the coppers to check firing pin energy on 5.56, 7.62 and 30.06 and do so regularly.

I got a new Remington 7615 a number of years back and besides having in internal bore so crooked it could not be sighted in at 100 yards! ! ! ! I sent it back and also told them they it had insufficiant striker energy. Got rifle back with new barrel and they either did not change striker spring or the one they changed did not have enough energy either.

I got hold of Wolf Springs and bought a bag of hammer springs and changed it out. They had much more energy than the factory springs and the "cratering" disappeared immediately and hasn't returned.
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  #38  
Old 08-31-2013, 04:53 AM
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Lacking the $500 Pressure Trace instrument, I would think that measuring the case head expansion is better than just guessing what your loads are at by looking at the primer condition. I totally agree with you, flattened primers are a sign of high pressures, while cratered primers aren't necessarily so. I am also amazed at the number of people who reload and don't own even a cheap chronograph.
Using primer flattening as a pressure indicator isn't very good either in many cases. If you have a condition of excess headspace, that allows the primer to back out on ignition to take up that extra space. Pressure building up will reseat the primer, and can make it appear as if pressure was too high. That varies depending on the type of primer used, how fast pressure ramps up, etc.

If all cases are properly sized with minimum headspace, then primer flattening can have some validity, since it isn't the reseating that is causing it. Even then, however, it is at best an imprecise method of checking pressure. A chronograph will tell you far more about what's going on inside that case than anything else short of a pressure trace rig.
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  #39  
Old 08-31-2013, 08:36 AM
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I have seen what appeared to be severely flattened primers in a standard pressure .38 special load. The culprit was simply a primer that was too powerful for the application.

There is a reason for primer flattening, but it isn't always high pressure.
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  #40  
Old 08-31-2013, 11:58 AM
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Sandog,

We don't seem to be on the same page, somehow, and we're dragging the thread off the topic of pierced primers. I only suggested the Pressure Trace because you'd said expensive professional pressure equipment was the only alternative to case head expansion. I merely corrected that statement by pointing out you can now buy amateur pressure test equipment that does a good job for about the cost of an Oehler 35P chronograph or a mid-range Dillon progressive loading press. Those are a fraction of the cost of a professional conformal Piezo transducer rig. It may still be more than many folks are interested in spending, which is fine, but each thread gets a lot more readers than participants, so I wanted to let that be known.

Absent pressure measuring gear, it's worth reading the list of signs in the sticky on pressure signs at the top of this forum. I started that thread because no single pressure sign turns out to be great or as repeatable as pressure readings. But watching for all of them, pierced primers included, and stopping to reason out the cause of any sign that appears before increasing charges further will greatly improve your odds of not running the gun warmer than is best for it. I would not recommend relying on CHE or any other single pressure sign by itself, but you get to choose what you want to do. Read Bramwell's article and decide for yourself if the degree of reliance you put on CHE is justified or not.


Allen Foraker,

The vibration you and I are talking about are, in one sense, two different animals. In Dan Hackett's case it occurred in transportation (vehicular vibration) where the ammo would have been in boxes and kept from pointing in different directions. That fixed orientation allows settling of the powder. If you have it in a tumbler, the orientation is constantly changing and breaking up any settling that tries to occur.

I have to say I am surprised by the results you got tumbling finished rounds. Read this article on the effects of 205 hours to 300 hours of vibratory tumbling on different powders being nil. Powders have to handle sometimes enormous amounts of vibration exposure in transport without performance deteriorating. Imagine the vibration ammo was exposed to in propeller-driven aircraft in WWII. Perhaps you had an unusual lot, or else some other variable got involved.


TXasphalt,

Humpy's experience is interesting. If the bolt and firing pin protrusion all seem to be in line in your gun, a new hammer spring is cheap and easy to try out.
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Last edited by unclenick; 09-01-2013 at 05:37 AM. Reason: typo fix
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