One thing I keep seeing is that I am getting "flattened" primers on most of my .223 loads for my bolt action. Some, including a few factory loads, even have cratered primers.

What is odd is that non of the loads are withing 5% of the max load in the Hornady book, and a few where just pratice low power loads.

What is it that I am seeing? When I use the some of the same ammo on my AR, I don't see any cratered or flattened primers.

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Originally posted by NEJack:
One thing I keep seeing is that I am getting "flattened" primers on most of my .223 loads for my bolt action. Some, including a few factory loads, even have cratered primers.

What is odd is that non of the loads are withing 5% of the max load in the Hornady book, and a few where just pratice low power loads.

What is it that I am seeing? When I use the some of the same ammo on my AR, I don't see any cratered or flattened primers.

To paraphrase what Bob Hagel said in his book, GAME LOADS AND PRACTICAL BALLISTICS FOR THE AMERICAN HUNTER, "Every (gun) is an individual. What proves to be maximum in one may be quite mild in another one, and vice versa." This may be your problem here. However, please note that flattened primers can be due to other causes as well as excessive pressures. For example, a cratered primer can be caused by a firing pin that is a little small for the diameter of the hole, the shape of the firing pin tip, firing pin protrusion, etc. Soft/thin primer cups can cause this as well, and some brands are softer than others.

What are your velocities like? A chronograph will help you sort Pressure "signs" from the chaff.

Try neck sizing a few cases, and see if the primers look normal. Flattened primers are quite often a sign of undersized brass, not pressure. HTH, Dutch.

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To paraphrase what Bob Hagel said in his book, GAME LOADS AND PRACTICAL BALLISTICS FOR THE AMERICAN HUNTER, "Every (gun) is an individual. What proves to be maximum in one may be quite mild in another one, and vice versa." This may be your problem here. However, please note that flattened primers can be due to other causes as well as excessive pressures. For example, a cratered primer can be caused by a firing pin that is a little small for the diameter of the hole, the shape of the firing pin tip, firing pin protrusion, etc. Soft/thin primer cups can cause this as well, and some brands are softer than others.[/QUOTE]

Good advise to follow. Most reloading manuals also have a chapter or two dedicated to just what you're asking; how to read pressure signs. Find a book you like and buy it.
There is also the case expansion method espoused by Ken Waters and others. This works when coupled with a chronograph and factory ammunition for a control. Where it gets sticky however, is when one tries to extrapolate pressures for that little extra in underloaded factory calibres. This is about as good as it gets without computerized equipment(strain guage).
This has worked for me for 20 years, and will work for you if you keep in mind that everything is approximate. I have found that some of Ken's loads are conservative, and that is good company to keep when working with the unknown.

Don't have a chrono, but I just remembered something about the brass.

There were a few loading of .223 that I did before I trimed the cases (didn't have a trimer yet). After shooting some of those loads, I did notice that a significant amount of brass was trimmed off (for me anyway compared to my .308).

I also have been wondering about the firing pin. Since I see the same signs on factory ammo, I wonder if that could be a problem. How do I check it?

quote:

Originally posted by NEJack:
Don't have a chrono, but I just remembered something about the brass.
[QUOTE]

There were a few loading of .223 that I did before I trimed the cases (didn't have a trimer yet). After shooting some of those loads, I did notice that a significant amount of brass was trimmed off (for me anyway compared to my .308).

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I have no idea of how the 308/7.62 compares with the 223/5.56 other than both operate at high pressure, but what it does sound like is that the rounds in question were overpressured because the cases were too long. It's an easy fix with a case trimmer.

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I also have been wondering about the firing pin. Since I see the same signs on factory ammo, I wonder if that could be a problem. How do I check it?

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Before I did anything else I'd give the gun, specifically the chamber, a good cleaning. If it is a new rifle some fresh factory ammunition as a control measure will give you the answer you're looking for. If the factory ammunition suffers the same ill effects the other ammo did the problem is physical/mechanical and lies with the weapon, if it doesn't the problem is the ammo in question. However, if the weapon in question is used, I'd recommend you take it to a smith before doing any more shooting.
That's the best I can do with the information at hand. Good luck.

The rifle was brand new when I bought it, and has been a good shooter.

With factory ammo, the primer is almost always flattened the same as in reloaded ammo. The only time the primer cratered with factory ammo was with some military surplus a friend gave me (didn't shoot it anymore after that).

I have had a smith look at the gun, although for a different issue (scope mounting), and I asked him just to give it a once over.

This weekend, I will shoot some of the loads I am using in my RRA AR and compare it.

AR I understand, but what is a RRA? Also be aware that each rifle is an individual, and as such will exhibit different characteristics even when fired with identical ammo.
Glad to hear a smith has given it a clean bill of health. With that said, I'll tell you there is more to look at then just the primer.
The case head itself has many a story to tell. On the face (where the headstamp is) look for rub or burnish marks. If it looks just like a new one (except for the usual carbon/smudge marks) that's a good thing. Scrapes, shiny spots, and extractor marks are bad. Don't confuse extractor with ejector as they are different. On your AR the extractor is that little toggle clip on the side of the bolt. The ejector is that round spring-loaded thingy inside the bolt face. It looks somewhat like a push button. My point is that with excessive pressures, the case will pick up an imprint of the hole in the bolt where the ejector resides. This is not a good thing.
Another area to look at is just forward of the case head, or web. This is the area where the brass thins out as it is drawn into shape, and isn't solid like the head. Normally there is a visible ring left there after firing. That area is marked because it is not secured by the chamber like the forward areas of the case are. This is also the area where reloaders take measurements while experimenting with load development. This is also an area that thinns over time with repeated reloads. When you trim cases you are basically cutting off breaa that has been peened forward from this area. It is also an area that can fool the novice if dies are improperly adjusted, because that can lead to a case head separation.
Anyway, find a good reloading book, study the pictures and get familiar with cases.

RRA is Rock River Arms. I bought a nice 26" varmit barreled AR.

I have checked the case head for any oddities before. The one batch of odd mil surplus ammo that was hot did have some markes on the bases, but no ejector marks.

I know that both guns are unique (believe me they are as picky as can be be ), but what is odd to me is I expected the semi Auto AR to show pressure signs before the bolt gun.

It seems to be just the opposite. The AR functions well with 24.5 gr of AA2230 with a 55gr VMax, and the primer look just like the off the shelf Black Hills stuff. In my Savage, the primers are flattened until I get to around 24-23.5 grains of AA2230. Factory ammo, from cheap Fedral rounds to moly coated Winchesters, also gives flattened and cratered primers.

Not a big problem for what I use it for, I mainly use the AR for praire dogs now, but seems odd.


I don't load hot, so this has always been something that is puzzling to me. Before I started loading the .223 I loaded for my .308 Win for a couple of years, and never had any of trouble like this. Was just trying to see if there was something I was missing.