Flattened primers

[NoOne]

I'm wondering if my flattened primers are a problem, or if I should ignore them.

Barrel is a 19.5" Alexander Arms, brass is Lapua, primers are CCI-450, bullet is 123 grain Nosler custom competition, powder charge is 30.2 grains of W/748. (max is listed as 30.5) Velocity is around 2550 fps depending on temperature outside. Brass ejects nicely to about 4 o'clock relative to the rifle.

What bothers me is that my primers all look really flattened. If this was happening with a bolt gun, I would suspect over pressure. However, my velocity indicates I'm not loading too hot.

I anneal the brass, and many cases have 8-12 loadings on them. If primers are loose when I seat them, if necks crack, or if any primers pop out during shooting, that brass is discarded.

Out of my most recent range session of 75 rounds fired, one primer popped out, and 4 cases had cracked necks, so I realize my cases are getting toward the end of their life cycle. However, many of the cases still have really tight primer pockets, so I presume they are still OK to use.

Are my flattened primers anything to be concerned with?

[terrywick4]

flattened primers are an indication of over-pressure. Is this last batch shot at a warmer temp then when you worked your load up? Pressure increases on a load with warmer weather and if you were not seeing this before I would be concerned.

[LRRPF52]

We often see primer flattening on gas guns because gas guns need some slop in the headspace to chamber reliably.

I also see it with many factory bolt guns that have excessive headspace, even with charges that are nowhere near max pressures.

What I look at first is the chronograph, and am I seeing erratic Extreme Spread, as well as cratering, harsh recoil, things like that. Are you jammed into the lands? What's your COL with that load?

[sneaky one]

Do you have any combined over all length measuring tools? Anything?

Yes, flattened primers are a huge warning sign! Hope you don't have a short throat chambered bbl. You have the same setup as I do.

Did you just take up reloading? If so, this may be an easy fix.

[bwaites]

Flattened primers in gas guns MAY be an issue, but several factory loads have shown flattened primers in guns I know have proper chambers. There are dangerous reasons for flat primers and some of no consequence. LRRPF52 gives good advice above.

[Bwild97]

I have 3 boxes of fired factory Hornady 123 A max that would scare the pants off any who put faith in believing that primers are a reliable tell tail indicator of high pressure. All 3 boxes were fired from a recent 18" rlgs, build to check function and accuracy. As soon as I am able I'll post up some pics of the case heads and fired primers.

Long story-short, don't put too much faith in the appearance of fired primers, LRRPF52 offers sound advice, use all aspects of the shot, and ask yourself if that was "normal" when compared to factory loaded ammo.

[LRRPF52]

[dmsims21]

I would look at the COL. 123 NCCs need to be seated short in my rifle. Max is about 2.25 (SAMMI chamber). The bullet length varies a lot with those bullets, so you need to measure several. With five bullets, my max ranged 0.025.

[rushmc1a]

What book is this in?

[NoOne]

I am not new to reloading, have been doing it since the 1970's, and am able to produce very consistent, accurate ammo. I go by what the manuals say to do, and work up to charges that I use. I stopped at 30.2 grains because I got the best accuracy there, and max is 30.5 in any case. The manual has the listed max velocity for the bullet I'm using as around 2650 fps, but i presume that is out of a 24" barrel, and my shorter barrel will give less velocity. My velocity is 2550 fps in hot weather, and about 2480 fps if it is really cold out. I'm using Winchester 748 powder, so I realize ball powder is more temperature sensitive than other available powders.

C.O.A.L. is 2.260 inches for the bullets I'm using, and the manual says that for that bullet, I should be at 2.260 inches. I measure headspace after firing the rounds, and push the shoulder back about .002 thousandths. Bullets aren't jammed into the lands, and I don't notice any ejector swipes on the brass.

The primer pockets on my Lapua cases (the only ones I'm using) seem to last a very long time, so based on my low velocity, and longevity of the primer pockets, I suspect something other than over pressure. Cases are measured for overall length prior to loading, and trimmed when appropriate, so the cause isn't over length cases. Cases extract easily, and as noted in my first posting, cases eject to about 4 O'clock relative to the rifle.

I have checked the velocity I get from my chrono against velocity I obtained with a friend's magneto and they are pretty close, so my chrono isn't giving me bad readings.

I get the same results with both the Nosler CC bullets and with the Hornady AMAX bullets. Maybe both bullets need to be seated to a shorter COAL?

Maybe I'll have to seat these bullets to an even shorter COAL, which means reducing powder charge and working up again, because I would be burning powder in a case with less overall volume relative to the powder charge size.

Edited to add: I do have tools to measure COAL, headspace to a datum line, and depth to where the bullets engage the rifling. All these measurements seem to check out, but there could always be an anomaly.

[bwaites]

NoOne,

Your answer is in your own knowledge. The load is safe, and what you are seeing is an anomaly often seen in gas guns, even with completely safe loads. I suspect if you went to a slightly heavier buffer, a Tubbs carrier weight system, a heavier spring, or something else to slow opening of the bolt just a few ten thousandths of a second, your primers would return to normal. As noted above, I see this from time to time with factory loads in my Grendels, and even in 5.56 loads.

Just for kicks, because the Nosler tends to have a bit of a round meplat in comparison to some of the bullets we load in the Grendel, try moving it back to 2.200 and see if the primers are flattened. I'll bet there isn't much difference.

Your explanation of your reloading history and knowledge answers all my questions!

Welcome to the board!

[Bwild97]

From my 18" Saber brl. chambered by Precision Firearms. I also had a Tubb CWS w/ tungsten insert installed at the time I fired these rounds.

[NoOne]

I have extra buffers and buffer weights around...how much extra weight to the buffer do you think would help out? The rifle has a full length stock/buffer system, not a carbine stock with it's shorter buffer.

I had suspected something with the gas system, and the explanation about the timing/opening of the action fits right in with that.

MANY THANKS!

[Bwild97]

I'm not convinced that the CWS is doing enough, I like that it slows the bolt cycling down, but I am thinking I will have to install an adjustable gas block to effectively change (delay) the bolt unlock timing.

[NoOne]

Reducing gas flow to the system would most certainly slow down system operation. If I could simply add some additional weight to the current buffer and get a reasonable fix, that would sure be cheaper (and therefore more preferable).