308 Small Primer Brass - Ignition problem - Solution Found

[dcali]

Thank you. I observed a match last year where shooters on a very cold morning were having problems with their ammo shooting poorly in cold weather but then fine again in the warmer afternoon. It’s been speculated the federal primers don’t perform well with swings in temp and I will test it by freezing rounds. Of course there is every chance their loads went out of tune due to the colder weather. One shooter using a faster propellant and large primers had no issue all day. All shooting 155 class bullets in 308.

That’s the reason that’s commonly given for large primers in a .308, so it’s possible. I personally haven’t had problems in normal temperatures.

 

[Straightshooter1]

I recently bought some Lapua and Peterson Palma cases and have been testing and fire forming them after measuring everything I could think of. This is my first experience with .308 Palma cases, so I'm trying to get know them. I weighed the cases and took volume measurements before and after firing. Some unexpected data showed up in comparing my Lapua and Peterson Palma cases.

Average case weight for Lapua was 173.1 gr compared to Peterson's at 176.3 gr. The unfired Lapua brass (full lenth sized) average volume was 54.7 gr H2O and Peterson's was 54.1 gr H2O. After firing, the volume for Lapua was 56.0 gr of H2O and Peterson's was 55.4 gr of H2O. With Peterson's case weight being greater than Lapua's, I would have expected Peterson's volume to be greater given that the Peterson brass has significantly thinner walls (Peterson = .1300 - .0150 in thickness and Lapua = .0140 - .0154 in thickness). Apparently, the Peterson brass has a thicker head/web to have less volume and more weight with thinner walls.

 

[Brians356]

I recently bought some Lapua and Peterson Palma cases and have been testing and fire forming them after measuring everything I could think of. This is my first experience with .308 Palma cases, so I'm trying to get know them. I weighed the cases and took volume measurements before and after firing. Some unexpected data showed up in comparing my Lapua and Peterson Palma cases.

Average case weight for Lapua was 173.1 gr compared to Peterson's at 176.3 gr. The unfired Lapua brass (full lenth sized) average volume was 54.7 gr H2O and Peterson's was 54.1 gr H2O. After firing, the volume for Lapua was 56.0 gr of H2O and Peterson's was 55.4 gr of H2O. With Peterson's case weight being greater than Lapua's, I would have expected Peterson's volume to be greater given that the Peterson brass has significantly thinner walls (Peterson = .1300 - .0150 in thickness and Lapua = .0140 - .0154 in thickness). Apparently, the Peterson brass has a thicker head/web to have less volume and more weight with thinner walls.

You're measuring wall thickness only near the case mouth. It's not too unlikely the Peterson's body walls are thicker than the Lapua's, i.e. the Peterson walls tapers more toward the neck.
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[1shot]

Anyone know the spring lbs to use in a Kelbley Panda F-class or Atlas tactical action.?

I was told by Jim Kelbly to buy regular OEM springs for replacement as that is what they use. I got mine from Brownells and they work fine. The weight of them I do not know.
I hope this helps,

Lloyd

 

[Sandstorm]

Thank you Lloyd..much obliged.

 

[Keith Glasscock]

Went out today and shot a practice session with the LabRadar. I shot a total of 66 shots, the radar missed 2, and I didn't retain my cold-bore shot.

The temperature started at 51 degrees and warmed up to 58 degrees over the 3 hours of testing. The average velocity climbed from 2843 to 2846 over that temp swing and fouling buildup.

The 63 shots recorded had an ES of 18 and a standard deviation of 4.38 fps
with an average velocity of 2844.5 fps.

The load remained the same, 45.1 grains of Varget with the Lapua 167 scenar bullet except, I substituted CCI 450 primers for the Wolf SRM.

@Scott Harris called it. Thank you for the help!

 

[L W P]

Aaahhh, just in time for an issue I too am having with my first use of .308 Lapua Palma cases. I thought I'd try some and see how they worked out in my RPR with a 24" Krieger barrel mounted.

As I kinda anticipated, I found some cratering as I feel I'm going to need to bush the firing pin to avoid this. I accidentally bough some CCI 400's when I meant to get 450's. So I went back to the store and picked up some 450's and loaded up some of both to test using 44.0 gr. of 4064 behind 168 SMK's. Primer's were seated with a .003 crush.

So Saturday I fired 10 rounds of each and both primers performed pretty well. The cartridges with the 400's gave me a SD of 6.4, and ES of 18 and on a somewhat windy day I managed a .510 group. The 450's gave me an SD of 7.3, an ES of 25 with a .585 MOA group. Given that the cases are new with no case prep other that some lube for seating, the results surprised me.




The odd thing though was that I expected the magnum primers to produce more velocity that the other and it turned out the other way around. The average velocity for the 450's was 2684 fps and the 400's was 2717 fps. I'm going to run another test just like it and see if I get the same results. Shouldn't the magnum primer's produce higher velocities?

One other question . . .

I bought an RCBS small primer uniformer and I found that it was difficult to get it into the pocket, so I didn't force it and decided to take a bunch of measurements. The uniformer bit is .173" in diameter and the Lapua cases have pockets that are .172 in diameter. The number I've read as a "minimum" for small primer pockets is .173, so the uniformer is good for that, BUT . . . I'm wondering if I can find a tool that would better fit the Lapua primer pockets or would enlarging the pocket by .001 be of any concern (as in making sure the pockets stay tight over time)?


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I sent both of my RPR bolts into AD Arms to have the bolt face bushed and firing pins taken down to .062". That solved all of my primer issues using SRP brass in different calibers. You may want to check into AD Arms. And Andrew's work,prices,and turnaround times are great.