Thread: .308 flattening primers

Hey Team

I’ve been developing a load for my kimber .308 and have noticed that my primers are flattening out quite badly.

Im loading .5gr under max load and am seating at 2.80“ so it shouldn’t be a pressure issue.
Getting 5 shots under an inch at 100m 2730fps with a 150gr nosler BT.

I am thinking that it’s a headspace issue, how do i check it and how do I remedy the problem?

Advice is much appreciated

Cheers
Strider

Have you measured the shoulders on fired vs unfired brass? That'll confirm or rule out headspace.

That said... any other pressure signs? Would expect to see other problems if excessive headspace was an issue.

Have you measured to see what kind of jump the bullets have to the rifling?

What brass are you using? Need to drop the powder charge on some mil stuff.

When did you last give the chamber a good clean? Ideally no oil or residue in there, and no carbon buildup.

What primers are you using? CCI's are a bit harder than most. Federal are soft as shit and flatten out very easily.

How flat are we talking here? If you're up at/above 60kpsi, expect a LR primer to really start pancaking. Have they still got any hint of rounded edges? Have you noticed them getting flatter as you worked up or has it been consistent? How easy do they pop out when you de-prime? Are the pockets expanding? Still tight enough to hold a fresh primer?

... Pictures?

Using federal premium brass, federal primers. Unsure of jump. There’s heaps of jump, have used my oal gauge and the projectile I’m using is barely seated when at the lands but mag length dictates oal of 2.80 “ Clean chamber, no heavy bolt lift.

I don’t have any way to measure fired vs I fired brass

Assuming no ejector or extractor marks on the brass, then soft federal primers giving a false alarm is my bet.

Some pics to confirm would be great.

What and how much powder are you running? I’m having some issues in a 308 Forbes that runs the same bullet at the same pace. Post a picture of you primers. It might help.

Greetings Strider B,
Your velocity of 2,730 fps would indicate normal pressure assuming your barrel is not stupid short. Minimms2 suggested above that primer appearance is the least reliable indication of pressure. I would go further and suggest it is practically useless. In my experience flattened or even riveted primers is more an indication of head space. If you are full length sizing with the die hard down on the shell holder then head space is almost certainly the problem. To get over it, if it bothers you, you can either neck size or set the full length die a little above the shell holder so the case just chambers easily. This is a hit and miss affair and initial adjustment is best done with the depriming gear removed. In any case cartridge cases fired with slightly excessive head space need periodic checking for incipient head separation using a piece of sharpened bent wire feeling for a groove just above the head of the case on the inside of the case wall. Hope this helps.
Regards Grandpamac.

Originally Posted by grandpamac

Greetings Strider B,
Your velocity of 2,730 fps would indicate normal pressure assuming your barrel is not stupid short. Minimms2 suggested above that primer appearance is the least reliable indication of pressure. I would go further and suggest it is practically useless. In my experience flattened or even riveted primers is more an indication of head space. If you are full length sizing with the die hard down on the shell holder then head space is almost certainly the problem. To get over it, if it bothers you, you can either neck size or set the full length die a little above the shell holder so the case just chambers easily. This is a hit and miss affair and initial adjustment is best done with the depriming gear removed. In any case cartridge cases fired with slightly excessive head space need periodic checking for incipient head separation using a piece of sharpened bent wire feeling for a groove just above the head of the case on the inside of the case wall. Hope this helps.
Regards Grandpamac.

This ^^^

Sent from my S60 using Tapatalk

Originally Posted by grandpamac

Greetings Strider B,
Your velocity of 2,730 fps would indicate normal pressure assuming your barrel is not stupid short. Minimms2 suggested above that primer appearance is the least reliable indication of pressure. I would go further and suggest it is practically useless. In my experience flattened or even riveted primers is more an indication of head space. If you are full length sizing with the die hard down on the shell holder then head space is almost certainly the problem. To get over it, if it bothers you, you can either neck size or set the full length die a little above the shell holder so the case just chambers easily. This is a hit and miss affair and initial adjustment is best done with the depriming gear removed. In any case cartridge cases fired with slightly excessive head space need periodic checking for incipient head separation using a piece of sharpened bent wire feeling for a groove just above the head of the case on the inside of the case wall. Hope this helps.
Regards Grandpamac.

I have a neck sizing die for .308 so I might try a few loads with that, I found that last time I use it some of the rounds were a bit hard to chamber.

Originally Posted by kiwijames

What and how much powder are you running? I’m having some issues in a 308 Forbes that runs the same bullet at the same pace. Post a picture of you primers. It might help.

3 flat primers and one unfired for reference.

44.0 gr of 2206h under 150gr nosler BT

Originally Posted by veitnamcam

This ^^^

Sent from my S60 using Tapatalk

How short is stupid short? It was cut down to 15" and suppressed with a graystone 3k by the previous owner.

Originally Posted by mimms2

Those aren't that flat and your FP strike isn't cratered, though looks pretty variable but could be the angle of the photo.
As you were.

Glorious, cheers mimms2

Greetings again Strider B,
I'm with Minimms2 again. 44 grains of AR2206H is well below max of 45.5 grains for the 150 grain BT even in the Federal cases which have less capacity than the Winchester ones that Hodgdons used. Also I don't think your head space is excessive as there is no riveting as there would be on a rifle with more head space. If you are full length resizing it would still be wise to check for incipient head separation each load after the third. 15 inches borders on stupid short for this old fudd but it seems to work for you so relax and enjoy.
Grandpamac.

I wouldn't be too worried by those primers, they still look to have rounded edges.

Federal 150gr blue box was IIRC around 2820fps from my factory lenght Sako at near 22", it and another Sako and 3 Tikkas I have used the same ammo in all had primers that looked like yours but had occasional swipe marks from extruding case head brass into bolt recesses.

That is all first firing of factory ammo in factory rifles.

Id say you are near max for that combination but wouldnt be too worried, neck sizing only will probably improve primer appearance but fed brass is soft and I would be surprised if bolt swipe didnt appear after one or two neck sizes and it has fully conformed to chamber.

Still safe tho....fed brass and primers are soft and show signs early.

it never fail to amaze me in this modern internet enlightened enviroment that folk who reload STILL DONT READ A MANUAL....... you have a load from a manual....most if not all have a start load and a maximum load....you ARE SUPPOSED to start low and work your way up....UNTILL you know rifle and what it likes/doesnt like.....nearly EVERY reloading manual will have two cautions in it
nearly every source of reloading data will have the same two warnings

data was safe in test rifle...all rifles are different
start low and work up.

a good example of this is my .270 Vs RUMPYs one....his loads would be fine in mine...my loads would quite likely blow his rifle up..... my rifle HAPPILY sits 2grns above maximum of most manuals.......his flattens primers and gets sticky bolt 1-2grns BELOW MAX....
his has short throat...mine has longthroat and what appears to be a loose barrel..both shoot sub moa and both kill animals.