Issue with primers backing out

[bhoges]

Im shooting a Nesika Model K repeater with Shilen barrels. Im using Lapua 260 brass,federal match primers, 4350 with 120gr Sierra's. My problem is the rifle shoots awesome but even with light loads the primers are backing out. I tried 40.0 grains today which ran only about 2675fps. My smith says the brass could be the problem. That its been sized too much and the shoulder is too far back. So far I have just used new virgin brass right out of the box. No resizing just shot it. Any ideas? At 200yds Im getting .589 groups which is pretty damn good.

 

[Bear24]

Do you have a head space gauge to compare the fired brass to the new unfired brass?

 

[bhoges]

Havent done that yet but the smith I go to knows what he is doing. Really doubt he would have excessive headspace. He has build ab out 5 rifles for me. They all work fine. I might just try some factory ammo as well and see if it happens.

 

[milo 2.0]

How far are they backing out? A pic would really help. I uniformed some pockets way too deep, now they back out and flatten, ugly, but I still don't consider it pressure, and am going to continue to use them.

Size them and load them again and see what gives.

 

[milo 2.0]

Just say your chamber is reamed long, you've already stretched your brass, utilize the extra case capacity and move forward. Limit the amount of brass you run through it, like 200 pieces.

 

[biffj]

You may be loading too light. Sometimes a light load is enough to back the primers out but not enough to have the case sit back and reseat.....Try some full power loads and see if the primers are seated after firing.

Frank

 

[Dan Newberry]

Just say your chamber is reamed long, you've already stretched your brass, utilize the extra case capacity and move forward. Limit the amount of brass you run through it, like 200 pieces.

this will work. the primer won't back out next time, unless you bump the shoulder too much. try neck sizing...

 

[bhoges]

Figured it out. I won't mention the smith but I had excessive headspace. Off by .012 thats pretty bad. I pulled the barrel and went with my backup. Pretty pissed about the poor work.

 

[Eastbay]

Are you crimping them?

 

[Rprecision]

Figured it out. I won't mention the smith but I had excessive headspace. Off by .012 thats pretty bad. I pulled the barrel and went with my backup. Pretty pissed about the poor work.

That's quite a bit,

Its hard to let that one go. That would have closed on a no-go and then some

 

[bhoges]

Yes it closed on a no-go and we added tape to see how far extra it was out. My other barrel was in spec but on the outer edge. I think Im going to cut them both and have my buddy redo both.