338 lapua - excessive case expansion and sticky bolt ?

[depopulator]

I had a custom 338 Lapua built in 2009. I am having ongoing problems with sticky bolt and difficult extraction, even with mellow loads of 87.0 grains of RL 25 and 87.8 H1000 under 300 SMKs (seated -0.040" from lands) that go around 2700 fps out of my 28.5" barrel. From my research, this is by no means a hot load, but all indications are that I am getting excessive pressure. Apparently, the cases (lapua head stamp) are expanding larger than the chamber after firing.

I have been resizing the brass using a redding body die to set the shoulder back around -.001 to -.002" measured with Sinclair bump guage) while ensuring the case head is sized as well. When I FL size the case head, it "pops" when I raise the press handle past the case head. After FL resizing, the brass chambers without issue. However, after one firing of the FL sized brass, the case/bolt sticks, often requiring some extra force to lift the bolt past the top of the extraction cam and sometimes even when extracting the bolt. Feeding once fired brass will typically lock the bolt before fully chambering the round, and it is very difficult to extract, often requiring hammering the bolt the open it. Only neck sizing is not an option at all. I trim all brass a 2.714" every couple of shots. The rifle is very accurate with these loads, but I can't get any more velocity out of it, and the sticky bolt extraction and swelled cases that won't chamber after one firing are causing me grief/concern.

Any thoughts or suggestions? thanks

 

[TonyR]

You might want to check the length gauge. If the necks are too long, they may be pinching the bullet at the case mouth. The gauge is cheap and easy to use.

http://www.sinclairintl.com/.aspx/pid=32925/Product/Sinclair_Chamber_Length_Gage

 

[depopulator]

I ordered the length gauge last night, but I am sure I am trimming to proper length based on the reamer specs. Tnx

 

[people]

That does not seem too bad to me. Your rifle is just tighter than most. I have an AR-30 in 338lm. I am using more powder to get almost the same speed.

 

[glbpmc]

Check the outside neck diameter and ensure it is not causing too much neck tension. I personally saw one of these with the same type problem and after turning the necks for .002 neck tension the same charge weight showed no sighn of pressure at all. If this does not work keep asking it is going to be simple when you find it. Good luck

 

[338 dude]

I had a custom 338 Lapua built in 2009. I am having ongoing problems with sticky bolt and difficult extraction, even with mellow loads of 87.0 grains of RL 25 and 87.8 H1000 under 300 SMKs (seated -0.040" from lands) that go around 2700 fps out of my 28.5" barrel. From my research, this is by no means a hot load, but all indications are that I am getting excessive pressure. Apparently, the cases (lapua head stamp) are expanding larger than the chamber after firing.

I have been resizing the brass using a redding body die to set the shoulder back around -.001 to -.002" measured with Sinclair bump guage) while ensuring the case head is sized as well. When I FL size the case head, it "pops" when I raise the press handle past the case head. After FL resizing, the brass chambers without issue. However, after one firing of the FL sized brass, the case/bolt sticks, often requiring some extra force to lift the bolt past the top of the extraction cam and sometimes even when extracting the bolt. Feeding once fired brass will typically lock the bolt before fully chambering the round, and it is very difficult to extract, often requiring hammering the bolt the open it. Only neck sizing is not an option at all. I trim all brass a 2.714" every couple of shots. The rifle is very accurate with these loads, but I can't get any more velocity out of it, and the sticky bolt extraction and swelled cases that won't chamber after one firing are causing me grief/concern.

Any thoughts or suggestions? thanks

My load is n-570 88 grains a 300 Berger Elite Hunter cci 250 primer and Lapua Brass 2730 FPS with no pressure signs