338 Lapua - case expansion and sticky bolt ?
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. I seem to get similar results at even lower charges. 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. After 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 (seems like too often). The rifle is very accurate with these loads, but I'm scared to try and get any more velocity out of it. As it is, the sticky bolt extraction and swelled cases that won't chamber after one firing are causing me grief/concern.
Any thoughts or suggestions? thanks