I just picked up my 6.5-284 from my gunsmith this past weekend. He did a bit of load testing with it and I am ready to start fine tuning some loads using once fired cases. He, and others, recommend bumping the shoulder back 0.002-3 when neck sizing. He built the chamber for a tight fit on the Lapua brass and I am measuring about 0.003' difference from unfired to once fired cases when measuring from base to shoulder using a tool he made using the barrel trim piece and the chamber reamer. I have a Redding Type S bushing sizer die that is chamber matched. The problem I have is that I cannot get the shoulder to bump back at all. In fact, I get about 0.001-2 growth when I try to bump. I have tried the standard Redding shell holder and all the different sizes of Redding competition shell holders that incrementally change the amount of headspace. I started with the sizer die 1 full turn from touching the ram at full throw,recommended by Redding) and even tried the sizer die touching the ram at full throw. I have the Redding UltraMag press so I plenty of strength to size the cases. Any ideas as to what is going on here? My gunsmith buddy is a bit perplexed at the moment as well.
Best,
Archerross
Best,
Archerross