Question: Currently at 60ish rounds through the barrel. With barrel break in and in warmer conditions, is it reasonable to expect 30-50 fps gain?
Your comments, experiences, suggestions welcomed.
YMMV and happy shooting
In my limited experiences , 30-50 fps gain in speed should be expected. Possibly / probably more as I've experienced. This particular barrel is a Shilen select ratchet rifling , finished at 24", mounted to an ARC Nucleus V2 via a barrel nut system. I used the Savage small shank nutted system over having my smith do a direct fit so I could have a little control on head spacing if I so desired. My first foray into 6 arc , was with an Odin 18" gas gun and I saw around 40 fps increase in speed from new through load development. I didn't obtain speed and accuracy goals with that tube using primarily LeverEvolution , so it was replaced with a Rainier Ultra at 22". The Rainier round count is less than 150 , so not enough data to comment on that one.
As stated above, I saw near a 100 fps increase in speed with same lot of powder and projectiles . Dunno if it was a combination of environmental and or loading / cleaning procedures causing the ramp up. Varget is pretty temperature stable , and has been one of my favorite powders across many calibers for years. I have never experienced such a ramp up in speed without explanation. I do know once I reached into the high 2800s into the 2900 area that load fell apart and opened up , and the brass was getting beat. Also on a very important side note , I had miss typed in the posting you quoted. The loading was 27.9 - 28 grain , NOT 28.9 grains as listed in post # 8 , apologies to all.
IMO some important advice is to use Alpha or Starline brass. IME it seems as we need to be near the top of the loading limits , for the 6 ARC to shine . The Hornady stuff will have loose primer pockets after only one or two stout loadings.
Life and other interests have given me the time to continue working with combo, and will explore more and report back.
