Thread: My 260AI Load Development Begins

With my AI (6.5SM AI) I find with the 40 dgree shoulder and the only slight case taper I go around 5 firings b4 chambering is a concern and FLS becomes required. Virtually zero brass flow.

Re base measurement - yep did that, took mic to range, recorded movement, if any. Analysed the hell out of it. Discarded checking in the future.

There was a good article on Accurate Shooter quite a while back debunking using base growth as the ultimate pressure guide.

Some chambers (yours would not fit into the category I assume) are a bit "sloppy" so you can get what appears to be excessive base grouth after 1 shot with safe pressure loads. Subsequent loadings of the same brass at the same safe pressures, neck sized only, would see little or no movement. Panic over.

Rule of thumb used to be anything around 1 thou and panic. Or anything that continues to grow.

I have also seen very loose primer pockets with in some cases no proportional change in base diameter.

On my AI I gauge the primer pockets b4 each load as I did have one load that opened up the primer pockets. Depends if you are running hot or not. On the Swede (6.5mm) I get 3010 fps with 142gr projectiles but did take it up to a lot faster/hotter than than that - hence BIG primer pockets. Very annoyed with myself given the effort required to make brass.