Been fighting with my Ruger that I rechamber to 357 max, using a custom reamer that I had Dave Manson make for me. I dimensioned it for use with the lyman 358627 bullet. Also been shooting some Lee 258-180gr fpgc bullets along with Remington 200gr rn bullets. Needless to say, the groups at 100yds would be acceptable for OOO buckshot at 10 yards, but not the rifle. Started low with 4227 and Lil Gun and got about 12" patterns that slowly went down to 6" patterns as the powder charge went up. With the Lee bullet, I finally would get 3 in a nice cluster, then 3 in a nice cluster about 4" away, then all over the place. The Remington bullet finally got down to around 4" group. Don't know velocity as I left my crony at home both times
Finally, with a near casefull of H4227 and the Lyman bullet seated as deep as I could ( a really compressed powder charge), I would chamber the round with the bullet in the rifling/leade about .050", and shot these for a sub-MOA group. Don't know if it was the bullet seated in the rifling (like breech seating) or because of the compressed charge and bullet in the leade that I got such good groups.
Would this indicate that maybe I need a hotter primer? I am currently using Remington 7 1/2 br primers. I also have some WW SR primers and some Fed SRmatch, and I might have some CCI sr primers, maybe some sr mag primers (about 25yrs old) to try. Thoughts anyone (especially Hobie--I know you like this cartridge--so do I) Thanks