my ai forming,24" barrel,55g is 3850 fps with 5/8" groups or better, yet to find the down side of the ai after owning 8 regular 22/250's over the years
Keith and I built our first 22-250AI's around '89 or '90 after an article by Ross Seyfried. At that time a pretty standard fireform method was to fill the case with W760 to the mouth and seat a Sierra 55BTHP. Sounds crude but it worked fine and was surprisingly accurate. Even in a cut-back rechambered Rem chromoly barrel the velocity was about 3850 with a 55. I formed 900 cases that way. BTW-I'd used that same barrel as a std. 22-250.....most accurate load with the same W760 powder and Sierra 55BTHP was at 3550-3600.....not the fastest and certainly not high pressure, but the most accurate.
