Just my 2 cents worth.
Recently a gunwriter layne Simpson I think decided to build a 250 savage AI, for brass he just used 6mm credemore case necked to 25 cal. No fire forming just load and shoot. Me thinks the credemore just reinvented the wheel. Is it the 6.5 credemore or the 6.5/250 savage AI.
Years ago 1982 Aussie gun writer Nick Harvey and your own les Bowmen attended a Remington seminar. Both were presented rem 700s in 257 Roberts. Nick had his long throated so he could SEAT bullets to match the chamber 3inch.
He developed loads pushing 3,200fps with a 100gn and close on 3,000 fps with a 120 gn. He corresponded with Les about his result, he didn't believe Nick until he tried it himself and got the same results. Bowman approached Remington about upping their anemic Roberts loads to real world pressure but was declined in difference to all the so called weak actions. As Harvey points out the Roberts was introduced in rems 721 action not a weak action.
Anyway that's my 2 cents of history may the 25s rule.
I know the above is fact because Nick Harvey wrote an article about it in the Australian sporting shooter Mag and I have spoken with him personally about it he love his Roberts.
Layne must have magic dies. Considering a 250 Ackley has a 40 degree shoulder and the 6mm Creedmoor has a 30 degree shoulder.
PS: Give spell check a whirl.
