Re: .22-250 AI
I'm thinking over the same thing. My .22-250 is (over) due for freshening up too and a fast twist AI has it's attractions. I have a .30-06 AI and know the case forming drill, so, IMHO.
Pros (only two):
Less case stretch
Fireforming second-rate ammo (velocity-wise) to get brass wastes components and barrel life.
Factory ammo loses some velocity if fired instead (and brass has to come from someplace), so one needs two sets of drop data
Enhanced fouling due to larger charges of slower powders
Less barrel life (Gotta pay to play)
Even though I shoot several wildcats, I don't like fireforming in general. Fireforming takes on a whole new PIA factor when the performance increase is marginal, as with the .30-06 AI version. If you get 5 shots per case, then fireforming will be 15-20% of your barrel and brass life - gotta really be worth it . . .
I would like the aspect of heavy (75/77/80 grain) bullets at good velocity. I shoot quite a bit at longer ranges and seldom shoot my 12" twist/55 BTHP .22-250s beyond 500 yards, 400 if it's windy. The drop is just so bad with lighter bullets, even at high initial velocities, that range is drastically reduced. I've been shooting heavier (68/69 BTHP) bullets in a 20" AR15 and at 600 yards, they need half the wind my .22-250 with 55s.
Fouling with slow powders can be a huge PIA, and the carbon fouling sometimes requires desparate measures. I'm shooting Retumbo in a .243 behind 105 & 115 grain bullets and it needs to be JB'ed every few hundred rounds to keep the buildup under control.
The beatings will continue until morale improves.