I have been shooting the 22-250AI for about 20 years (gave up on the standard version many years ago). I have tried about every powder, bullet,barrel combo that there is.
My favorite is a 1-8" twist barrel with a 5R or 5C groove, even a 6 groove works well. the only bullet I shoot any more is the Berger 80gr VLD.
as for powder the two stand outs are RL19 and IMR 4831
In my experience the worst combo I ever tried is what Seafire shoots, a 1-7" with RL15
Based on that post, and one other on 243s.... I picked up a pound of RL 19 yesterday ( I've been out for a while...) so I will be trying it once again... and compare its velocity results with my normal GoTo Loads...
My barrel is a Pac Nor Reject.... It was put on a 223 originally.... I ended up giving the rifle to Mike Bellm, after putting the factory barrel back on...
The rifle was chambered and installed by John Noveske, before he got famous....he gave me the barrel and threaded, chambered and installed it for $75... he rechambeed it for the 22.250 for $25..... I use to send business his way, so it was a thank you from him at the time...
its still one of the most accurate rifles I've owned tho...
so I have no idea how many grooves it has.... never saw a need to question it it, based on its accuracy...
it does like 75 BTHP and 80 A Maxes a lot better than 75 A Maxes....just picked up some of the new 80 grain ELD-M to try in it....will start with the RL 19...
Thanks for the reply!