Nine Toed Omar
I haven't tried IMR3031 in my Rem 700 Mtn LSS 7mm-08, but here is a list of loads I've worked up so far. (Please take note of the loads that are over book max!) You should get a little better velocities with the 24" barrel of the SPS vs the 22" barrel of the Mtn LSS.
I just pickied up this rifle this past spring and love it. I used the Speer 145 HotCor's to take a decent 8Pt this season. Shot was at about 75 Yds, was a complete pass through, and left about a quarter sized (maybe slightly larger) exit hole. Deer went about 20 Yds and dropped.
As far as the 7mm-08 AI is concerned, the 7mm-08 is already a very efficient cartridge and although I can't say for certian, I just don't think that you would gain enough by going AI to justify the cost and the trouble of fire forming, etc. I'm sticking with the plain old 7mm-08!
You should get the best accuracy with neck sizing only. I haven't shot a single factory load in my gun and neck sized only for all the loads listed above. You will however need a full length sizing die (in addition to the neck sizer) so you can bump the shoulder back occasionally as needed. I have found that I needed to do this after about 7 or 8 reloads.
What kind of scope are you putting on your SPS? My "Hunting" scope is a Burris Fullfield II 3-9X40 w/Ballistic Plex reticle and have got to say that the Ballistic Plex bullet drop compensating reticle is just awsome and very effective. My "load development/range" scope is a Simmons Whitetail Classic 6.5-20x50 w/AO. I put on Leupold quick release rings & bases that allow me to switch scopes as needed.
Good luck with your 7mm-08 SPS and be sure to keep us updated on how it shoots.
Make your first shot count!