I am putting together a parts list for my Form-1 build. I am going to do a 300 BLK and also a 308 and I guess I will short barrel it too while I am at it. I am going to add a Gemtech ONE later after I recover form the first out lay. (Caliber Rated: 300WM (24" or longer barrel), 7.62, .308, 5.56 (7.5" or longer)) since it will run both calibers and much much more.

I am looking to put a Geissele SSAE in the 300BK I would welcome comments and suggestions on the trigger selection. Alas the 308 will have to live with a mil-spec to start with. Be going with a 8" 1-7 twist on the 300.

Also any problems or comments on putting a 10.5" on the 308?

Trigger:  1st question is what do you plan to do with said rifle?  That will dictate the correct trigger.

308 SBR:  Blast.  Not as much of a problem if you run a can, just make sure it is rated for an SBR.

I can't come up with the data but I have read that you shouldn't go below 12.5" for a .308.  I was looking at SBR'ing my SCAR 17 at one point and that was the shortest recommended length.
Sure some people take their 5.56 below 10.3" and it shoots just fine so YMMV.