You might have messages disabled on your account? Because I can't send you a PM either. Anyways, 7SST is no problem in a rem700 SA, that was Rich's entire purpose for the design, he wanted the length to fit in a short action, but I don't know anything about AR10s.
@elkaholic any insight on running SSTs in an AR10? I think your bigger challenge on running in an AR platform might be the cartridge diameter more so than the length, but I'm just guessing. I know there are some short mag ARs out there, but seems like every AR10 I've ever encountered is a standard diameter cartridge (308 family). Rich may reply with more insight.