My understanding is that the only modern ARs that might have problems accepting 5.56 are those with match-grade chambers. The tighter fit between cartridge and chamber could result in a casing getting stuck due to the greater neck expansion of the 5.56. Since the Saiga isn't machined to that level of tolerance, it shouldn't be a problem.
Exploding rifles should only be a problem if a squib leaves a round stuck in the barrel. In that case, I'm guessing you'll have more problems if you're using a cast receiver than a stamped, milled, or forged receiver.
But no. None of this is from the m