Interestingly enough I never have had a problem shooting ARs for groups off the bench or otherwise.
I konw a lot have had issues though. And I do know that if I shoot off bench, I can get worse groups the further out the front rest is placed under the forearm. But I never put it way far out with bolt guns either.
As to bipods, IMHO I"ve always had best luck with a bit of pressure on them.
