You will NOT be ready for 250 yards very soon, maybe never. Braggart!

Slow down and do everything - EVERY THING - as consistently as you possibly can every time. Listen to these guys carefully about powder charge and don't try to hotrod the loads. Give your rifle a chance by eliminating yourself as the problem.

Some good sandbags (which you can make yourself from old jeans legs) should give you an adequate and stable shooting rest on any good bench. I prefer bags to any rest I've ever used. Work on that flinch!