Similar issue, my son had snapped a screw off in his accumark 30-378 yes the front screw that goes into the barrel threads.
Not trusting a gunsmith he sent it back to weatherby in Cali the maker of the rifle - beware - first the imbecile walked the drill of the receiver putting a nasty mark in the rec & barrel - next he drilled the screw off center and the sent it back - now the rifle needs a receiver or the bolt holes drilled back on center and opened up to the next size - I was a great fan of Weatherby customer service but the last 2 rifles the ruined and getting them to make things right is a choir. I think the 6-xx screws can be opened to 8-40 we are looking at a smith in Pa "http://www.montourcountyrifles.com/" I am hoping they can fix the mess my son has on his hands.