Leapers mount installation on m305

[Will I Am]

I can't get the mount's screw into the receiver, The screw is too big for the hole in the receiver, what is the correct size of thread do I need in my receiver?

 

[45ACPKING]

the norc hole and thread size should be the same as a m1a or usgi receiver's hole/thread...... if the mount is intended for this purpose.... it should have come with the correct bolt...... can you send it back?...... is this mount meant for airsoft? as they are made to same dimension but the bolt can be different

 

[Will I Am]

I messed up the screw, and the threads in the receiver. I beleive the hole was undersized, I'm gonna try retapping with 12-32 extra fine and see if that changes my mess up....