Why can't gunmakers just make a universal thread size for all drilled and tapped recievers? With that being said, I finally found some weaver mounts that will line up with the predrilled holes in my reciever. But the screws to mount them are to small for the holes and I need to find the correct, thread. Anybody know? Thanks

There are 2 standard sizes for scope mounts on rifles.
One is 6x48 and the other is 8x40. Yours is probably 8x40 if the screws with the Weaver mount were too small. You will have to have the proper base for that screw size or open up the holes in the mount you now have.