Home Forums Hunting & Shooting Gunsmithing Xbolt scope mount screws...3 of 4 too short...need new ones..??!

I recently picked up a like new browning X bolt with rings and mounts attached. I just started to mount a scope and found 3 of the four bolts threads holding the rear mount were stripped. I found that the threads in the rifle were good. The problem was that the 3 stripped bolts were 30 thousanths shorter than the bolt that held tight. It seems that the shorter ones only allowed for one or two threads to grip and must have been easily stripped. 3 bolts were .380", the longer bolt that works in each hole is .410". My question is ....What is the easiest way to fix this? Also, what size screws do I need to order.. Where can I order them from? Here are some pics to show the screws. Thank you for any guidance you can provide... John