I have a m70 .308,I changed the barrel to 220 swift,everything works except the magazine,it will cycle ok if only one shell in magazine,if 2 shells are in,it will not pick up the shell,what modification is neccessary for it to cycle with more than one in mag..lll308
The problem you're having is probably due to the .220 being a rimmed round whereas the .308 is a rimless round. You'll need to modify the magazine box feed lips and/or the follower. I'd recommend you let your gunsmith figure it out. I forget what the formula is for magazine box width but I believe it's 1.6 x cartridge diameter.
Sometimes you earthlings REALLY amaze me!