I bought a new bolt handle for my 7.62x39 RARR. I took the bolt apart and attempted to put the new bold handle in, it was too large. I then decided to try it in the 556 RARR and it went right in. The 556 is one of the new AR 15 mag designs. I am wondering if different calibers, or different models take different bolt handle sizes. Any info on this would be appreciated.