for those that may know some of the more grognard history of the M16-A1 i got a question 1in12 or 1in9 twist rate with 55 grn fmj. what is more effective the moment the bullet hits the target as in destablizing and the bullet taking wierd paths or going to bits?? max effective range 300yards. need enough accuracy with fmj to hit yote sized targets at 300 yards. which twist rate will get a 55grn fmj there. what was the issued twist rate in the M16-A1 in the period from 1967-1980 when they started issueing the A2 with the 1in7. ive come across a lot of conflicting info on this. thanks.