Today i went to the range. i was testing a new build.
12.5 in. 7.62x39 faxon ar barrel socom profile, and was shooting suppressed. i was shooting 5 round strings, let it cool 3-5 min. i was getting good groups with a 1x4. after about 40 rnds., my groups started rising. buy the time i shot 60, it was about 4 in high, but still tight. never had this problem with my 16 in. 7.62x39 DPMS heavy barrel. you think the socom profile is to "thin" for a 7.62x39? i don't have this problem with a 11.5 in 556. todays temp was about 82.