usmc1974 Posted December 26, 2016 Share Posted December 26, 2016 I was thinking about building a AR pistol in 5.56 what kind of velocity's are ya'll getting in a 10 vs 8.5 barrel with 55 grain fmj. Thanks B Link to comment Share on other sites More sharing options...
HRider Posted December 27, 2016 Share Posted December 27, 2016 I cant totally answer your question, I don't have an 8" AR. I have chrono'ed Aquila 55gr from my 18" JP (1-8 twist) and my 10.5" Rock River (1-7 twist) on the same day. The JP averaged 3130fps, the Rock River averaged 2621fps. I hope that this helps. Hurley Link to comment Share on other sites More sharing options...
usmc1974 Posted December 27, 2016 Author Share Posted December 27, 2016 it does thanks Link to comment Share on other sites More sharing options...
Nathanb Posted December 27, 2016 Share Posted December 27, 2016 My 10.5 sbr was in the 2600 range as well. My 12.5 sbr in 308 was in the 2200s iirc not apples to apples but someone may want that. Link to comment Share on other sites More sharing options...
usmc1974 Posted December 28, 2016 Author Share Posted December 28, 2016 (edited) 2550 2600 is what I am generally finding out for 10 inch so that is what I think I will go with. that comes out to about 800 to 900 foot pounds of energy. much better then a 357 so I am good. thought about a 7.62x39 but this way I use all the same rounds and mags. at 3 minutes he gets a 10.5 barrel Edited December 28, 2016 by usmc1974 Link to comment Share on other sites More sharing options...
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