usmc1974 Posted October 14, 2014 Share Posted October 14, 2014 I was thinking about building a 10" ar15 pistola. I was wondering about what the average velocity from a standard 55 grain ammo. Thanks B Link to comment Share on other sites More sharing options...
MWP Posted October 14, 2014 Share Posted October 14, 2014 It differs per barrel, and ammo. I'd say an average loss from 16" would be around 300fps. Link to comment Share on other sites More sharing options...
HRider Posted October 14, 2014 Share Posted October 14, 2014 I chronoed 55 gr Aguila out of a Colt 20" 1/9 barrel at 3055, 3130 out of my 18" JP CTR-02, 1/8 twist and 2621 out of my 10.5" 1/7 AR, all on the same day. That is the only load that I have chronoed out of the 10.5" gun, so I don't have any other direct comparisons. Hurley Link to comment Share on other sites More sharing options...
Flash74 Posted October 14, 2014 Share Posted October 14, 2014 (edited) For 223 ammo (AR223) I get around 2600 fps out of my 10.5" barrel. 556 ammo (AR556) is about 80fps higher. Figure about 50fps lost for each inch of barrel length less than 16". The ammo listed above is factory Federal. Edited October 14, 2014 by Flash74 Link to comment Share on other sites More sharing options...
usmc1974 Posted October 15, 2014 Author Share Posted October 15, 2014 Thanks guys that is what I needed to know. Link to comment Share on other sites More sharing options...
steviesterno Posted October 15, 2014 Share Posted October 15, 2014 unless you go 300 BLK, which is designed to use all it's powder around 8" or so. any longer barrel and you start losing velocity, from what I was reading. Link to comment Share on other sites More sharing options...
Alaskapopo Posted October 16, 2014 Share Posted October 16, 2014 Even the 300 blackout is not getting complete powder burn I 8 inches. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
mulrick Posted October 16, 2014 Share Posted October 16, 2014 Even the 300 blackout is not getting complete powder burn I 8 inches. Sent from my iPhone using Tapatalk Yeah i think it's 8.something... 8.5 is the min, and 10.5 is better. I own a .300blk pistol and it is a riot to shoot, however... I am not all that impressed with 5.56 out of 14.5 or less. Sorry, I know that makes a bunch of people all butthurt... I carried a MK18 for 4 years, it maneuvered well in tight places, bulkheads, etc. But given the opportunity, I'll take a longer barrel any day. Link to comment Share on other sites More sharing options...
Alaskapopo Posted October 16, 2014 Share Posted October 16, 2014 Ammo makes a big difference. 75 grain tap does much better from short barrels than 62 grain ss109 Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
gunther Posted October 19, 2014 Share Posted October 19, 2014 (edited) M855 Avg Velocity 62gr 20 in 3000 fps 18 in 2900 fps 16 in 2800 fps 14.5 in 2700 fps 12.5 in 2650 fps 11.5 in 2625 fps 10.5 in 2600 fps just a guide, but you can see the trend Edited October 19, 2014 by gunther Link to comment Share on other sites More sharing options...
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