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Posted: 1/5/2014 3:21:36 PM EDT
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A while back I posted a thread about some velocity differences I was seeing in two different 16" barrels, but it was not very conclusive. I went out and re tested under more controlled conditions and still came up with a smaller than expected difference. What I'd like to do here is collect measured velocities. It won't be pure apples to apples given the variables but it should give us a pretty good idea as to what barrels have a higher velocity.
My hypothesis is that chrome lining, and faster twists rates slow velocity meloniting, slower twist rates, and certain types of barrel construction increase velocity Discuss and please contribute your findings, but only actual measured data please |
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Federal XM193 (advertised 3250fps)
45F 3200ft 20rd averages Alpha Shooting sports 16", 1:9, melonited, midlength - 3109fps Daniel Defense 16", 1:7, chrome-lined, carbine - 2943fps ETA: So in my most controlled testing yet, the theoretically slower barrel was indeed slower, but only be ~60fps (on average) |
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Faster twist rates use more of the energy from the powder's combustion to turn the bullet than slower rates. You are correct there.
I think you need a third variable in there though: compare NON-chromed, NON-Melonited barrels to chromed and Melonited barrels. I think you'll see plain steel barrels slower, chrome in the middle and Melonite fastest. Another variable will be "traditional, groove-based" rifling versus polygonal rifling. The theory from the polygonal camp is that the less severe shape of the rifling should lead to higher velocities for a given load. I haven't seen where anyone has actually tested that though. I'm looking forward to seeing the inputs you receive and what conclusions can be gleaned from them. |
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Quoted:
Federal XM193 (advertised 3250fps) 45F 3200ft 20rd averages Alpha Shooting sports 16", 1:9, melonited, midlength - 3109fps Daniel Defense 16", 1:7, chrome-lined, carbine - 2943fps ETA: So in my most controlled testing yet, the theoretically slower barrel was indeed slower, but only be ~60fps (on average) I'm not that great at math, but I'm pretty sure the difference with your numbers is 166 FPS |
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