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Posted: 10/16/2011 8:18:30 PM EDT
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I'm looking to buy a 16" barrel but have some questions on some of the terminology. What does mid-length mean? Is there a full-length option?
I just dont understand what mid-length means. Any help on this would help. |
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Carbine: short gas system (M4, best for 11.5" to 14.5" barrels)
Rifle-length: long gas system (A2, 20" barrel) Mid-length gas system: in between the two above. The gas system determines where the gas port is in the barrel. It also thus determines where the gas block goes, how long the gas-tube is, and most likely impacts your handguard selection. The hole for a carbine length is around 7.5" down the barrel (going from the chamber end). Rifle length is around 12". Mid-length is around 9.5" down, though I think Noveske has a proprietary length of their own. The gas port is ideally as long as possible, but must meave enough room between the gas port and the muzzle (the space where, while the bullet travels down it, gas from the fired round can go through the gas hole but is still under pressure because the bullet has not left the muzzle) to cycle the action, generally about 4-5". Why should it be farther out? The gas loses pressure the further down the barrel the bullet goes, so the carbine system is sending tremendous pressure through, the mid-length is sending considerably less, and the rifle length is sending the least pressure. Higher pressures can increase recoil felt and wear/tear on the upper's internals. For a 16" barrel, your ideal length would be a mid-length gas system, but there is nothing all that bad about a carbine length gas system on a 16" barrel. Note, you want a handguard system that matches your gas system for length.... carbine handguards or FF forend for a carbine length gas system, etc. However, you can have a handguard/forend that is LONGER than your gas system if you use a low-profile gas block (no front sight, no rail on the gas block). Many people choose this option, with at least a rail along the top (12 o'clock) to mount a flip-up sight for the front sight. Good luck, hope this helps. |
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