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Posted: 6/19/2004 5:56:49 PM EDT
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I have some DNL marked DNL 223 REM on the head. I think it is from 83. Anyway, it short-cycles with my 16" rifle but functions fine in my 20" rifle. Why? I roughly measured the the length of the gas tube and it is about 21cm in the 16" and 33cm in the 20". If the gas tube is shorter in the 16" barrel, I would think that the pressure bleeding off the barrel would be higher than in the 20" barrel. Is it because even though the pressure is lower in the 20" barrel at the time the bullet reaches the gas tube 'exit', the pressure is kept up over a longer period of time until the bullet reaches the muzzle at which point the pressure drops? If I'm using the wrong terminology, please correct. I'm just shooting up this ammo and only have about 500 left. I also have a battle pack from 83 that short cycles as well and about 250 rounds of that left. I am stocked with Q3131A for SHTF on strippers/mags. Thanks. |
Correct. The gas has more "dwell time" between the gas port and muzzle to enter the gas tube and cycle the action. This is one reason (maybe the only reason?) why the dissipator was created and why short barrels with long gas systems often have problems. |
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That's ok, I plead stupidity. The dissipator wasn't created to address that problem, but it's design did. The dissy was made to get a long sight radius from a short rifle. A dissiptor is a 16" rifle with a standard 16" gas port, however the normal gas block has been shaved off so that handguards can fit over it. 20" handguards are used and a full gas block (with front sight) is put on the end of the rifle. This gives you a full sight radius. If the sight was connected to a gas port then the rifle's dwell time would go down to about 2"...far too short. So, basically the front gas block is non-functional except as a sight and the REAL gas block is hidden. |
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