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Posted: 2/16/2009 1:08:23 PM EDT
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Another newbie question.
I recently bought my first AR, an AR 22LR. I just removed the handguard and was suprised to not see a gas tube. Is the typical AR 'gas action' not present or required with a dedicated 22LR upper? |
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Quoted:
Another newbie question. I recently bought my first AR, an AR 22LR. I just removed the handguard and was suprised to not see a gas tube. Is the typical AR 'gas action' not present or required with a dedicated 22LR upper? Nope, no gas system required. A .22LR does not generate enough gas to operate a conventional AR or FAL type of mechanism. They are blowback, like a Buckmark pistol or a Ruger 10/22. The bolt is held shut by spring force and the static inertia of it's own weight. This is overcome by the gas pressure generated by the cartridge discharge, but the spring power, and the inertia of the relatively heavy bolt resist the increase in gas pressure long enough for the bullet to leave the barrel before the bolt begins to move backwards. This is in reality measured in micro-seconds. Once the gas pressure from the fired cartridge overcomes the spring/mass force resistance, the bolt is "blown back" to extract the fired case. The spring then forces the bolt forward again, picking up a fresh cartridge from the magazine as it goes. Nice and simple, but it demands considerable precision of manufacture and it can be a PITA to get the spring force correct and the bolt operating freely. |
| Being a dedicated 22, there is no need for a gas tube. It will run considerably cleaner without a gas system. You won't have the burnt powder coming back through the gas tube into the 22 bolt assy. I don't have any dedicated uppers, so I leave the gas system intact on my .223/5.56 barrels and deal with a little extra cleaning. |
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