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Posted: 12/20/2012 11:00:38 AM EDT
| What controls headspace and how can you change it? I realize this may be an in-depth discussion so maybe someone can direct me to a source for my answer. |
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Headspace on the AR-15 is controlled by whether or not the upper receiver and the barrel are both within spec tolerances. As far as I know, if the headspacing is off, it needs to be sent back to the factory for reworking as the barrel nut just holds the barrel tightly flush against the upper receiver...
Many users don't even check headspace on their new rigs, because if all the parts are tight and in spec, the headspace should be perfect. Those of us more paranoid/careful users at least throw in a field gauge to ensure correct headspacing on new builds before firing though. |
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Unless you can do it yourself changing a barrel extension would probably not be cost effective.
From what I have seen new good bolts will vary a couple of thousandths in headspace on a given barrel. In the case of a bad or worn bolt changing bolts may get you somewhere. |
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When we had M16s/M4s come in and fail headspace, first thing we'd do is use a brand new bolt we kept as a control. Often times the combo of a worn bolt and worn extension would fail, but swapping a new bolt would pass. It all comes up to tolerance stack. If it fails with a new bolt, send the barrel back, or if it's an old barrel, time for a replacement.
Semper Fi |
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