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Posted: 11/18/2007 1:32:26 PM EDT
Sorry if this has been asked before. I have a rifle that the cam pin is begining to show a gouge wearing into it. Is this normal? The gun has 2-3K rounds through it. It is a rifle that I recently SBR'd to 10.5 and does not cycle reliably. My main question is; if the cam pin wear or whats causing the cam pin to wear make the rifle not cycle
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Normal wears of the cam riding the carrier slot at lock/unlock. As for the cam pin wear, and the rifle SBR'd, chances are they are not related, and either you have a problem with the gas port being too large causing over function (the residual pressure in the chamber still too high at unlock causing the spent case to be too much pressure bound to the chamber walls at unlock to be pulled cleanly and causing the B/C loose of rearward momentum), or too small (not enough pressure to correctly cycle the action correctly. As for a quick check to see which it is (gas port too small or large), just replace the stock buffer with a H-3 buffer and see if the problem is resolved (or at least bettered). The extra mass of the heaver buffer will slow the action unlock down if in fact the rifle is over cycling. If the heaver buffer does not solve/better the problem, then suspect that the gas port is too small to begin with. Note: you have confirmed that you don't have wicked leaks in the gas system, and that the FSB/gas block is correctly indexed with the barrel gas port? And to add, since you have not given specifics of the rifle, it's configuration, and whom did the SBR'g, all of the above could be totally wrong. |
| The rifle has a H-stamped buffer right now. Is the H3 heavier? Randall at ar15barrels shortened the barrel and supposedly opened up the gas port. How large should the gas port be for a 10.5? matbe I should check that. The front sight base is the factory one that I took off the barrel before sending it in. I there anything you can mess up with the FSB install? |
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Since I don't know the extent of what Randal did for you (if just shortened the barrel and you reinstalled it, or if he worked over the whole top end), I have IM him for some input to this thread. As for the barrel port, it should be somewhere with the .088 to .093 range for a 10.5 barrel, depending if the chamber was reamed Colt SBR (wider in the cross wall dimensions) as well when shortened. |
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