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Posted: 4/17/2008 3:28:46 AM EDT
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I have a M16A1 lower and a Noveske upper. I can fire semi, no problems. I can dump a full mag, no problems. However, when I fire bursts (2, 5, 10 rounds) I will, at times, have a FTF. The round chambers fine and when manually extracted has a small dent in the primer. Any ideas guys? Thanks |
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Need to check auto sear release gap, and confirm that you have at least a H-3 buffer to control the stoke if the lower is a carbine unit with such upper. For timing, with the rifle empty and the selector set on full/burst, tape the trigger back and while riding the Charging handle all the way back then forward, insert the back end of a drill bit through the front of the ejection port between the face of the bolt and the face of the barrel extension. With a drill bit sized at .090 or greater, the hammer should not be released from the sear with the drill bit blocking the front face of the carrier from reaching the face of the barrel extension. With a drill bit sized at .080 at the same point, the hammer should be released, hence the ideal release gap should be .083, and anything greater than this is an advanced release gap. On the buffer, it has to not only control the stroke/unlock, but also act like a dead blow hammer as well, or the carrier will bounce back and the FP will be blocked by the back of the carrier when the hammer goes to strike it. With too light of a buffer in a carbine lower, the buffer will sling shot off the back of the receiver extension (read lack any rear dead bolt effect here), which cause even a greater problem on the forward dead blow effect ( read leads to increased bolt bounce on lock up). P.S. Welcome to the site!!! |
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