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Posted: 12/10/2015 1:40:10 PM EDT
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A friend of mine had built an AR15 on an 80% polymer lower. The hammer pin hole and trigger pin hole were a little too big, the drill had taken a little too much polymer.
During the pre-firing checks it was discovered that the rifle would have fired one round when the trigger was pulled in and then a second round as the trigger was released. It's a good thing my friend thoroughly checked the function before putting live rounds through the rifle! Pulling the trigger in would engage the disconnector but with hammer and trigger too far apart the hammer would not re-engage the trigger, the hammer would have gone forward a second time. With the trigger released, the hammer would finally pick up the trigger and hold, after the second shot, if any shots had been fired. My friend found anti rotation pins, an after market add on that replaces the standard trigger and hammer pins and has a link between the 2 pins. The link forces the correct distance between hammer and trigger pins so that they function correctly. It placed the pins correctly inside the over sized pin holes. The rifle has not yet been fired to confirm it but manual operation of the hammer shows that it now catches the trigger again when the disconnector releases. The anti rotation pins have corrected the hole spacing and returned the correct trigger timing. My friend thanks you for the AR15.com forums, he referenced them many times during the build of his first AR. |
| I have a set of KNS pins on my rifle. Only one pin is threaded on both sides, while the other is longer than the width of the receiver and machined flat on both ends. The dog bones bolt onto the first pin and has slots that fit over the other pin to prevent rotation and walking out. I don't recall them being a tight enough fit to hold them at a fixed and constant distance from eachother. I'm aware of multiple model generations that may use differing attachment methods, but am only familiar with mine and thought it was worth mentioning. Just trying to look out. Good luck and hope it works out. |
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Yes, no, maybe on the KNS pins.
Hence the pin channels for the trigger and roll pins should be in the .154" range, and even if the channels end up being .160", just re-tuning the disco will solve the problem. Worst case, the pin channels get to around .165", and then it time to just ream the channels to .170" for a colt large pin FCG instead. But to step it back up, if the poly receiver is soft to begin with, then the KNS support pins should prevent the channels form enlarging quickly. |
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If the hammer & trigger pin holes in the receiver are oversized, oval in shape, or wallered out, then the KNS pin conversion may or may not work. There is a specific location of where the pins need to be located in order for things to work correctly. If it works then great, if not then you should consider replacing the receiver.
CY6 Greg Sullivan "Sully" SLR15 Rifles TheDefensiveEdge.com (763) 712-0123 |
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