Posted: 9/20/2010 6:20:48 PM EDT
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First off I did do a topic search for this issue, but didn't find anything that matched.
I have a DPMS AR-15 Carbine with an A2 upper reciever and 11.5" barrel with a pinned 4.5" flash hider. The rifle has worked great up until last Sunday at the range. When I squeezed the trigger the round would go off, the bolt would cycle throwing the spent shell out and picking up a new one from the magazine and then lock back into the barrel. Went for my second shot and the trigger never reset. I racked another round in the chamber and squeezed the trigger. The same thing happed again, it fired off the round, ejected the spent one, loaded a new round but didn't reset the trigger. When I looked at the live rounds that I ejected from the chamber I noticed that the fire pin had tapped the primer but didn't set it off. The rounds weren't duds, because a was able to fire them off by resetting the trigger by hand. The rifle has less than 200 rounds through it and everything is new from DPMS. I used anti-walking pins on the trigger set so I know thats not the problem. So I'm at a lose as to what could cause a "slamfire" without the fire or the trigger to not reset. Any help or ideas on were else to look would be great. Thank You for your time. Chuck. |
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The dimple on the primer was from the firing pin hitting the primer when it slammed closed on the chamber, and is normal.
Remove the upper, and hold your thumb so you can stop the hammer from slamming on the lower when you pull the trigger. Pull the trigger (keep it pulled back) which should release the hammer. Now reset the hammer like the bolt would. When the hammer is all the way back, the hammer should be held by the disconnector. Now release the trigger - the hammer should move forward about 1/8" when the disconnector releases it, and the sear on the trigger catches it. Did this happen properly? Short stroking possibly - was this the first time you shot this ammo? |
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Quoted:
The dimple on the primer was from the firing pin hitting the primer when it slammed closed on the chamber, and is normal. Remove the upper, and hold your thumb so you can stop the hammer from slamming on the lower when you pull the trigger. Pull the trigger (keep it pulled back) which should release the hammer. Now reset the hammer like the bolt would. When the hammer is all the way back, the hammer should be held by the disconnector. Now release the trigger - the hammer should move forward about 1/8" when the disconnector releases it, and the sear on the trigger catches it. Did this happen properly? Short stroking possibly - was this the first time you shot this ammo? As above, but restated: do a proper function check of the trigger group. If this is correct then put one round in the mag, load it via the charging handle, and see if the bolt locks back. If the bolt doesn't lock back, you may have a short stroke issue, which can be due to many things. Also, the gunsmithing forum under Armory is the best place to take this if you want to work out the issue yourself rather than sending it back...shame on you for bringing guns into GD 
ETA: if the gun fails the function check, first make sure all the fire control group parts are installed correctly. Especially make sure that all springs are installed correctly. |
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Quoted:
The dimple on the primer was from the firing pin hitting the primer when it slammed closed on the chamber, and is normal. Remove the upper, and hold your thumb so you can stop the hammer from slamming on the lower when you pull the trigger. Pull the trigger (keep it pulled back) which should release the hammer. Now reset the hammer like the bolt would. When the hammer is all the way back, the hammer should be held by the disconnector. Now release the trigger - the hammer should move forward about 1/8" when the disconnector releases it, and the sear on the trigger catches it. Did this happen properly? Short stroking possibly - was this the first time you shot this ammo? I preformed the above test and found out the Disconnector is not grabbing the trigger at all. It seems to be loose for some reason. The disconnector on my CAV lower is tight and does have any lateral movement like the DPMS lower does. |
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Quoted:
Quoted:
The dimple on the primer was from the firing pin hitting the primer when it slammed closed on the chamber, and is normal. Remove the upper, and hold your thumb so you can stop the hammer from slamming on the lower when you pull the trigger. Pull the trigger (keep it pulled back) which should release the hammer. Now reset the hammer like the bolt would. When the hammer is all the way back, the hammer should be held by the disconnector. Now release the trigger - the hammer should move forward about 1/8" when the disconnector releases it, and the sear on the trigger catches it. Did this happen properly? Short stroking possibly - was this the first time you shot this ammo? As above, but restated: do a proper function check of the trigger group. If this is correct then put one round in the mag, load it via the charging handle, and see if the bolt locks back. If the bolt doesn't lock back, you may have a short stroke issue, which can be due to many things. Also, the gunsmithing forum under Armory is the best place to take this if you want to work out the issue yourself rather than sending it back...shame on you for bringing guns into GD
ETA: if the gun fails the function check, first make sure all the fire control group parts are installed correctly. Especially make sure that all springs are installed correctly. Sorry for the GD post, Newbie mistake. I put this lower together and it has functioned well in the past. I guess I'll be pulling it apart. |
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