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Posted: 1/6/2009 1:20:10 PM EDT
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Hi, folks. I know didly squat about the internal workings of an AR, so I hope you folks can point me in the right direction. I build 1911s, so if you can give me the right road, I'm pretty sure I'll be able to understand what you tell me to do.
I have a Bushy shorty upper on a pre-ban Colt Delta lower. The problem I'm having is that the bolt only goes about 1/2 way to battery (looking through the port, you can see the bolt stopped about half way down the length of the port. This happens now every time when the gun is being fired (good ammo - Federal GMM), and it happens every third or fourt time when the gun is empty and I hit the bolt release to drop the bolt closed from lock. Would appreciate some help with diagnosis and remedy. Best, Jon |
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If the gas tube is correctly aligned with the key,
The check two other areas, The first is the upper receiver just below the feed ramps. If the bullet is low feeding, the tip will be tagging the upper receiver there (denting). Next, if you have an un-shrouded carrier, then you need to check the collar of the FP to confirm that it's not protruding above the carrier ramp, and even checking the hammer if it's a semi L cut model (read hammer catching the firing pin collar on the forward stroke). Reducing the FP collar OD so it sits just below the top of the carrier ramp when seated against the back of the carrier, and even breaking/stoning the L cut edge on the top of the hammer's firing pin contact pad will resolve the hammer catching the FP collar on the forward stoke. |
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Hi, guys. I think some wires are crossed in our conversation, and part of it's my fault.
This is not going to be a gas-system problem because this even occurs when I'm firing the rifle AND when I DRY fire it. Let me explain the sequence of events better than I did: During Live Fire: 1. Fire rifle. 2. Bolt goes back and eject the emptyy. 3. Bolt starts back forward, starts another round out of the mag, but then stops half way to battery. (I am still holding trigger back at this time.) I had thought it might just be a feeding issue UNTIL . . . During Dry Fire: 1. Rifle unloaded, in battery, and cocked. 2. Pull the trigger, and the rifle dry-fires. 3. Without releasing the trigger, grab the charging handle, fully retract the bolt, and then let it go forward. 4. Without releasing the trigger, start allowing the bolt to go back forward. 5. Bolt goes half way home but stops half way to battery. 6. Release the charging handle. 7. Release the trigger. Bolt staysy put. 8. Grab the charging handle again and slightly retract the bolt. 9. Bolt now free to go all the way home. Would appreciate any guidance you could give me on what's wrong. Best, Jon |
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Do your dry fire test one more time, and when the B/C sticks about half way forward, see if you can close the bolt with the forward assist only.
If you can close the bolt with the FA, you have binding going on, such as the top of the hammer to the bottom of the carrier slot sides, buffer bumper roll pin to spring, spring wind bur to the tube it's self, or even the cam too tight in the upper track. If the FA will not close the bolt, then the hammer has caught the firing pin collar, or the gas tube did not enter the key correctly. |
| I'm no expert, but.. since the rifle will cock when the trigger is NOT held to the rear, it sounds like the disconnnector is not holding the hammer. The hammer is riding the bolt carrier forward and is catching on the firing pin. The hammer WILL reset when the trigger is at rest because the disconnector does not come into play here. Check to see if there is a disconnector/disconnector spring in place and the large end of the disconnector spring goes down into the trigger. Also make sure the tail of the hammer is not wedging against the disconnector. |
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Forward asssit will not close the bolt when the rifle is locked up. One must retract the bolt slightly using the charging handle to get things to free up.
Not sure I follow about the disco thing. The rifle will cock when the bolt is retracted by hand or by firing, regardless of whether the trigger is held back or not. Seems to me that's normal operation. Also, once the trigger is released, the disco does what it should and resets so that the trigger then can be pulled to trip the sear (fire the gun). At least it works that way on a 1911, so it seems like the same general principles would apply here. After running it through my brain awhile, I'll bet that the hammer is, in fact, hangin' up on the FP collar. There's no FP shroud, by the way. I'll break it back down tonight and see what I find. Thanks again, guys! Best, Jon |
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Just reporting back that this was an easy fix. Finally got around to tearing the AR down this morning. Discovered there was no disco spring in the gun! Made one up from some spring stock, and good to go (at least dry firing okay.) From what I can tell, the hammer was being pushed back far enough to cock, but without the disco spring there to get the hammer to lcok on the sear, the hammer followed but then tog stuck on the bolt carrier before it went all the way into battery (thank goodness!)
Best, Jon |
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