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Posted: 2/28/2004 11:30:43 AM EDT
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I have a brand new Colt SP1 that I recently registered as an SBR. I took it out to fire today. I tried two different uppers and had the same problem with both. First, sometimes but not always I would have 2-4 shots fired with each trigger pull. There are absolutely no FA parts in the gun. It would then fail to fully extract the last shell. I think that the carrier is not traveling back far enough. Important info: Car stock Colt SP1 lower small hole adaptor pin for large hole lower 7.5 inch upper and 11.5 inch upper carrier and upper lubed after problem started but problem was not fixed Problem started after about 15 rounds At the beginning the buffer retaining pin and retaining pin spring came out. I tightened the car stock and it has not come out since. Any help would be appreciated. Thank you. |
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Lock the carrier back, then hold the trigger and tag the bolt release. Chances are that the disconnector is letting the hammer loose as the carrier slams shut. If this is the problem, then you will need to check the FCG to see if something is worn, or if the FCG is a small pin set, installed in the Colt large pin receiver, with the slop in the parts causing the problem. The other thing to check is to hold the trigger back, charge the weapon (not loaded), then very slowly release the trigger. The hammer should be released from the disconnector, and then retained by the trigger sear. If the trigger slips past the trigger sear, then again, check out the FCG for worn parts, or if the correct pin size FCG is installed. |
| I don't think that the problem is mismatched parts. It is a "new" rifle. Everything appears to be where it should be. I tried the function check and it worked as it should. All parts are unused and should not be worn. The hammer was locked back and released to the second lock point when I let go of the trigger. I think the slamfire is because the carrier did not move far enough back to lock back the hammer. I lubed everything up (especially the buffer and spring) and tried again. This time the first 5 shots when well and then the short stroking started, but no slam firing. I noticed that the bolt retainer seemed especially prominent. I wonder if the carrier is rubbing against it on the way back and not moving the whole way back. I am going to try and compare the position of the bolt catch with that of another lower. Any other suggestions? Both uppers had the EXACT same problems, I am guessing the problem must be in the lower. Thank you. |
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Quoted: I think the slamfire is because the carrier did not move far enough back to lock back the hammer. If the bolt moved far enough back to pick up a new round, then the carrier lowered the hammer past the disconnector hook, which is unless you have a 9mm colt hammer in a 223 rifle. Everything appears to be where it should be This is a scary statement!!! Either the FCG is installed correctly, with the correct parts, or it's not. If nothing else, find someone that can check out the install of the lower parts, and the uppers to the lower if you are using offset bushing. My guess is that the disconnector is releasing/slipping the hammer before bolt locks closed, and what you think is short stroking is in fact the hammer catching the firing pin on the forward stroke (the built in safety device if the disconnector has a problem). Short stroking means that the carrier never went far enough back to eject the spent round, lock the bolt back after the last round, or has the ability to strip a new round out of the mag. In short, lets get the lower up to speed, then we can attack the problems with the SBR uppers (the 7.5" is going to be a bitch to get it to run right, no matter what lower you have it on) |
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The rear of the hammer may also be contacting the top rear of the disconnector hard enough to keep it from grabbing the hammer on the hammer's forward stroke. This can be checked with a no mar. Start with the trigger held to the rear and the hammer cocked onto the disco. Firmly strike a glancing blow to the face of hammer with the no mar. Repeat several times. The hammer should not fall. ETA, this isn't one of the Colt's that use the funky discos is it? |
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