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Posted: 5/9/2011 1:56:08 PM EDT
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Hi Everyone,
I just completed an AR15 build, but I have one nagging problem that I'm not sure how to solve: the bolt catch is not catching the face of the bolt. This holds true when firing or when pulling the charging handle with an empty magazine installed. After doing some reading, I gave a closer look at the bolt catch assembly. The magazines *are* catching the bolt catch properly, and I do have the correct spring installed in the catch. This doesn't seem to be the issue. However, when I slide the bolt carrier group back with the charging handle it reaches the maximum extent of its travel about 1/16" before the bolt catch. The bolt face can't travel back far enough for the catch to engage. I attempted to isolate the problem: First, I removed the buffer and buffer spring and verified that without these installed, the bolt carrier can travel back as far as necessary. No problem. I repeated this exercise with the buffer installed in the buffer tube, but no spring. When the buffer is in place, the bolt carrier can NOT travel back far enough to allow the bolt catch to engage. Adding the spring does not make the issue worse. The parts involved are: CMMG 16" Mid-length upper (included BCG) Advanced Technology Receiver Extension Buffer Tube Assembly (Part # 657408 from Midway) Stag Stripper Lower DD Lower Parts Kit. When the gun is fired, it works fine with the exception of bolt catch on empty magazine. Ejection is good and I had no failure to fire or feed problems in running ~ 80 rounds through it. It seems like the buffer is ever so slightly too long (or the tube is ever so slightly too short) and preventing full travel from the BCG. Not so much so as to create firing problems, but enough to prevent the bolt catch from working. Something is obviously not quite right, but I don't know what part I should look to replace/return. Advice? Thanks! |
| That that I was going to say... Make sure your buffer is going all the way back in the tube.... Frist remove the spring and buffer and check how back the carrier is going back It should be close to 14 inch from the bolt catch.. then install the buffer with out the spring and test it again and see if its moving to far foward.... I had to cut about a 1/8 of an inch off my buffer pad in order to get my sons to cycle back enough for the bolt catch it grab it... Moreso if your using a Twang buster....or any spring cusion on the back of your spring.... Most peps dont use these things..... |
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I found this thread while doing some additional digging for answers:
http://www.thehighroad.org/showthread.php?t=589462 It seemed similar enough that I pursued it further. The depth of my buffer tube measured the same as the author of the above thread: 6-13/16" He didn't say what brand of buffer tube he had, but it looks an awful lot like the one I have and seems to have the exact same problem. Most of the information I've seen on the depth of carbine length tubes indicates that it should be 7". The additional 3/16" would be enough to allow my bolt carrier to travel back far enough for the catch to engage. I dropped a note to ATI (buffer tube mfg) to see if they think it is a manufacturing flaw. Hopefully they'll respond and send me a new tube. I don't want to have to buy another tube if theirs is under-depth. |
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Quoted:
I found this thread while doing some additional digging for answers: http://www.thehighroad.org/showthread.php?t=589462 It seemed similar enough that I pursued it further. The depth of my buffer tube measured the same as the author of the above thread: 6-13/16" He didn't say what brand of buffer tube he had, but it looks an awful lot like the one I have and seems to have the exact same problem. Most of the information I've seen on the depth of carbine length tubes indicates that it should be 7". The additional 3/16" would be enough to allow my bolt carrier to travel back far enough for the catch to engage. I dropped a note to ATI (buffer tube mfg) to see if they think it is a manufacturing flaw. Hopefully they'll respond and send me a new tube. I don't want to have to buy another tube if theirs is under-depth. You are about the 5th or 6th person I have heard that has had this same issue with ATI tubes ... they seem to have a real quality control problem. 
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| Actually I had the problem with a Tapco buffer and stock assembly I really don't know who makes it for them but it as 1/4 to short for a carbine rifle but its good to check as I described above. A funny thing I found out is they sell the separate rubber bumper on the back of the buffer. But I also found my Spikes SP-22 buffer had a little smaller pad so I got a couple from them in case I run into this again... I think the problem is they leave to much material on the back side (inside) of the buffer tube... I did inform Tapco when I came across this since I had purchased two of the kits from them and one went on an AK with an adapter so the spring and buffer was not needed but on my sons AR-15 it caused me some problems in figuring it out... |
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Update:
ATI has been very responsive and helpful. They agreed that it sounded like a depth problem. They're sending me a shipping label and will send me a new tube once mine is returned. I'll update the thread again once everything gets straightened out. It seems to me that they might have had a "run" of short-drilled tubes and will probably be taking steps to remedy the situation. Fortunately, they seem fairly committed to making it right, so I'm not too worried or upset about it –– apart from being without my AR for a while. |
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ATI verified that the buffer tube was one a group that slipped by QC, but was milled slightly too shallow. I should have my new tube on Monday.
I'm happy with the way ATI handled this. They've been responsive and helpful, which I greatly appreciate. Sure, I wish the tube hadn't slipped by QC, but all things considered, it worked out. |
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