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Posted: 3/25/2009 2:45:40 PM EDT
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I got the urge to build an AR just before the election. Thanks to this forum it's been a great experience. However, I have a problem I can't solve. The carbine has a High Standard lower, Armalite middie upper and Stag LPK. So Far so good. I decided to put a CAA CBS stock on the rear. I think the receiver tube that came with the stock was too short because the bolt catch would not always engage. It appeared the bolt would not travel far enough to the rear. I replaced the CAA unit with a milspec tube, spring and buffer, added a Magpul CRT and now I believe the bolt travels too far to the rear. Never had a problem going bang but now even though the bolt stays open on the last shot I noticed the brass is nicked on the rim and the bolt will travel to the end of the opening or a tad past. Is there a mechanism to shim the tube for travel?
Thanks in advance. |
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If you are looking for a specific part you may want to ask in the discussion forum. It sounds like you aren't looking to troubleshoot.
For the record it doesn't sound to me like you have a problem with carrier travel. Quoted:
I decided to put a CAA CBS stock on the rear. I think the receiver tube that came with the stock was too short because the bolt catch would not always engage. It appeared the bolt would not travel far enough to the rear. Sounds like a spring issue? (barring you don't have some crazy buffer selection, gas issues, lack of lube) I replaced the CAA unit with a milspec tube, spring and buffer, added a Magpul CTR and now I believe the bolt (I assume you mean bolt carrier?) travels too far to the rear. Why? Because the BCG rides the buffer until the buffer reaches the end of the receiver extension when you hand cycle it? Never had a problem going bang but now even though the bolt stays open on the last shot I noticed the brass is nicked on the rim (how nicked?) and the bolt will travel to the end of the opening or a tad past. (Okay? Sounds right.) Is there a mechanism to shim the tube for travel? I'm not sure of the exact sizes, but there are different (polyurethane?) bumpers you can put on the end of your buffer. Also, I've heard of using quarters in the end of the buffer tube. I'm not sure I would go that route though. Thanks in advance. You may have a different experience with different ammo. Good luck, and try to post some pics of your cases if you can. |
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There are two lengths of receiver extension,
Standard A-1/A-2, then the shorter telescoping carbine length. With these, there are standard length buffers for the longer receiver, and the shorter buffer for the carbine stock (telescoping). As for springs, again two lengths, with the standard 11.75" long, and the carbine at 10.5" long. Note: the A1 and A-2 receivers extensions are one and the same, with the A-2 set up using an end of tube spacer and the butt stock screw 5/8" longer to create the 5/8" longer LOP than the A-1 stock. Bottom line is the specific receiver extension requires the specific buffer and spring, and if something is wrong and you have the correct parts in play, the suspect that the depth void of the tube is out of spec (defective product that needs to be returned for replacement). |
| Thanks all. I've been trying to get my head around this all day. You guys are right My problem is not with the distance the bolt carrier travels, It's timing. That being said, is the way to change the timing with the buffer spring or the weight of the buffer? BTW the nicks on the brass are on the face of the rim. They are 180 degrees apart and are not deep or gouged by any means. more like shiny smudges. Ammo is Q3131. |
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Shiny smudges are called "bolt swipe" and yes timing can be adjusted with a spring and or buffer. Call some of the custom builders and they should be able to coach you on what to buy from them
to cure it or call Armalite and get their recommendation on the right spring and buffer. |
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