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Posted: 7/6/2005 6:55:33 PM EDT
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I'm still learning, so excuse me if this topic has been addressed before. I was shooting my Bushmaster AR this weekend (has had >1000 rounds in its life), and I noticed something that struck me as odd. I had the bolt open, and I set the rifle down, butt first, to lean it against a wall. When the butt of the rifle struck the ground, the bolt closed as if I had intended to chamber a round. I didn't slam the rifle on the ground by any means. Perhaps a little harder than usual, but nothing that would come anywhere close to abuse. Is this normal? If so, why does this happen? I can't think of any reason this would be good or bad, but I just wanted to make sure my rifle is functioning properly. Thanks for the help. Nick |
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The problem you describe has never happened to me, but I can venture a guess as to what happened. When the rifle hit the ground the inertia of the bolt carrier compressed the buffer spring in the stock just a little. This extra travel of the bolt carrier released the bolt catch and allowed it to snap back to its normal position which allowed the buffer spring to send the bolt home. You may want to look at the bolt catch to see if it's damaged. Have you ever had the bolt go home after the last round in a mag? It's also possible that you might want to get a new buffer spring. Just my .02 -yj |
I was thinking the same thing, actually. I've never had any problem with the bolt staying shut after the last round. I'm looking at the bolt catch right now, and it appears to be in full working order. I'm clueless on this one...does this give me an excuse to order the VLTOR stock and Mil-spec buffer I've been wanting? Hahaha. |
Ok, so that's one thing that doesn't make sense here - this AR has somewhere in the neighborhood of 800 rounds through her, total. I purchased her brand new in mid-2004, and haven't given her the attention she deserves. |
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Interesting new development: The bolt will close when the mag well is empty, or when I have one of my aftermarket 30 rounders in (make unknown), but not when I insert the factory Bushmaster 10 round mag. Thoughts? Edit: Now I'm really confused. It was closing earlier with a loaded 30 rounder, but now it will only close when I have no mag in the mag well. Ugh... |
You need to explain this a little more. ETA Is the problem with loaded or unloaded mags? -yj |
It is with loaded mags, and with an empty mag well. If I have an empty mag in the well, and tap the butt, it stays open. |
I have no idea what kind of mags they are, to be honest. They were given to me as a birthday gift, and have no markings on the floorplate of the mag. They were brand new as of May 1, and have seen maybe 400 rounds of use. |
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#1 how clean is the lower? Is there any debris preventing the bolt catch from freedom of movement? Clean with a good blast of Gun Scrubber brush and lube with CLP. If you have to, take it apart and see if there is an obstruction. Next examine the Bolt Carrier and see if it is damaged or rounded out to much at the bottom of the forward bolt area where the contact is made. If worn it could be slipping over the catch. If you manually depress the bolt catch when the bolt is open, and then ease the bolt closed until it catches will it stay? If the rifle gets banged under this situation will the B/C close? If all that is ok then the next step is to look at your mags. Are they clean? Take them apart and look at the internals. How loose are they when in the magwell? You can tighten the mag catch by using a round and pushing the mag release until you can spin the catch itself. Clockwise to tighten it up a bit. Just one turn then test, repeat if necessary. The follower inside the mag is the part of the mag that will push up the bolt catch to lock the B/C open after the last round. Look closely at the contact area of the followers to see if there is wear, they might not be pushing the B/C up far enough to maintain a solid lock on the B/C. If the followers look good then I would get new springs for the mags. What color are your followers? Does this situation happen with all, some, or one mag? |
It is with loaded mags #1 The bolt is supposed to close on a loaded mag to load the next round. Normal an with an empty magwell. #2 the bolt will close on a empty magwell because there is nothing to push up on the bolt catch to hold the bolt open. Normal if I have an empty mag in the well, and tap the butt, it stays open. #3 The empty mag in the magwell will hold the bolt catch up in place. The mag spring is stronger than the bolt catch spring. Normal If you remove the mag from the magwell on an open bolt the mag can no longer put pressure on the bolt catch. If you were to tap the rifle in this state the bolt will drop back relieving enough pressure to allowing the spring loaded bolt catch to retract allowing the bolt to close. Normal |
The lower is clean. I shot it a bit earlier today, but it doesn't have any debris or other gunk that would cause the bolt catch not to function properly.
There is no damage or rounding of the bolt carrier that I can see. If there was any damage, it would have been done by the factory...1000 rounds shouldn't be enough to cause visible wear, should it? When I depress the bolt catch with the bolt open, everything seems to be normal. If I want it to stay open, it stays open. If I want to close the bolt, it will close. If I insert an empty mag and pull the charging handle, it will stay open just like it should. The only time the bolt closes due to impact is when I have no mag in the mag well, or when I have a loaded mag in the mag well, in which case, it will chamber the round.
The mags are all clean. There is a little bit of play when I wiggle the mag back and forth. I tightened the mag release as tight as it will go (can't get past the bolt release any more), and I can see the threading of the screw on the mag release button. It may have helped a little bit, but I'm not sure if it was necessary. Thoughts? The follower in the Bushy mag is green, and in the 30 rounders it is black. There doesn't appear to be any real wear on any of the followers. This happens with all the mags when loaded, no matter what capacity or brand. |
Damn you, Rollyman! Couldn't you have told me something was messed up with my buffer tube so I'd be forced to go out and buy a new stock and tube?  Thanks, mate! I'm glad all is well with my girl! She shoots like a champ, and looks just as good! 
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I think your answer has already been posted. The inertia of your bolt compressed slightly against the recoil spring, just enough to release the bolt hold open, thus releasing the bolt to move forward (on a loaded mag or empty magwell, an empty mag will continue to engage the bolt hold open.) This is normal, just varies on how hard you have to "set it down" between makers and the recoil springs they use. Perhaps your spring was never as strong as others, or your broken it in well already. In my opinion, it's not a good idea to insert a loaded magazine into a rifle with its bolt open and set it on the ground. Go ahead and close the bolt on the mag, or BEFORE the mag is inserted, depending on what condition you want to have your rifle in. ALWAYS engage the safety FIRST, before loading the rifle (unless you're ready to shoot.) |
You know on second thought maybe there is a problem with your buffer and spring. I think you should go get a VLTOR stock and buffer set up and do a function check. Just to make sure.  That is if you need someone to give you a reason. |
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