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Posted: 3/12/2015 11:11:05 PM EDT
| I shot some more today through my new AR. I shot 60 rounds through it today making a total of about 140 rounds through the gun. Twice when the magazine was empty after the final shot the bolt did not catch qnd stay open. Instead the bolt closed with no round chambered. What causes this? |
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I shot some more today through my new AR. I shot 60 rounds through it today making a total of about 140 rounds through the gun. Twice when the magazine was empty after the final shot the bolt did not catch qnd stay open. Instead the bolt closed with no round chambered. What causes this? Need more info on rifle. Maker or parts used. |
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Should try other brands of ammo, but my thinking is that the Rem 55 should be okay. Did you try to charge with an empty mag to see if the bolt catch would work?
I had exact same issue years ago with my old Bushmaster, bolt catch failed to arrest the bolt after last shot about 50% of the time no matter what magazine. Ended up changing out the bolt catch to solve the problem (the original one was a few hundredths shorter, probably due to stacking tolerances) |
| It could be that it's not fully cycling, but it could also be cycling too fast. If the gun is overgassed and/or doesn't have enough buffer mass, the bolt carrier velocity can outrun the follower in the mag resulting in the same failure. How is the gun shooting...is it soft with very little felt recoil, or is it kind of violent? How is the ejection...is it mostly towards the 4:00 direction and just barely making it out, or is it more forward and throwing the empties pretty hard? The answers to those questions will determine which direction you need to go in regardless of the make of the gun. I'd recommend starting there before just randomly trying different parts. |
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The gun is a Bushmaster M4A3 w/magpul stuff. <a href="http://s94.photobucket.com/user/ndb8fxe/media/6678B43D-F934-44C0-BA10-5B6007F7C325_zpsirjzm8zq.jpg.html" target="_blank">http://i94.photobucket.com/albums/l81/ndb8fxe/6678B43D-F934-44C0-BA10-5B6007F7C325_zpsirjzm8zq.jpg</a> The magazine is a pmag The Ammo was Remington 55gr. The gun never failed to eject nor failed to chamber, just failed to catch the bolt. Thanks to all who respond, As stated above, run some Lake City M193 (5.56) through it and report back. Don't fiddle with anything, just change the ammo. |
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Sorry, the site wouldn't let me post all of this in one so I had to make several posts:
Okay guys, bear with me as I am new to the Ar15 and certainly appreciate the help. Quoted:
What buffer are you using? Quoted:
What buffer are you using? The buffer is what came with the gun. I'm am unsure of the model/specs. Quoted:
Pay attention to the info given above......the answer to your bolt catch issue has been given. xomyou only have one mag? Try another magazine. Try different ammo. Yes, I only have the one magazine for now. Another 6 are on the way, Magpul windowed. I will be able to experiment when they are delivered. Quoted:
Should try other brands of ammo, but my thinking is that the Rem 55 should be okay. Did you try to charge with an empty mag to see if the bolt catch would work? I had exact same issue years ago with my old Bushmaster, bolt catch failed to arrest the bolt after last shot about 50% of the time no matter what magazine. Ended up changing out the bolt catch to solve the problem (the original one was a few hundredths shorter, probably due to stacking tolerances) Throughout shooting yesterday I did run out of the Remington 223 and had a box of Independence 556 so my last 10 rounds were the 556 and the bolt did not catch after the last round. Good to know about the stock bolt catch. |
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It could be that it's not fully cycling, but it could also be cycling too fast. If the gun is overgassed and/or doesn't have enough buffer mass, the bolt carrier velocity can outrun the follower in the mag resulting in the same failure. How is the gun shooting...is it soft with very little felt recoil, or is it kind of violent? How is the ejection...is it mostly towards the 4:00 direction and just barely making it out, or is it more forward and throwing the empties pretty hard? The answers to those questions will determine which direction you need to go in regardless of the make of the gun. I'd recommend starting there before just randomly trying different parts. I wish I knew how to judge the difference between a soft v violent recoil. I'm new to the species. The range I am at has narrow lanes with partitions, I did not notice the ejection angle. Quoted:
Pull the charging handle back as far as it will go and check to be sure the bolt is in the right place. Use known good ammo like XM193. Do the usual checks for gas leaks, etc. I need to play with it tonight. I haven't had time since leaving the range to mess with it. I'll report back. Quoted:
Did you install your bolt catch plunger correctly? I did not install it. The gun is the way it came out of the box. I did clean and lube it before firing it. For the first 100 rounds I was loading 10 into the magazine at a time and each time the bolt caught after the last round (so the first 10 times, same ammo). I went the next day, and started having the problem. So it worked at first, then started acting up. |
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As stated above, run some Lake City M193 (5.56) through it and report back.
Don't fiddle with anything, just change the ammo. I will try that ammo. I will need to go to a different range. The one closest to home will not allow 5.56, only 223. Thanks to everyone. |
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Quoted: I will try that ammo. I will need to go to a different range. The one closest to home will not allow 5.56, only 223. Thanks to everyone. Quoted: As stated above, run some Lake City M193 (5.56) through it and report back. Don't fiddle with anything, just change the ammo. I will try that ammo. I will need to go to a different range. The one closest to home will not allow 5.56, only 223. Thanks to everyone. Seriously? They let you shoot .223 FMJ, but not 5.56 FMJ? It's basically the same stuff...except the 5.56 may be ~100 FPS faster. |
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Sorry, the site wouldn't let me post all of this in one so I had to make several posts: Okay guys, bear with me as I am new to the Ar15 and certainly appreciate the help. The buffer is what came with the gun. I'm am unsure of the model/specs. Yes, I only have the one magazine for now. Another 6 are on the way, Magpul windowed. I will be able to experiment when they are delivered. Throughout shooting yesterday I did run out of the Remington 223 and had a box of Independence 556 so my last 10 rounds were the 556 and the bolt did not catch after the last round. Good to know about the stock bolt catch. Quoted:
Sorry, the site wouldn't let me post all of this in one so I had to make several posts: Okay guys, bear with me as I am new to the Ar15 and certainly appreciate the help. Quoted:
What buffer are you using? The buffer is what came with the gun. I'm am unsure of the model/specs. Quoted:
Pay attention to the info given above......the answer to your bolt catch issue has been given. xomyou only have one mag? Try another magazine. Try different ammo. Yes, I only have the one magazine for now. Another 6 are on the way, Magpul windowed. I will be able to experiment when they are delivered. Quoted:
Should try other brands of ammo, but my thinking is that the Rem 55 should be okay. Did you try to charge with an empty mag to see if the bolt catch would work? I had exact same issue years ago with my old Bushmaster, bolt catch failed to arrest the bolt after last shot about 50% of the time no matter what magazine. Ended up changing out the bolt catch to solve the problem (the original one was a few hundredths shorter, probably due to stacking tolerances) Throughout shooting yesterday I did run out of the Remington 223 and had a box of Independence 556 so my last 10 rounds were the 556 and the bolt did not catch after the last round. Good to know about the stock bolt catch. Sounds like your over gassed. See what the new mags do, get a couple different kinds of brand ammo, it may just need an H or H2 buffer. |
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Sounds like your over gassed. See what the new mags do, get a couple different kinds of brand ammo, it may just need an H or H2 buffer. Quoted:
Quoted:
Sorry, the site wouldn't let me post all of this in one so I had to make several posts: Okay guys, bear with me as I am new to the Ar15 and certainly appreciate the help. Quoted:
What buffer are you using? The buffer is what came with the gun. I'm am unsure of the model/specs. Quoted:
Pay attention to the info given above......the answer to your bolt catch issue has been given. xomyou only have one mag? Try another magazine. Try different ammo. Yes, I only have the one magazine for now. Another 6 are on the way, Magpul windowed. I will be able to experiment when they are delivered. Quoted:
Should try other brands of ammo, but my thinking is that the Rem 55 should be okay. Did you try to charge with an empty mag to see if the bolt catch would work? I had exact same issue years ago with my old Bushmaster, bolt catch failed to arrest the bolt after last shot about 50% of the time no matter what magazine. Ended up changing out the bolt catch to solve the problem (the original one was a few hundredths shorter, probably due to stacking tolerances) Throughout shooting yesterday I did run out of the Remington 223 and had a box of Independence 556 so my last 10 rounds were the 556 and the bolt did not catch after the last round. Good to know about the stock bolt catch. Sounds like your over gassed. See what the new mags do, get a couple different kinds of brand ammo, it may just need an H or H2 buffer. It would more likely be undergassed than overgassed. My 11.5 is absurdly overgassed with the suppressor and H buffer (to the point that the brass goes of the front of the port and falls about an inch or two from the rifle) but it still locks back. I tend to think that it may be a faulty catch. Make sure you are getting strong ejection to the 3-4 oclock area. Bolt catches aren't expensive so 
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It would more likely be undergassed than overgassed. My 11.5 is absurdly overgassed with the suppressor and H buffer (to the point that the brass goes of the front of the port and falls about an inch or two from the rifle) but it still locks back. I tend to think that it may be a faulty catch. Make sure you are getting strong ejection to the 3-4 oclock area. Bolt catches aren't expensive so
I only say that because OP said it locks back fine on 223 but when he ran out he used 5.56 and it didn't lock back. Good point about the bolt catch. |
| Clear the rifle. Lock in empty mag. Use the charging handle to draw back the bolt all the way and let it go forward until the bolt catch stops it. This will show you that either you have a magazine/bolt catch problem or a recoil problem where the bolt carrier retracts far enough to pick up a round out of the magazine but not far enough to trip the bolt catch. This would either be insufficient gas (from ammo or gas port/tube) or a problem in the buffer tube, like a spring too strong or the buffer bottoming out. |
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Seriously? They let you shoot .223 FMJ, but not 5.56 FMJ?
It's basically the same stuff...except the 5.56 may be ~100 FPS faster. Seriously? They let you shoot .223 FMJ, but not 5.56 FMJ?
It's basically the same stuff...except the 5.56 may be ~100 FPS faster. Yup, that's what the guy there said. I only say that because OP said it locks back fine on 223 but when he ran out he used 5.56 and it didn't lock back. Good point about the bolt catch. Actually, I better clarify. The bolt catch failed using both types of ammo, the Rem 223 and Indy 556. The first day I shot the gun(about 80rnds of 223) the bolt catch did not fail. I was loading 10 rounds each time so it worked fine for the first 8 magazines. The next day I was doing the same thing, but 5 rounds at a time in the magazine. The bolt catch worked a few times, then failed a couple times on the 223. I ran out of the 223 so I shot 10 rounds of 556 and the bolt catch still failed. Quoted:
Clear the rifle. Lock in empty mag. Use the charging handle to draw back the bolt all the way and let it go forward until the bolt catch stops it. This will show you that either you have a magazine/bolt catch problem or a recoil problem where the bolt carrier retracts far enough to pick up a round out of the magazine but not far enough to trip the bolt catch. This would either be insufficient gas (from ammo or gas port/tube) or a problem in the buffer tube, like a spring too strong or the buffer bottoming out. I plan on doing this right when I get home, I'll report back. Thanks everyone! This site rocks! |
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So I finally got to mess with it a little tonight. Here's what I figured out:
With the magazine empty, I pulled the charging handle back numerous times. The first few times the bolt did not lock back, then the next few times the bolt did lock back. After some experimentation I figured out that if there was slight forward pressure on the magazine the bolt wouldn't catch. If I wiggled the magazine then the bolt would start catching. My new magazines should be here tomorrow so I will be interested in seeing if it does this with the new ones. |
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Alright, my new magazines came in today. The bolt catch does the same thing, slight forward pressure on the bottom of the magazine and the bolt catch fails, but slight aft pressure and it catches. Any thoughts? What brand are your new magazines? I have had excellent results with NHMTG, Brownell's and D&H magazines. C-Products are cheaply made. ASC is the new company making those. I have never tried Lancer. |
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Poorly manufactured/out-of-spec/unaligned gas port or block. Quoted:
Poorly manufactured/out-of-spec/unaligned gas port or block. Even though it is happening when pulling the charging handle? Quoted:
What brand are your new magazines? I have had excellent results with NHMTG, Brownell's and D&H magazines. C-Products are cheaply made. ASC is the new company making those. I have never tried Lancer. They are magpul pmag moe w/window. |
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Even though it is happening when pulling the charging handle? They are magpul pmag moe w/window. Quoted:
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Poorly manufactured/out-of-spec/unaligned gas port or block. Even though it is happening when pulling the charging handle? Quoted:
What brand are your new magazines? I have had excellent results with NHMTG, Brownell's and D&H magazines. C-Products are cheaply made. ASC is the new company making those. I have never tried Lancer. They are magpul pmag moe w/window. I didnt see the memo that this happens when you pull back the CH as well. Something is out of spec. Can you take pics of the bolt catch area of your lower? |
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