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glivdub03

issues that cant be solved

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Hoping I could get some answers/help on my ar15 that I built a year ago and still cant get it to shoot without a malfunction. So here is the list of parts i used for the build.

 

Spikes lower with daniels defense parts kit.

 

R guns upper chamber 5.56 16 inch barrell

 

bushmaster stock with carbine buffer spring and heavy buffer

 

mags that i use are p mags 10rd

 

ammo xm193 62g and 55g 5.56

 

The lower was put together by a close friend who has done several ar builds. The upper was already assembled when i bought it. I lubed the gun with a good amount of m-pro 7 oil and was ready for the range! The issue i am having is when you fire the first round it ejects but when it trys to pick up a second round the bolt comes forward, the face of the bolt catches the case at the neck and while the bullet is in the feed ramp.So what happens the case is crushed at the neck.To clear it i have to drop the mag and pull back the charging handle give it a smack and it falls out.I had the gun inspected at a local gun shop and feed ramps smoothed out. The gun shop i brought it to checked the gas system, cleaned and oiled it, smoothed the feedramps, inspected the lower along with other parts. They said the lower was put together correctly and to go test fire it to see if the issue is solved. It is still doing the same thing and i dont know what to do. Any help would be very appreciated.. Thanks

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the simple solution is process of elimination...

 

try your lower on someone elses upper..

your upper on another lower..

different magazines..

 

 

one you figure out which one is causing the issue.. pinpointing the issue should be much easier..

the feed ramp should not have to be "smoothed"

I had a similar issue and it was a magazine related issue..

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I thought there was a issue with the feed ramp so i had him polish it. None of my friends shoot, the only one that does is in afghanistan and i wont see him for a while. I was going to do what you said with trying another ar and swap parts to see what the issue is. Also I have tried pro mags,pmags, 30rd mags and they all do the same.

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I had a similar issue also and it was a cheap thermold mag.

 

Do you shoot at the bullet hole? If you do I should be there with my AR this morning, when they open.

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When an AR runs perfectly (like it's supposed to) it's a ballet in motion.

When sh*t happens and things don't work, it's like the 9 year old daughter's dance class on a bad day.

 

Sounds like a timing issue to me.

The buffer and buffer spring must coordinate the dance with the gas system exerting forces in the opposite direction, while the mag (spring, follower and feed lips) present a fresh round at just the right time and place to get slammed home into the waiting chamber.

 

I'd look at the buffer area (buffer and spring) first.

I'm not a licensed gunsmith, nor did I stay at a Holiday Inn Express last night, but it is new years!

Good luck and I'm curious what solves your issue.

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As others said, could be a mag or buffer/spring problem. Could also be a gas system problem, like a blockage in the front block. I'm assuming it is a carbine gas length system? Are you running a standard carbine weight buffer, or one of the special heavier models?

 

Check the buffer/spring travel inside the tube. Make sure its not getting caught up on anything, like a dimple in the tube or something.

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I have had this rifle apart on the bench........

 

All seems normal....I broke the entire rifle down and rebuilt it ensuring all parts were assembled to common specifications....

 

There did not appear to be any obstruction in the gas system, the front sight gas block was/is attached properly...the rear stock was removed as it was not on properly, but has been corrected.

 

All operations on the bench appear normal. We did NOT test fire the rifle after re-assembly. However the OP noted to us that the same problem persists...

 

We recommended to change mags first (seems that was done to no corrective effect), we also recommended to change the tube/spring/buffer assembley.

 

NOTE the rear stock WAS pinned and I did NOT check that piece to see if it was providing an obstruction to operation...my bad....

 

I can and will meet you at CR this week and we can swap uppers and lowers on a known working carbine for further investigation

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My money is on the mag. Is it a 10/20 PMAG? The follower in those mags tilts when the spring is compressed when limiting capacity which is why all my blocks are internal to the spring to maintain factory spring rates.

 

*ETA: Hmm...I missed his post saying he's tried different mags.

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My money is on the mag. Is it a 10/20 PMAG? The follower in those mags tilts when the spring is compressed when limiting capacity which is why all my blocks are internal to the spring to maintain factory spring rates.

 

*ETA: Hmm...I missed his post saying he's tried different mags.

 

It is..........

 

I TRULY believe it is in the Buffer/spring/tube.... I does not appear visually or bench mechanically anything else....

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- Check the gas key screws for tightness.

- Try a different buffer spring

- Try a lighter buffer. If you are handy, you can actually drive out the roll pin and remove the nylon end piece, then you can easily add/subtract weight.

- What diameter is the gas hole in the barrel? It should be around 0.065-0.085" or so

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First off thank you for all your replys, The mags i have are as following. 10 rd steel pro mag, 15rd/20rd pin pmag, also tried it with 30 rd p mags that a friend used in afghanistan. I have a heavy buffer in the gun now that i bought from BCM and i have the original bushmaster buffer that came with the butt stock as well. I removed the buffer spring and measured it, 10 3/4 inches long. I believe that is close to the minimum length but i could be wrong. Thanks again for all the help everyone! You guys are great!

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When you took the spring out, did the spring get caught on anything other than the retaining pin that holds the buffer in? It sounds like either a lack of gas, or the BCG isn't traveling all the way back (possible roll pin obstructing the spring/buffer). Take it out again and look into the tube and make sure its clear. Also, put the lighter buffer in and see what happens.

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When you took the spring out, did the spring get caught on anything other than the retaining pin that holds the buffer in? It sounds like either a lack of gas, or the BCG isn't traveling all the way back (possible roll pin obstructing the spring/buffer). Take it out again and look into the tube and make sure its clear. Also, put the lighter buffer in and see what happens.

 

When I removed the buffer spring i had to help it out but it was never stuck in the stock. my next day off i will install the lighter buffer to see what happens.

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When you took the spring out, did the spring get caught on anything other than the retaining pin that holds the buffer in? It sounds like either a lack of gas, or the BCG isn't traveling all the way back (possible roll pin obstructing the spring/buffer). Take it out again and look into the tube and make sure its clear. Also, put the lighter buffer in and see what happens.

 

Doesn't sound like lack of gas to me. At least not a serious lack of gas. with a full on short stroke situation, you tend to not get a second round feeding. If anything it sounds overgassed. THe bolt is coming back fast enough that the round hasn't fully risen up in the magazine, and it's contacting the case wall rather than getting behind the case rim.

 

Usually that means either a) your follower is dragging on something in the mag, your feed lips aren't right, or your mag springs aren't right. or b) that you are overgassed, slamming the BCG back real fast and having it ram forward real fast and outrunning the operation of a perfectly functional magazine.

 

To glivdub03 and Nickjc, I'd recommend getting it together with both a known functional carbine length lower and a known working rifle length lower. You also might try swapping the bolt carrier (not bolts though) between a known working upper and the problem child. It could just be the carrier binding up due to dimensional issues with the upper (never even heard of that, but anything is possible), or interfering with the buffer retainer pin.

 

Could also jsut be that everything is fine except the gas port is oversized.

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I have the same exact thing happen with my gun. Where did you get your pmags? I ordered mine from riflegear and they worked great for years but recently the second to the last round has been giving me the same problem. I switched to a heavy h2 buffer from bcm and it seems to be working better. I also degreased the gun and frog lubed it which really smoothed out the action. I would first try other mags then if this does not work try what I did it seemed to help. Also check to make sure your o rings on you bolt carrier group are holding a good seal. Do this by taking out the bolt and leave it forward then set it boltface down on a table and see if the bolt goes in. I hope you get it up and running

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Nickjc and I went to the range this afternoon to try and solve my ar15 issue. We swapped parts around and came to the conclusion that it is a ammo and mag problem. I am buying a new buffer spring and mags then i will go from there. I guess the two mags i have are no good.

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I have had this rifle apart on the bench........

 

All seems normal....I broke the entire rifle down and rebuilt it ensuring all parts were assembled to common specifications....

 

There did not appear to be any obstruction in the gas system, the front sight gas block was/is attached properly...the rear stock was removed as it was not on properly, but has been corrected.

 

All operations on the bench appear normal. We did NOT test fire the rifle after re-assembly. However the OP noted to us that the same problem persists...

 

We recommended to change mags first (seems that was done to no corrective effect), we also recommended to change the tube/spring/buffer assembley.

 

NOTE the rear stock WAS pinned and I did NOT check that piece to see if it was providing an obstruction to operation...my bad....

 

I can and will meet you at CR this week and we can swap uppers and lowers on a known working carbine for further investigation

the stock is the factory bushmaster fixed unit from my wife's ar...i gave it to Travis. it worked perfect, i replaced it with a BCM kit and MOE stock that was all the way in because my wife is short and it was too long.

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It was installed crooked and the nut was buggered...I removed it...checked.it...replaced the nut tghted accordingly and made sure it was straight etc.....dunno if this made a difference but I do.believe it was a combo of.mags and ammo

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any ammo suggestions? I want to try another ammo type besides federal, Also do the pinned p mags have weaker springs in them because of the 15 rd cap? Thanks again for the help Nick, It was fun shooting that mauser.

 

Depends on how they were limited. I've seen some that have a compressed spring and they usually have feeding issues. If the mags you're using were made by me, the block is inside the spring and you have the same spring rate and behavior as a regular, un-limited PMAG straight from Magpul.

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