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#1720439 - 01/28/21 05:43 PM AR15 Build Help
MD0772 Offline
Single barrel

Registered: 01/07/21
Posts: 35
Loc: Virginia
City or County: virginia beach
So I decided to build my own 5.56 Ar15, ordered the parts I needed and after they came in I sat down and put it all together every thing looked good.. at least I thought so went to the range to test it out and it would fire one round eject the round but not reload.. did all the safety checks and reloaded and fired same result repeated several time but got the same result. So I decided to take the BCG out of my other AR and put it in the new build and just like that every thing fired correctly. So I decided to put the new BCG into my old AR to see if it would firer and everything worked as it should .. so I put the BCG back into the the original weapons they came out of and went to firer the new build with the original BCG it had in in and it would firer once eject round but not reload…

Can any one give me any ideas on this seams out there to me any help greatly appreciated

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#1720507 - 01/28/21 08:12 PM Re: AR15 Build Help [Re: MD0772]
ChrisC Offline
Gun fool

Registered: 08/19/12
Posts: 758
Loc: Prince William County
City or County: Nokesville
Are the bolt carrier groups identical? If one is slightly heavier, it may be the additional inertia that you need to cycle completely. Not sure if you are using a standard spring and weight, but I would check those to make sure it’s not an H2 or H3 buffer. Or replicate the bolt carrier group that works, and make sure it’s lubed well.

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#1720566 - 01/28/21 10:08 PM Re: AR15 Build Help [Re: MD0772]
RASAT Offline
Pea shooter

Registered: 10/28/19
Posts: 15
Loc: VA
City or County: Fairfax
I'm not absolutely sure but I suggest you to Check and compare the Buffer, 2H works very good for AR Carbine 5.56, Regards

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#1720582 - 01/28/21 11:19 PM Re: AR15 Build Help [Re: RASAT]
ChrisC Offline
Gun fool

Registered: 08/19/12
Posts: 758
Loc: Prince William County
City or County: Nokesville
Originally Posted By: RASAT
I'm not absolutely sure but I suggest you to Check and compare the Buffer, 2H works very good for AR Carbine 5.56, Regards


Usually, but with one BCG functional and the other not it’s worth checking. I suspect it’s under gassed and the alignment of the port and gas block should be checked, now that I’m thinking about it. That one BCG may be just a bit different in weight and overcoming it.

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#1720619 - 01/29/21 06:23 AM Re: AR15 Build Help [Re: MD0772]
Verylargeboots Offline
Professional FUDD Hater

Registered: 10/10/16
Posts: 728
Loc: VA
City or County: Lynchburg
Did you check the headspace? Lol
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#1721025 - 01/29/21 09:42 PM Re: AR15 Build Help [Re: MD0772]
MD0772 Offline
Single barrel

Registered: 01/07/21
Posts: 35
Loc: Virginia
City or County: virginia beach
I will check these things out and get back to you all thanks for the help and suggestions

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#1722374 - 02/01/21 06:46 PM Re: AR15 Build Help [Re: Verylargeboots]
Bcmgunfighter Offline
Not all ARs are created equal...

Registered: 12/20/12
Posts: 3365
Loc: Virginia
City or County: Rochelle
Originally Posted By: Verylargeboots
Did you check the headspace? Lol


I was wondering this as well.
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#1728245 - 02/13/21 06:43 PM Re: AR15 Build Help [Re: MD0772]
ak66 Offline
Sharp Shooter

Registered: 06/20/17
Posts: 2301
Loc: VA
City or County: Fairfax
Headspace would be a suspect. On AR-15s it’s highly rare but can happen. Tell us more about the BCGs. Are they both standard full-auto M16 cut and the same weight/type? If both are identical from reputable manufacturers, check your buffer spring and weight - swap buffer and weight from your other AR and put it in new one. If still having issues - check gas block alignment, if it’s adjustable open it completely, if still fails check buffer tube extension (make sure it’s properly seated and staked).


Edited by ak66 (02/13/21 06:45 PM)
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#1728551 - 02/14/21 01:40 PM Re: AR15 Build Help [Re: MD0772]
nvcdl Offline
Bullseye

Registered: 04/03/13
Posts: 1991
Loc: ORANGE
City or County: Orange
I'd suspect the new build has marginal gas and the finish of the swapped in BCG is slicker from wear/worn enough to make it work. I'd check alignment of the gas block as another poster suggested.


Edited by nvcdl (02/14/21 01:42 PM)

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#1728829 - 02/14/21 11:08 PM Re: AR15 Build Help [Re: MD0772]
siklonelinyx Offline
Siklone Linyx

Registered: 01/05/21
Posts: 395
Loc: Hampton Roads
City or County: Hampton Roads
Are the new rounds getting stuck where the feed ramps are? What type of rounds are you using? Steel or brass. If steel, your upper may not like it and have to test it with brass. If the your bcg isn't the problem since you tested out your new and old ones and they performed well, that may be the cause of the issue. Manually cycle your rounds. When the rounds gets ejected, are there any scratches on the actual bullet?
Edit: Just saw the og post date, not sure if you've fixed the issue or not.


Edited by siklonelinyx (02/14/21 11:09 PM)
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#1729798 - 02/16/21 08:51 PM Re: AR15 Build Help [Re: MD0772]
2nd.amend Offline
Shooting blanks at Magnum force! ;)

Registered: 12/20/12
Posts: 3966
Loc: Gainesville va
City or County: Gainesville
If you put the spring on the hammer wrong it can do this !
But not sure why it only dose with the one bolt may be a gas block problem

Switch the lowers that would eliminate the hammer spring


Edited by 2nd.amend (02/16/21 08:52 PM)
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#1730589 - 02/18/21 01:47 PM Re: AR15 Build Help [Re: MD0772]
jims59 Offline
Gun fool

Registered: 05/09/11
Posts: 1122
Loc: Virginia, USA
City or County: Manassas
I had a problem with my AR, It was doing the same thing. I took a mop that fit the chamber, put it on a drill and added a little Fitz to polish the chamber and it has run great ever since.

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#1762400 - 05/09/21 12:06 PM Re: AR15 Build Help [Re: MD0772]
shootergdv Offline
Marksman

Registered: 07/08/10
Posts: 317
Loc: VA
City or County: Rustburg
Short stroking ? For grins , leave the bolt in place, swap the spring and buffer . If it works , compare the spring and buffer .
Just maybe one spring is slightly longer/stiffer -or buffer is different. The difference in weight of semi-full carriers as stated above could certainly work against you too .If so, the redneck fix would be to snip a coil.

You'll figure it out ! Part of the fun of DIY .

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