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help!!
does anyone have an idea of why this is happening to me??? the bolt is overriding the round as it tries to feed. it gets partially fed but the bolt is not pushing on the back of the case. i then pull back a little on the charging handle allowing the round to pop up a little then it feeds.
any ideas?? oh and it fails to lock back after the last round
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Sounds like your rifle is under gassed and your bcg isn't coming back far enough to cycle the action properly. Do you have an adjustable gas block?
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Cloverleaf Wrote:Sounds like your rifle is under gassed and your bcg isn't coming back far enough to cycle the action properly. Do you have an adjustable gas block?
Agree
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Better build info will generate better answers. Upper and Lower manufacture, barrel length, buffer weight, magazine used, ammo used, lubrication of bolt, brass ejection direction and distance, markings on fired brass, gas port size, gas block setting, cycling with dummy rounds, etc.
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Another potential problem can be the cartridge head is not seating on the breach face of the bolt because of the ejector. Here is a link to discussion and mod to help improve feeding on some 6.5 Grendel AR-15s. Sounds like your AR-15 might be under gassed but people have experienced failure to feed because of the ejector. It cant hurt to mod the ejector.
http://bulletin.accurateshooter.com/2014...artridges/
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Check your bolt carrier gas key screws. Reverse torque your gas key screws at 30 inch pounds. They should remain tight and not loosen.
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factory ammo or handloads? bullet weight? barrel length? gas system?(rifle, midlength, carbine). as others have said, your BCG isn't being pushed back far enough. this can be caused by several things by themselves or a combination of them. as above. too heavy of a buffer. wrong buffer spring, like a rifle spring in a carbine buffer tube perhaps. under loaded ammo, rare with factory ammo, more of a possibility with reloads. anything causing excessive drag on the BCG, like tons of crud in the action that hasn't been cleaned in ages. a partially plugged gas port or gas tube. a incorrectly adjusted adjustable gas block. shooting way undersized bullets (a handloading oops, which i would think would be obvious, but you never know, like loading 25 caliber bullets in the 6.5 Grendel. i wouldn't think that's possible but......)
-tdbru
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Jonny,
Sounds like a 'Bolt-over' jam.
If your BCG is not travelling fully to the rear and locking back on last round then the the carrier instead ends up trying to feed the round up the ramp = jam.
Solution
- More gas
- Lighter buffer and/or lighter spring
- Both.
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10-03-2020, 02:13 PM
(This post was last modified: 10-03-2020, 02:14 PM by jonny rotton.)
its one of the new group buy 16" barrels in an aero upper with a bcm rail. the bolt carrier is a lightweight nickel boron. bolt is unknown who made it. just a standard spring and buffer. this is not my first build, it may be around my 20th.
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and thank you for all the responses!!!!!!
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i was shooting wolf and hornady sst factory ammo. the sst's may have functioned better than the wolf. i dont remember for sure. i just did the extractor modification.
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I have 450 bushy doing same thing , I know mags can b a big problem . Mine is 16 barrel clgs. I checked and double and triple checked everything is correct ! Except the gas port diam . Mine was .0625 that was the issue , to small ! I enlarged it to .076 problem solved . Just put together a 20 rlgs Grendel this week and a 16 Grendel mlgs. Everything between the grendels is identical except the barrels and gas port . Swapped same lower between the 2 and same BCG. 20 runs great , 16 no so . Im pretty confident its gas port size . Will mic the port tomorrow and see what I find .
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jonny rotton Wrote:help!!
does anyone have an idea of why this is happening to me??? the bolt is overriding the round as it tries to feed. it gets partially fed but the bolt is not pushing on the back of the case. i then pull back a little on the charging handle allowing the round to pop up a little then it feeds.
any ideas?? oh and it fails to lock back after the last round
Classic gas system issue. Often caused by not aligning the gas port with the port on the gas block.
Can also be caused by a loose carrier key that doesnt look loose.
What type of gas block and how tightly is the gas block fit to the barrel?
NRA Basic, Pistol, Rifle, Shotgun, RSO
CCW, CQM, DM, Long Range Rifle Instructor
6.5 Grendel Reloading Handbooks & chamber brushes can be found here:
www.AR15buildbox.com
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the gas key is tight. i will check the alignment and how well it fits when i take it apart today. thank you for the suggestions!!
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the alignment was good. the fit may be slightly on the loose side, its not very tight.
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