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Did a couple of modifications: polished the chamber using 1500 wet-dry lubed with WD-40 wrapped around a lapping tool and then finished off with a .410 shotgun swab coated in Semichrome polish with the cleaning rod chucked up in a drill motor. The fired cases look really nice now, no scuffs, nothing. Polished a slight radius on the sharp edge on the ejector and put a radius/bevel on the inside. This allows the case to pivot to the right when ejecting, same as you do to a fixed ejector on a 1911pistol or FAL rifle, etc. A lot of AR guys swear by this and it did improve the ejection plus the ejector was digging into the case head with a nasty smear streak and it no longer does that, just rubs through the lacquer coating on the Wolf ammo now. The cycling feels so good now. I was getting stovepipe jams about every 5 rounds and forward ejection, today I fired 80 rounds and it ran like a sewing machine! Every detail thing helped it function better but reducing the gas port from .094" to .063" made most of the difference.
![[Image: NKiDMPq.jpg?1]](http://i.imgur.com/NKiDMPq.jpg?1)
Empty cases ejected about 8-9' perfectly at 3:00 and piled up in a beautiful pile about 3' across. Wolf 100 gr. 6.5 Grendel ammo. Nice!
![[Image: NJQ7Jfs.jpg?1]](http://i.imgur.com/NJQ7Jfs.jpg?1)
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I added a Sprinco extra power buffer spring and an H buffer. Both made the gun cycle smoother and better. Up to 140 rounds now and not a single malfunction.
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DeanD Wrote:I added a Sprinco extra power buffer spring and an H buffer. Both made the gun cycle smoother and better. Up to 140 rounds now and not a single malfunction.
Very nice write up and pics on how you fixed the over gassing problem. Have you shot any ammo besides the Wolf yet? Id like to know how the barrel shoots with better quality ammo? Thanks.
peak98
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Excellent thread really. That was a great fix for the oversized gas port.
I knew you had plenty of gas since you were getting Last Round Bolt Hold Open every time, but stovepipes and 1 o'clock ejection.
You can also tune the corners of your extractor lip and it will baby brass more, without any chance to impinge the case rims during ejection articulation from the bolt face recess.
I do that on my builds if they don't have a precision ground edge on the extractors.
Keep an eye on the chromed bolt, as that is usually a recipe for hydrogen embrittlement and stress risers at the lug roots and cam pin hole.
If fed a diet of Wolf, it should last longer though since projectiles are smaller diameter and charge weights aren't very high.
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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I am up to 165 rounds now without a single malfunction of any type since reducing the gas port. No more stovepipe jams, no faulty ejection, nothing. Just runs like a sewing machine! Even though it worked well with the .063" gas port I added an H buffer and a Sprinco extra power buffer spring and both made it cycle even smoother and more consistent.
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Check out the last part of this video comparing ejection patterns between 6.5 Grendel and 223. My own high speed videos are similar to these.
http://www.brassfetcher.com/Rifles/6.5mm...endel.html
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tried to post a video, didn't work
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06-14-2020, 02:52 PM
(This post was last modified: 06-14-2020, 03:04 PM by VASCAR2.)
Dean I have a cousin to your J&T 16 6.5 Grendel that is over gassed. My 16 6.5 Grendel is the heavy profile CMV barrel with Phantom flash hider I bought it as a complete upper from J&T. I went a different route to solve my over gas issue. I bought a 12 Group Buy Green Mountain 1:7.5 twist barrel where I wanted to assemble an upper. Since I already had a Monster bolt I needed a bolt carrier. I decided to buy a Rubber City Armory adjustable gas key and a new stripped M-16 phosphate carrier, FP, FP retainer and cam pin. I moved the J&T bolt, cam pin, FP with retainer to the new bolt carrier with RCA adjustable gas key. I used my J&T carrier with my new 12 Monster barrel build.
The RCA adjustable key took care of my J&Ts gas issue as it now ejects brass to 3-4 O Clock. Even Wolf steel case was ejected at 2 O clock without adjusting the gas on the J&T. I was using an H2 buffer with the J&T upper so I just left it in there and adjusted the gas. This has really improved the functioning of this 6.5 Grendel. I never measured my gas port on my 16 CMV barrel but it never lacked for gas! This J&T barrel shoots really well and Im glad I decided to try the RCA adjustable carrier.
