Gas Block Problem?

[blvette75]

I have the same upper with the Aero precision barrel on it used a Seekins adjustable gas block on mine to resolve my issue. My Creedmoor was over gassed, I believe I would start with the mag, as mine always locked if I provided enough gas to it. Then Wilson, my brother had the same problem on a .308 he went with a non-adjustable block and that remediated his issue. On mine I had to use the adjustment to make it more consistent to shoot. It still beats up my brass though. I also went with all silencer recoil spring assembly, I think that is what called, maybe that piece doesn't make difference, but part of my project.

 

[Hirschi1]

Buffer weight? To heavy, or to light?

 

[UncleDano]

Okay guys, here is what I discovered at the range today:

I took a closer look at the empty cases (all of them, not just one) and what I noticed was a progression of light cratering to more severe cratering and the last two rounds showing cratering with pierced primers. So this shows a progressive increase in gas pressure, which makes sense as I progressively adjusted it upwards. So I cranked the gas block down to the lowest setting (xsn10s=score one point). Switched to a new 20 round mag (belldar=score one point), loaded it with 3 rounds instead of one to check for short stroking (ARlife4me=score points). Fired first two rounds; no failure to feed etc., but third (last shot) did not lock bolt open. Opened up GB two more clicks, and success, bolt stayed open on last round. Let my buddy shoot as I watched, and noticed brass ejects @ 3:00 o'clock - perfect!

Functioned properly there after, except for one instance of failure to lock open when just one round loaded in mag.. So I am thinking that Magpul PMAG M3 is maybe not the best choice for this 6.5 CM build. So situation is much better, but not perfect. Maybe a little experimentation with buffers as suggested might get me to perfect. On second thought, is there such a thing as a perfectly functioning M5? Thanks guys!

So in summery, I made some real rookie mistakes.
1. I Used a brand new Pmag, never tested for function. The follower did not return fully to top of lips.
2. instead of starting with 2 or 3 rounds in mag to test for short stroking first, I just put in one round to test for lock back.
3. When lock back did not happen, I assumed gas was set too low, instead of trying a tested known functioning Pmag.
4. I continued to ratchet up the gas until it was maxed out and over-gassing and probably bouncing the bolt back into battery.
5. Failed to think my way through it logically. And start over.

 

[cohunt]

Try asc sr25 stainless mags or Lancer mags (poly with ss lips)

The lips can be tweaked if needed to help feed angles-- the asc mags allow longer loading (coal) than the poly mags do also.

Glad you figured it out

 

[UncleDano]

That buffer is a lot on the too light side, for a 6.5Creedmoor AR! An adjustable gas block helps, but you need a heavier buffer. In mine, I'm running 3 tungsten weights, just to get it running properly. My 6.5 Creedmoor AR10, has an occasional primer piercing issue, from it being a high pressure cartridge and Palmeto State Armory, not replacing the original gen 1 bcg, with their new, high pressure bcg assembly...still torqued off about that, but the rifle is a legitimate half inch rifle out to a 1000!

What was total weight of buffer you settled on?

 

[lyle2231]

I never knew the breakaway existed before? I use a bore scope.

Should you need to: HB Industrie ; 6448 S. Ash Ave; Tempe 85283

 

[UncleDano]

I have the same upper with the Aero precision barrel on it used a Seekins adjustable gas block on mine to resolve my issue. My Creedmoor was over gassed, I believe I would start with the mag, as mine always locked if I provided enough gas to it. Then Wilson, my brother had the same problem on a .308 he went with a non-adjustable block and that remediated his issue. On mine I had to use the adjustment to make it more consistent to shoot. It still beats up my brass though. I also went with all silencer recoil spring assembly, I think that is what called, maybe that piece doesn't make difference, but part of my project.

What is your brass looking like?
Mine seems to be denting the case mouth quite consistently.

 

[kfreeze]

As other have said, try another mag first just to be sure. Preferably a different brand mag.

After that, call wilson. It sounds like you may need your gas port opened up a little bit. Also tell them that you are using an adjustable gas block. When I order barrels from x-caliber and tell them that, they open up the gas an extra .010" to give more reload options for me.

Also, if you happen to need any mags for dpms pattern ar10, I have a bunch of dpms factory mags that are for sale.

 

[smokey3]

Pulling back on charging handle does lock it open. Not sure that LOWERING the gas would help. Will try different ammo when I can find it.
Waiting to hear back from Wilson Combat.

Try a lower pressure spring because it sounds like it is not pushing the bolt back far enough to lock open

 

[ARlife4me]

Okay guys, here is what I discovered at he range today:

I took a closer look at the empty cases (all of them, not just one) and what I noticed was a progression of light cratering to more severe cratering and the last two rounds showing cratering with pierced primers. So this shows a progressive increase in gas pressure, which makes sense as I progressively adjusted it upwards. So I cranked the gas block down to the lowest setting (xsn10s=score one point). Switched to a new 20 round mag (belldar=score one point), loaded it with 3 rounds instead of one to check for short stroking (ARlife4me=score points). Fired first two rounds; no failure to feed etc., but third (last shot) did not lock bolt open. Opened up GB two more clicks, and success, bolt stayed open on last round. Let my buddy shoot as I watched, and noticed brass ejects @ 3:00 o'clock - perfect!

Functioned properly there after, except for one instance of failure to lock open when just one round loaded in mag.. So I am thinking that Magpul PMAG M3 is maybe not the best choice for this 6.5 CM build. So situation is much better, but not perfect. Maybe a little experimentation with buffers as suggested might get me to perfect. On second thought, is there such a thing as a perfectly functioning M5? Thanks guys!

So in summery, I made some real rookie mistakes.
1. I Used a brand new Pmag, never tested for function. The follower did not return fully to top of lips.
2. instead of starting with 2 or 3 rounds in mag to test for short stroking first, I just put in one round to test for lock back.
3. When lock back did not happen, I assumed gas was set too low, instead of trying a tested known functioning Pmag.
4. I continued to ratchet up the gas until it was maxed out and over-gassing and probably bouncing the bolt back into battery.
5. Failed to think my way through it logically. And start over.

I've used g2 and G3 mags for 6.5creed without an adjustable gb, but with AP barrel w/standard rifle length system. Functioned perfectly with Hornady 123 amax and sst. No over pressure issues or bolt hold open on last round issues. Carbine spring and standard buffer weight and never missed. With other brand barrels with same ammo all had would pop primers. Loading 3 rounds at least is where I start before tuning gb. 260rem is closer to a 308win case and feeds better than the 6.5 does. 243win in an AR is more troublesome too run. Glad you're back and running smooth!

 

[Wisco 308 fan]

There is no standard on AR-10 parts and there are at least two different rifle length gas tube lengths. You may have a standard length gas tube that just barely makes it's way into the gas tube receiver on top of the bolt carrier and need the longer one it's about 1/4" longer if memory serves me. I would call the barrel manufacturer and ask what length gas tube is required for their barrel.

Absolutely spot on. I just built an AR10 and had to get a .25 longer gas tube. The cycling was ok up a point but would not lock back. I changed the tube and it's been running great since then.

 

[Wisco 308 fan]

What is your brass looking like?
Mine seems to be denting the case mouth quite consistently.

I'd suggest that you look at the brass deflector like in the picture. I've put a few on and it has helped with denting the case mouth...just a suggestion

 

[lyle2231]

I had same issue with a 6.5 Creedmoor. A gunsmith with a lot of real world experience with a multitude of AR platforms recognized my gas block was not exactly aligned with the port in the barrel. A different guns it's, who had been and done what this young man had, recommended drilling out the gas port. Once he got the gas port aligned, works perfectly.

Okay guys, here is what I discovered at the range today:

I took a closer look at the empty cases (all of them, not just one) and what I noticed was a progression of light cratering to more severe cratering and the last two rounds showing cratering with pierced primers. So this shows a progressive increase in gas pressure, which makes sense as I progressively adjusted it upwards. So I cranked the gas block down to the lowest setting (xsn10s=score one point). Switched to a new 20 round mag (belldar=score one point), loaded it with 3 rounds instead of one to check for short stroking (ARlife4me=score points). Fired first two rounds; no failure to feed etc., but third (last shot) did not lock bolt open. Opened up GB two more clicks, and success, bolt stayed open on last round. Let my buddy shoot as I watched, and noticed brass ejects @ 3:00 o'clock - perfect!

Functioned properly there after, except for one instance of failure to lock open when just one round loaded in mag.. So I am thinking that Magpul PMAG M3 is maybe not the best choice for this 6.5 CM build. So situation is much better, but not perfect. Maybe a little experimentation with buffers as suggested might get me to perfect. On second thought, is there such a thing as a perfectly functioning M5? Thanks guys!

So in summery, I made some real rookie mistakes.
1. I Used a brand new Pmag, never tested for function. The follower did not return fully to top of lips.
2. instead of starting with 2 or 3 rounds in mag to test for short stroking first, I just put in one round to test for lock back.
3. When lock back did not happen, I assumed gas was set too low, instead of trying a tested known functioning Pmag.
4. I continued to ratchet up the gas until it was maxed out and over-gassing and probably bouncing the bolt back into battery.
5. Failed to think my way through it logically. And start over.

Happy to hear that you got it working! Thanks for the analysis.

 

[jasonco]

What was total weight of buffer you settled on?

6.41oz total rifle buffer and I did switch to a Luth AR MBA-1 rifle length buffer assembly, for the extra weight.