Gas Block Problem?

[UncleDano]

Looks like I have a shorter tube in my .308 and the longer tube (from Wilson) in the 6.5 CM. Both are Aero Precision uppers. I can measure the length on the inside of the receiver and the shorter is 7/8" and the longer is 1 1/8". But it appears that the gas key on the BCG is long enough to accommodate both lengths.

 

[ARlife4me]

Looks like I have a shorter tube in my .308 and the longer tube (from Wilson) in the 6.5 CM. Both are Aero Precision uppers. I can measure the length on the inside of the receiver and the shorter is 7/8" and the longer is 1 1/8". But it appears that the gas key on the BCG is long enough to accommodate both lengths.

AP uses dpms gen1. If there is an "X" pattern where the gas tube goes into the upper receiver then it's a dpms. Looks like ar15 uppers.

 

[UncleDano]

AP uses dpms gen1. If there is an "X" pattern where the gas tube goes into the upper receiver then it's a dpms. Looks like ar15 uppers.

Yes, AP is the dmps. Don't know if there is an "X".
Wilson Combat says their rifle tube is 15.125" long.
But they also have a longer one. Here is what is noted on their web-site:

"This 15.5" long, extended stainless steel gas tube is what we use in our large bore AR10 builds. The slightly longer length gives you a better seal with AR10/LR308/SR25 style gas keys for improved reliability and performance."

So, with that information, I would not think that this is a contributing factor to the problem of no bolt lock back on last shot.

 

[ARlife4me]

Yes, AP is the dmps. Don't know if there is an "X".
Wilson Combat says their rifle tube is 15.125" long.
But they also have a longer one. Here is what is noted on their web-site:

"This 15.5" long, extended stainless steel gas tube is what we use in our large bore AR10 builds. The slightly longer length gives you a better seal with AR10/LR308/SR25 style gas keys for improved reliability and performance."

So, with that information, I would not think that this is a contributing factor to the problem of no bolt lock back on last shot.

The X shape is where the gas tube goes into the receiver. With the handguard off you can see it just above the barrel nut. Some gas tubes are straight and some have 1 or 2 bends in it. The bends are to clear the barrel nut and go straighter into the gas key. Those are usually on lowpro gas blocks. The straight tubes are more a2 gas block style or pic rail height gas blocks can be this way also. Not all are equal in design. Measure more in a straight line, but the added bends add length for more dwell time. Measuring the gas tube can be misleading? WC states 15.5" as you stated. Did the gb and gt come as 1 or purchased separately? If separately you might have a slr gas block (very good gas blocks). I have several AP receivers (AR15 and AR10 w/ other AP products), so I'm familiar with them. Site didn't give gas port size. I you have a bore scope, check alignment from inside the barrel. With the spring length being 11" it's a long (by 1.25"), but 25 coils is about right. Flat wire, multi-strand or spiral wound. Length can make a difference when compressed with flat giving a shorter oal compressed. Flat can be longer and have the same amount of coils, because it has more room too compress compared against multi-strand and spiral wound.

 

[cohunt]

Where does the brass eject? 3 o'clock to your right, 5 o'clock, 1 o'clock?

 

[ARlife4me]

Where does the brass eject? 3 o'clock to your right, 5 o'clock, 1 o'clock?

Another good question!

 

[cohunt]

Use this as a guide.
If you are undergassed you need to figure out where your problem is.
Misaligned gas block, partially blocked gas hole, loose gas key, worn gas rings on bolt, gas hole too small. Etc.

 

[lyle2231]

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.

Open up the gas port a little bit. It might take 10 shots to get it adjusted properly. It sounds like the carrier needs more gas to cycle. Have a buddy stand off to the side to observe if your gun's carrier is moving at all. Some times they'll over cycle.
But First I'd try opening up the bleed off screw. HTH!

 

[Okanogan]

It might not be your problem but I have a 224 Valkyrie that I built that failed to catch after the last round. It seemed like the adjustable gas system was working properly and I'd already dialed further open than necessary for function. It had a Seekins part kit in the lower. I swapped out the bolt catch with another one that has a little larger catch shoulder and the problem went away.

 

[skipglo]

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.

I'm with Belldar on this one..different mag. What you could try is loading two or three shells into mag and ejecting them pulling and releasing charging handle. The shells may be pushing the mag down enough so that it won't catch open on last shot. All it would take is probably a 1/16 th of an inch or less to miss! I have had it happen on a polymer clip where it wore down. Just me!

 

[ARlife4me]

Open up the gas port a little bit. It might take 10 shots to get it adjusted properly. It sounds like the carrier needs more gas to cycle. Have a buddy stand off to the side to observe if your gun's carrier is moving at all. Some times they'll over cycle.
But First I'd try opening up the bleed off screw. HTH!

I think he tried it wide open?

 

[ARlife4me]

I'm with Belldar on this one..different mag. What you could try is loading two or three shells into mag and ejecting them pulling and releasing charging handle. The shells may be pushing the mag down enough so that it won't catch open on last shot. All it would take is probably a 1/16 th of an inch or less to miss! I have had it happen on a polymer clip where it wore down. Just me!

He was loading 1 round in mag only for function test. I've had some pmags that wouldn't lrbo properly. Awaiting on more info from @UncleDano.

 

[Hoss Smith]

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.

 

[ntsqd]

I had a Wylde build not work correctly as built some time ago. Research then put me onto Sprinco Springs. Used their selecting method and the recoil spring that they recommended got the rifle performing as it should. I've been using their recoil springs by default ever since.

Built a .308 from extra parts and ordered a Superlative GB for it (one of the very few parts I had to buy). I've been as impressed with it as I have been with the Spinco springs so those too are now a default choice for any non-std build. With a Spinco spring and the Superlative GB I did as the op did, started with the GB turned all of the way down and slowly opened it up until the bolt would lock back. One small step further and I set the locking screw.