Troubleshooting help - Bolt not locking back on empty mag.

[WoobieJ]

New build, see specs below.

Despite several adjustments, I'm not able to get the gun to lock back on an empty mag. The gun functions well aside from this, especially with the standard (white) spring and 2.2oz buffer (smoothest recoil impulse with reliability between ammo).
Interventions so far -
- replaced 4.4 oz PWS buffer and spring with spring co white (standard) and standard carbine buffer then,
- KAK buffer @ 2.2oz then
- 1.7oz then
- 1.7oz + springco yellow (reduced power)
- Then after taking the law tactical folding stock adapter and buffer tube down, I found that the PWS (not law tactical compliant version) buffer tube was sent with the lower, and changed it to the law tactical compliant buffer tube, and I have yet to see if this has resolved the issue.
- I also checked the gas block and tube, there is no obstruction or malalignment of the gas tube to gas port as seen below, and an unremarkable amount of gas leakage around the block.
- The gun is effectively lubricated.
- I am using 20 round gen 3 PMAGs
- the bolt catch spring looks to be the correct spring with normal strength

If replacing the buffer tube with the compliant version does not resolve the issue,
- what about the bolt catch/release?
- I will attempt to run the gun with a normal bcg
- I will attempt to run the gun on a pws lower that doesn’t have a law tactical folding stock adapter that is otherwise identical

Any other trouble shooting insight would be appreciated.

Upper
Bootleg Upper Reciever
Bootleg 15” rail
Bootleg low pro gas block .750
Melonited rifle length gas tube
Bootleg Adjustable BCG (Unsuppressed, •, •, Suppressed)
Proof Research .223 Wylde 18” SS Barrel (1:8, 0.750”, Rifle Gas)
BCM gunfighter Charging Handle

Lower
PWS Mod 2 lower
PWS Buffer tube and Ratchet endplate / nut
Geissele LPK
Noveske ambi 60 degree safety
Larue MBT Trigger
Law Tactical Folding stock adapter
LMT DMR 5.56 Stock

Buffers and springs I have -
KAK adjustable buffer kit (1.7oz, 2.2, 2.6, 3.0, 3.8, 4.3, 4.7, 5.6oz)
SpringCo Yellow reduced power buffer spring
SpringCo White Standard power buffer spring
PWS buffer spring (looks to be slightly heavier and a few more coils than standard)
PWS 4.4 Oz buffer

 

[davsco]

interested in advice also. my recent build works every other time. i adjust the position of the gas block and lock it down. shoot it no problems, pick it up the next day and it goes back to not loading the next round.

 

[The DFC]

Tried different/different types of mags with same results?

 

[clcustom1911]

No need to answer my questions. Just putting them out there for you to marinate over...

Gas rings on your bolt staggered (gaps not lined up)?
Does the bolt catch freely move with just the retaining pin installed? May need some fitting.
How old are the PMag springs? May not have enough force to push bolt catch up.

I would run everything with standard parts, i.e. standard BCG, Buffer, springs, etc and see if that resolves the issue.

I only work with non-folding stocks, so as far as issues the extra folding length may cause, I'll defer to someone with more experience.

 

[Constructor]

If you have a leak at the gas block/barrel or gas tube/gas block seal the leaks with blue Loctite. The pressure is apx 12000psi, a little leak can cause problems.

 

[bfoosh006]

I also think your GB is leaking more then I would want.

How many rounds through it ?

It is leaking front and rear.. the barrel shoulder has gunk on it.

And if you got the GB off without scratching some of the gunk off... I would wonder about diameters.


And given the light buffer weights.. are you sure it isn't out running the various other parts ?

IE, the cyclic speed ( BCG ) is going faster then the bolt catch / mag spring can keep up with.

 

[WoobieJ]

No need to answer my questions. Just putting them out there for you to marinate over...

Gas rings on your bolt staggered (gaps not lined up)?
Does the bolt catch freely move with just the retaining pin installed? May need some fitting.
How old are the PMag springs? May not have enough force to push bolt catch up.

I would run everything with standard parts, i.e. standard BCG, Buffer, springs, etc and see if that resolves the issue.

I only work with non-folding stocks, so as far as issues the extra folding length may cause, I'll defer to someone with more experience.

I’ll answer for other’s brainstorming as well

1. I’ll check gas rings
2. It runs freely but does have some resistance. I was wondering if it should have friction against trigger?
3. New pmags. Have not tried other than new 20 rounders
4. I’ll do that

Thanks!

 

[WoobieJ]

I also think your GB is leaking more then I would want.

How many rounds through it ?

It is leaking front and rear.. the barrel shoulder has gunk on it.

And if you got the GB off without scratching some of the gunk off... I would wonder about diameters.


And given the light buffer weights.. are you sure it isn't out running the various other parts ?

IE, the cyclic speed ( BCG ) is going faster then the bolt catch / mag spring can keep up with.

Yea I was wondering if it was an acceptable amount or not. Ill loctite it and see.
The gun was under gassed day 1 with the 4.4 Oz buffer and spring and standard carbine buffer and spring, that’s why I kept going down in weight and spring strength.

 

[WoobieJ]

Probably 200 ~ rounds though it so far all different types of ammo

 

[WoobieJ]

What about permatex or rocksett on the GB? Or just stick with blue loctite?

 

[Constructor]

Not silicone. Permatex 1 or 2 gasket maker or blue Loctite is what we have been using since the late 80s.

 

[hlee]

That looks like a shit ton of gas blow by on your barrel. I've got a 6.5 Grendel with about 500 rounds through it. If I can remember to, I'll pull the hand guard off and take a pic of the gas block- it's never been cleaned. My uninformed opinion is that your gun is woefully undergassed because your gas block doesn't fit and is allowing way too much gas out of the system...

 

[clcustom1911]

That looks like a shit ton of gas blow by on your barrel. I've got a 6.5 Grendel with about 500 rounds through it. If I can remember to, I'll pull the hand guard off and take a pic of the gas block- it's never been cleaned. My uninformed opinion is that your gun is woefully undergassed because your gas block doesn't fit and is allowing way too much gas out of the system...

Yeah, looking closer at the gas journal area, that's A LOT of carbon build-up. The gas block will leak a little during the first 50-100 rounds, but it should still function fine and dandy.

 

[WoobieJ]

Ok guys I’ll get it fixed and see if that solves the issue. Any more suggestions on things to check are welcome

 

[hlee]

Here are 2 different rifles, both in 6.5 Grendel. The left is an Odin works 18" mid length gas barrel with a no name non adjustable gas block. I haven't kept track of the round count, but it has more than 100 through it. This is the first time since I put it together that the hand guard has been off. No observable gas leakage.

The rifle on the right is a 22" JP barrel with a SLR adjustable gas block. It is obvious that I'm getting some leakage from the djustment screw, but there is no leakage around the block-barrel junction. This rifle has around 500 rounds through it...

 

[WoobieJ]

I haven't sealed up the gas block yet, I'm just wondering if it will seal itself up if it already has this much carbon after 200 rounds?