Select fire, upper will only run on normal gas setting

[whoreticulture]

10.5 LWRC upper, Suppressed with an H3.

It will only select fire reliably if in Normal gas mode, S mode I get LPS or fail to fire hammer dropped. S mode is so much nicer recoil impulse though, Is there anything I can do to get it working on S mode reliably without removing the can?

Isnt S mode made for cans and increase reliability?

[99cobra2881]

Whats the firing pin protrusion? Min. 028”-.035” Max. Try an H2 buffer?

What did LWRC say when you called or emailed them?

[Bret]

That's confusing. Light primer strike or fail to fire hammer dropped would indicate bolt carrier bounce. In S mode the rifle should be getting less gas which should mean that carrier bounce is less likely. I'm interested to see what the solution is.

[markm]

The fact that something from LWRC will run at all is a miracle. Buy a lottery ticket.

[Clint]

Check for empty mag lock back in semi on setting S.

Possible issue with the auto sear?

[JoshNC]

If you’re saying that on the suppressed setting it won’t run without a can, that’s the whole point. To Clint’s point, the autosear adds drag on the carrier, which is moving at lower velocity on suppressed setting without the can. A light primer strike occurs on essentially all chambered ammunition in an AR that lacks a firing pin spring. The dead hammer on a live round sounds like bolt bounce, but that doesn’t make a whole lot of sense in this scenario. It’s worth a call to LWRCI.

[whoreticulture]

All shots fired with a can, I will not be using this upper without one. Too much blast.



N mode functions as should on Semi/Select/ bolt lock on last round ect.

S mode does not function reliably with select, but works and locks bolt on semi with last round.

Lower is using a Maxim Defense PDW with a H3 4.85oz


This upper does work on S mode in Select with a standard Milspec buffer tube and Spikes T3 installed. I just prefer the shorter PDW if we can figure out how to remedy this.

[Bret]

The Spikes T3 is shown as being a 5.4oz buffer. I still suspect carrier bounce, but honestly don't know anything about the Maxim Defense PDW. Just curious why you're running a brace on a machinegun.

[whoreticulture]

Extremely long day testing it, different buffers & springs & cans. She will not run more than 4-5 round bursts in S mode with any combination of buffers springs or cans. Switch to N and its flawless even mag lock on last round.

Since Maxim only makes an H3 (4.85oz) is there a way to modify it heavier or dare I try the JP silent capture spring?

[MistWolf]

What gas system does your upper have? I mean, is it what they call a piston system? Or is it direct gas?