Gunsmithing Custom adapter for AR-style stock

[BurnOut]

I have lately been looking at various (bolt gun) chassis that offer an interface for an AR-style "buffer" tube and therefore AR-compatible stocks. However, I like folding stocks for a variety of reasons, and while there are a variety of folding adapters for AR-style buffer tubes (i.e., https://xlrindustries.com/collections/accessories/products/push-button-folding-adapter), I cannot find one that has any sort of locking/retention in the open position.

However, Sig offers one that does (https://www.sigsauer.com/store/sig-sauer-stock-adapter-1913-interface-folding-knuckle.html). The hitch is that it doesn't attach to the chassis via the typical buffer tube-style threads, as the Sig MPX and MCX guns have a short bit of vertically-oriented pic rail on the ass end of them. So, I'm looking for someone to make a custom adapter that threads into a chassis as would an AR-style buffer tube, but can have a short bit of pic rail bolted on to accommodate the Sig adapter. I'd think that it would be relatively quick work for anyone with a lathe and a bit of experience regarding how to operate it. I have neither.

Does anyone know where I could get such a thing made?

 

[flyer]

I made something like that but for a monopod. It used either an ACE or Spike's threaded adapter and I bolted a Magpul plastic Picatinny rail section to it.

With an aluminum rail it would have been stronger but still marginal in my mind.

I remember there was a .22 LR AR style pistol made by ATI or someone which seemed to have exactly the piece I needed but I couldn't figure out how to get one for a reasonable (cheap) price.

One tip: AK people seem to love putting AR stocks on their AKs so they have a lot of weird adapters that AR guys might never see...

 

[BurnOut]

Essentially, I am looking for the exact opposite of this adapter: https://www.thordsencustoms.com/picatinny-buffer-tube-adapter/

That one adapts the Sig guns to an AR buffer tube while I want to adapt an AR buffer tube (interface) to the Sig folding stock gizmo. Grr. I'll check the AK adapters, that's a good idea...

 

[GH41]

What caliber is this rifle? That SIG thing is used to SBR a 9mm pistol. It looks to frail for hard use even on a 9 to me.

 

[BurnOut]

The plan at this point is for a short action 6mm of some flavor... 6mm Creedmoor, 6SLR, etc...

I have one of those little Sig gizmos on an MPX, and it locks up pretty solid. Basically, once the stock swings into the closed position, the little trapezoid-shaped bit on the "axle" of the pivoting mechanism drops down (aided by a spring) and locks up against the beveled interface of the piece that has the pic interface built in. You can see what I am talking about in the first pic on the Sig link that I provided... they have the adapter upside down in the pic (the stock would swing to the right from the rear of the gun if mounted as shown in their pic vs. to the left when it is installed correctly).

To unlock the mechanism, I have to wrap my fingers around the buffer tube and lay my thumb axially along the top of the adapter/rear of the gun and give a pretty decent squeeze to separate the wedge fit (of the trapezoid bit and the housing) and overcome the spring pressure described previously.