questions

[Lazyme]

...

[nicoroshi]

Thread pattern is the same as the m92.
Not sure about promags
I went with the m85 specific magazines on my rifle build.

[7,62x39]

you can't just pin the folder closed and have it be a pistol. That would be an sbr. You need an ATF approval letter for things like that.

[Schützenweber]

you can't just pin the folder closed and have it be a pistol. That would be an sbr. You need an ATF approval letter for things like that.

I am planning on a "permanently pinned" folder if that matters. There will be no way to open this into a full stock. I am searching now and can't find a definite answer or reference to a law.

As 7,62x39 already wrote - you CAN NOT have a STOCK on a PISTOL without an ATF approval, regardless the position.

.

[Schützenweber]

Lazy alright ..

Title II of the Gun Control Act of 1968:

A Short-Barreled Rifle (SBR) is defined as:

(3) a rifle having a barrel or barrels of less than 16 inches in length;
(4) a weapon made from a rifle if such weapon as modified has an overall length of less than 26 inches or a barrel or barrels of less than 16 inches in length;

A rifle is a firearm designed to be fired from the shoulder and fire one bullet at a time through a rifled barrel.

An SBR may or may not retain a shoulder stock after modification.

ATF regards pistols with shoulder stocks as redesigned to be fired from the shoulder.
Modern pistols with shoulder stocks and with barrels less than 16 inches (or overall length under 26 inches) are NFA short barrelled rifles.

http://en.wikipedia.org/wiki/Title_II_weapons