cmidkiff said:
PTR91.com
They purchased used H&K machinery, and use it to produce high quality clones here in the US. They do use a heavier barrel than the originals, making factory furniture a difficult proposition... and they use a push button mag release rather than the original paddle type (since the accepted conversion to keep from allowing select fire trigger groups gets in the way of the paddle). Other than that, they are nearly identical to an original H&K.
I have a surplus G3 wide forearm on my PTR-91, and it fit just fine with no mods. Prior to that, I had a surplus G3 narrow forearm (with metal heat shield), and it fit just fine, too. So even though the PTR-91 barrel is heavier, I've never seen it interfere with furniture in any way.
Also, the PTR-91 mag release is identical to the one on the H&K 91, which is of course the semiauto version of the G3. On the G3, the forward push pin attaches the lower receiver to the upper, and its sleeve (on the upper) serves as the axle for the paddle mag release. BATFE required deletion of that sleeve to make it impossible to attach a full auto fire control group to a semiauto upper. H&K took the easy route of simply deleting the paddle, too, and making do with a push button release. JLD Enterprises (the original manufacturer of the PTR-91) simply copied the H&K 91, which they had to do in order to legally manufacture the PTR-91. If you build a G3 style upper with a push pin sleeve, you've just built an illegal machine gun.
There are gunsmiths who do paddle mag release conversions to semiauto MH 91 and PTR-91 uppers. They are legal but expensive. Parts run around $100, 'smithing runs another $100-200, and then the upper needs to be refinished. Total cost is often $400-500.
Another option, and one that I took, is the Tac-Latch. It's a drop-in part on the H&K 91 that costs around $40 and gives you a very usable paddle mag release that is a little different from a real G3 paddle release, but works just as well. On the PTR-91, you need to make a slight modification to the Tac-Latch itself to get it to fit, but the PTR-91 receiver itself doesn't need to be modified.
Incidentally, the PTR-91 is built on machinery that was purchased from Fabrica Militar de Portugal (FMP). FMP built the G3 under license from H&K for the Portuguese military. Many early PTR-91's (like mine) also have surplus FMP parts in them, but I understand that more recent models are built almost entirely with new, U.S.-made parts.