Re: PTR-MSG 91 Preimeter rifle
The PTR MSG-91 Perimeter rifles are hit and miss in my experience (PUN INTENDED). I have seen some that were MOA capable with match ammo and others that hovered closer to around 2MOA. Scope mounting on the MSG-91 is not a problem and not expensive as PTR welds on a picatinny rail to the receiver of that model so once you have an optic and compatible picatinny rings, you can mount away without incurring the expense of a claw lock mount or a B&T flattop mount adapter. Also, because of the Magpul PRS adjustable stock, getting a good cheekweld and sight picture with optics mounted is much easier than with the standard G3/HK91 stock. You still have to deal with the OAL of the scope you select because of possible interference with the forward cocking handle and the scope's bell.
Like folks have already said, reliability is good. The gas-retarded, delayed roller lock action is VERY reliable under a wide range of conditions/environments.
It all depends on what you want to do with the rifle and whether it will meet your needs though. I will tell you that for the money PTR wants for their MSG-91 ($2k give or take), you can get a DPMS, Armalite or other AR-type semi-auto that will run circles around the PTR in terms of accuracy and will cost you a good bit less.