Re: PTR 91 Owners
Your expectations of the rifle will be determinative if it is a "good" option or not.
I have a good deal of experience with the HK91/G3/and clone rifles having worked on/built many myself as well as shooting the factory rifles.
First off, the PTR-91 rifles in my experience are the best of the best HK-91 clone rifles (a close race between them and the quality...before they went to SHITE...SAR-8 rifles from Springfield) with some limited exceptions of "bad" rifles leaving the factory (problems long-since resolved however). They are good quality "battle rifles" but without CONSIDERABLE time and money...they'll never compete with any of the big bore ARs in terms of accuracy. Your average PTR-91 in my experience, right from the factory, is generally capable of 3MOA accuracy or better with decent ammo/shooter/etc. With an upgraded trigger (like the Williams or Springfield I mention below), with quality ammo (NOT MIL SURPLUS ball ammo or cheaper commercial ball ammo), and with an experienced shooter, you can get them into the 2MOA range in my experience (and perhaps slightly better).
The upside to them...excellent reliability, more than suitable accuracy for what the rifle was designed for, better fit/finish on the PTRs than the OEM HK91/G3 rifles (and FAR better than any of the other clones on the market or available in the past), INCREDIBLY CHEAP AND PLENTIFUL MAGS (I paid around $75 or so for my last 50-pack of NIB aluminum mags...they run a little more these days at a whopping $2/mag)! The downside...a lack of meaningful aftermarket support for many items (as compared to the AR market), extreme HIGH cost of HK replacement parts/accessories, lack of modularity/flexibility (again...as compared to the AR market), mounting optics can be a PITA, hard on brass if you are reloading or planning on saving brass from the gun (can be resolved pretty well through installation of a port buffer (a $30 part).
+1 on a trigger job being one of the first, best things that can be done to vastly improve the accuracy potential of the HK91 and clone rifles. Williams does a fine job, as does Bill Springfield. Here are links to both sites:
http://www.triggerwork.net/hk.html http://www.williamstriggers.com/page2.html Additionally, if you have specs on the rifle you are considering trading for (like serial number/range, any barrel or receiver markings, etc.) I may be able to tell you if it falls into any of the "problem" era PTR/JLD rifles. The fluting issues have been well-documented. It was a multi-faceted issue involving both the number of flutes (10 vs. 12) as well as the dimensions of the flutes themsleves. All of the "problems" with some limited numbers of the PTRs can also be tied directly to the use of some incredibly pi$$ poor ammo (especially tar-sealed foreign mil surplus stuff) in conjunction with the fluting issues.