The poor accuracy of the PSG-1 isn't an uncommon complaint. I've never shot anything better than a 1.4" group with a PSG-1 (marginally better than my HK91 with a Henscholdt scope) but I've also only run 20 rounds of Black Hills 168-gr down range with one. My match guns (Springfield M1A and Rock River AR-15) easily hold sub-minute. Talking with other shooters who've experienced the PSG-1, all seem to have common experiences, even with some decent match ammo. From the technical side of it, it might have something to do with the design of the gun--it simply can't go sub-minute. Like other HK 90 series products, it's essentially a delayed blow-back gun. To assist extracting, the chamber is fluted to reduce some of the post-firing "squeeze" of the brass to assist in floating the brass out of the chamber. In essence, you reduce the tightness of your chamber and leave an area for variation in pressure that's going to affect the velocity of your round. Variation in velocity equals a variation in accuracy. This is why match chambers in most rifles are very tight. This tightness in semi-auto battle rifles however, is generally accepted as a bad thing as it detracts from reliability--if it's tight to begin with, dirt will make it even tighter and may even cause it to fail.