The HK91 is the semi automatic, civilian version of the highly regarded G-3. This rifle has what are probably the best battle sights of any rifle in the world. A post and ring sit up front while the rear sight is a rotating drum with a series of differently ranged apertures around it. The gun is also the hardiest of the lot. It's delayed roller block action has no gas tube to be bent or clogged as in the M-16; there is no long delicate operating rod as in the Garand/ M-14, and no gas port to clog as in the AK-47. The gun is not dependent on propellant gasses, so the burning rate and residue of the powder have no effect on it. The power of the load is also not a factor in the reliability of the gun; any load will feed and cycle the action. It's size and weight are almost perfectly suited to the cartridge it fires, and it has good accuracy. The delayed roller block action, keeps the gun locked until the base of the bolt is forced back enough to cam the rollers out of their recesses, and allow the bolt carrier to move back.
Ahh, gotta love the HK. . .
Ergonomics of a cinderblock, a bolt-lock that takes two men and a hammer to operate, weighs a full pound heavier than similarly composite-stocked M1A (despite the stamped steel receiver vs the M1A's machined receiver), and a fire control group that requires thumbs the size and strength of a gorilla to manipulate. . .which is great, if you're a 6'6", blonde Aryan named Dolph.
It's trigger feels like two bastard files rubbing against each other*, reliable magazines are almost impossible to get unless you've recently won the lottery and have a connection deep within the labyrinthine maze that is known as Heckler and Koch (and let's not even talk about getting OM replacement parts, hell, you're better off trekking up to the Khyber Pass and having the guys up there make you one from a piece of railroad tie or Toyota leaf spring with a file and a hammer. . .you'll get it faster and be absolutely sure of the origins).
Wanna reload that brass? Not with this baby. . .that much-vaunted fluted chamber destroys the brass, and what isn't mauled by the chamber gets a thorough MMA-style ground-and-pound workover as it ejects.
Hell. . .now that I think about it. . .maybe it is everything Manly.
* references the SR9 version I have in the safe. The trigger is absolutely beautiful on the MSG and PSG (I only have the MSG, but got to use a PSG many years ago, as well as one of the Vollmer conversion rifles <sigh>).