The damned thing is over 4 feet long. Even with the bipod folded, it'd snag on damned near everything. That made it hard to walk quietly through the bushes. Also, when equipped with a bipod, a 100 round belt, and a sling, the SOB weighed about 30 pounds. You carry that thing all day and the sling would push down on your shoulders until it felt like your neck was 2 feet long. It was nice to be able to engage out to 1100 meters, but those kinds of long shots are really pretty rare.

One problem with carrying too many different calibers is that it makes logistics more difficult. Keeping to at most a couple calibers makes resupply and ammo sharing much easier. That's why NATO standardized on the 7.62mm round. Back in WWII, you had the M-1 Garand (.30 caliber bottleneck cartridge), the M-1 Carbine (.30 caliber straight-sided cartridge), the M3 Greasegun and Colt pistol (.45 caliber), the BAR (basically 30-06), and the .30 caliber belt fed Browning machine gun. You might have all these different weapons in a single unit. Throw in the 9mm rounds used in the Sten gun and the .303 rounds used by our British allies along with various other weapons like Bazookas and mortars and resupply was a real problem.