The .50 Beowulf upper can be dropped on to any standard AR15 lower. The upper comes complete along with one 7 round magazine.
Alexander Arms does offer the Beowulf with a factory installed muzzle break as option.
As far expense to shoot... A box of 50 Speer 325 grain hollow points can be bought for $10.00 or 20 cents a bullet Powder and primer will run you about 5 cents per round. So total reloading cost is 2 bits a round. If you compare that to loading .223 with Sierra 77grain bullets you are only 5 cents a round higher. Of course, you are not going to fire as many Beowulf rounds in a shooting session as you would .223 Remington.
Only thing that would make it expensive or inconveinent to shoot would be you dont reload. If you dont reload, do what a friend of mine does, he comes over, spends an afternoon and I load up a 400 rounds for him while he does other fun jobs like depriming, or trimming other cases.
Accuracy wise, I have been shooting .5 inch 3 shot groups at 100 yards and took it to 200 yards and was shooting 1.5-2 inch 3 shot groups which given the bullet is pretty good. This testing was done with a 4.5-14x scope, but for its intended civilian purpose, a trijicon reflex site is ideal for deer and boar at 25-200 yards.
Recoil wise, it does have a push to it, but then again a 325 grain bullet will do that. A friend of mine (who is recoil sensitive) and his 10 and 12 year old boys shoot it using a PAST recoil pad on their shoulder.