AGC of Marriottsville in Baltimore County, has two steel pedestal mounts about three feet high, that are made for a pistol Ransom Rest. One is on the far right firing line at the 100 yard Barnes Range, the other, is on the left side of the pistol range firing line. You'll have to rent or purchase a Ransom Rest. You can call the gunsmith shop...called "Guns and Roses," located over in Middle River --- and the gunsmith named John --- might be able to help you out with a Ransom Rest; who is also an upstanding member over at AGC.
If it is a 80% AR lower, it will not get you hurt if it doesn't work. The most that can happen is that 1) it doesn't fire, 2) it doesn't reset, 3) it won't feed etc..
The upper is where the cartridge is located and the pressure is contained. Having had a few and seen a few more Ka booms in AR's, the upper somewhat disassembles and the lower bulges. There have been a few more violent but they are the exceptions to the rule.
If you are want, you can hold it on the bench, with your right hand and support the stock with your left. Throw a double folded towel over the action and pull the trigger.