Is your objection to execution by gas, or execution at all?
I agree that the death penalty is wrong. But if you are going to have the death penalty gas is probably the most humane way to do it.
Most AR-15 in the USA are used for small game, it isnt even powerful enough or suited for large game. Frankly, its just far too weak of a rife to be the best choice here, you'd want somethign more powerful to be humane.
@freemo
And probably more cost efficient. One .50 AE round should take care of business.
@stux