Level of difficulty has nothing to do with the issue.
At stake is whether or not free men ought to be armed. Period.
They should; to defend their liberty from all who would abuse, usurp and become tyrant over them.
As an aside, the critical components of the AR or most any other weapon for that matter is heat treatment of proper steels. The AR bolt does not lock into the breech of the barrel, but rather into a barrel extension, which is screwed onto the barrel breech, very much like a bolt actio or most all other actio types. It, the boltand carrier are made of not too common (but not rare) steels heat treated to be extremely hard, tough and wear-resistant.
I'm sure common o-2 tool steel would work. It is available everywhere at any tool supply. It is easy to heat-treat with just a torch and a bucket of oil.