What criminal element? I have never heard of guard dogs being "taken out" with cross bows.
I think criminals hold their crossbows gansta style for increased accuracy!
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together. You'll remember the quality of a gun long after you forget how much you paid for it.
US Army 1966-69, VFW Life Member, Retired Geek