I’ve probably got at least four - as any “one” of the bunch didn’t do everything.
I like the Magpul wrench, and I’m considering the Avid wrench - hammer combo, I think I could dump the rest with these two.
As noted though - a number of rails now take their own wrench, either included, or separate purchase.
The investment I’m really happy with is the barrel extension wrench, Reaction Rod, or whatever the copies are called.
For a basic wrench, the stock GI USMC barrel nut wrench is hard to beat for simple, and will out last you. It usually has the 3/4 circle that catches many of the barrel teeth, and is less prone to slipping off - IMLE.
Avoids - Wheeler Barrel nut wrench - I’ve sheared or bent the lugs pins on the barrel side, and the castle nut side without reaching full torque - they are soft metal in my experience.
Other one I’d avoid spending money on - any of the flat style 3 pin barrel nut wrenches - they will work in a pinch, and I’ve used one of the GI type for years. Yes, I have one in the range box, but it’s more novel tool than a user now. If you slip with one these, it’s going bugger up the barrel nut teeth - IMHO.
If you are meticulous in your work space set up, and can keep the pin plate aligned in the barrel nut - they will work, but cheap barrel nuts will shear the lugs, and cheap copies of these wrenches will bend the pins.
Torque specs for the barrel are available online, and you don’t have to crank it to the max to be “right”. But occasionally- you’ll get a barrel nut that has to go pretty well up the torque scale to clock the nut gaps for the gas tube.
