The M1014 unlike the M4 has a fixed modified choke and thicker barrel which takes all ammo, the M4 has removable chokes if needed & the barrel is thinner at the exit. The M4, I wouldn't be shooting slugs with, that's just me though.
I have a M1014, and slugs are no problem. Thats what I and everyone else used in the military as well. The M1014 shoots whatever you put in there! It was designed for the Military and that's what we shoot along with 00.
Wiha? If that's what u mean yes, I looked at those too, I have a lot of Wiha tools, and they make great stuff. The torque wrench's they make are no doubt great, but they were just a little too pricey for me.
I think in this instance the polymer, plastic, etc... would be more desirable, at least to me. When leather gets wet it stays wet, not good for batteries and such. Thats just me though, someone else may love that.