That’s 4 MOA with bulk 55gr FMJ. The 69gr SMK is a better reference for a barrel’s capability.18" stealth according to what people say should be way better than 4moa, if it will be doing 4moa i will sell it.
a 16" tavor of mine does 2.5-3moa on a steel tula.
again, from what i was reading i do expect it be 1-1.5 moa or better. will see. may be it is an unrealistic expectation. who knows.
i was also debating between 20" and 18" but based on what i saw on forums there is no much benefit from 20", it seems, and with a muzzle thing pinned/welded it gets a bit long. a twist of 18" and length should be, probably, optimal. but, if it will not group better than a tavor - grr.
But barrels can be finicky. One might shoot a particular bullet great, and another not. You could have a match barrel that just doesn’t shoot a particular bullet well. It’s all about the harmonics of the barrel. Some people even tune barrels to their bullet of choice either with adjustable muzzle devices or set screws touching the barrel at a specific distance from the chamber. But these are extreme measures for precision folk.