So, basically, there is to many variables across the spectrum, because I haven't even broached ammo consistency, yet
I mean, come on, we have steel cased, bi-metal jacketed rounds mass produced at a million plus rounds a day with outdated worn equipment, dubious quality assurance, with a round here, a round there inspections. All the while being built with components made by the lowest bidder. I mean x39 isn't and was never designed for or by any means some hoopty Lake City uber target grade blow a gnats azz off at 2million yards ammo, heck it ain't even as good as Swiss GP11 everyday run of the mill milsurp stuff. It's cheap commie ammo from commie weapons which used correctly and within it's limitations, do the job as intended, put bunches of holes in stuff.
But,
in theory, just eliminating the ammo aspect, controlling that aspect alone, should contribute greatly to accuracy. In the same theory, you could conceivably create a load for bayonets in and bayonet extended, because each different loading should or could create a different barrel harmonic.
OR!!!!
Just load, shoot and enjoy the dang thing, repeat, most importantly learn it inside and out, and quit making it harder than it really is.