I found you still have to scrub, just less. That said, I've yet to lead a Benelli bore to the point patterns suffer. Also, I find low recoil slugs, say, under 1300fps actual MV, lead far far less than 1400+ actual MV slugs. Wayyyy less. Truball is the worst, due to it being kinda hot, as well as the polymer ball jamming the skirts into the bore.
Pistol grip is okay in NY as long as it's never collapsible and limited to 5 rounds, and if you're 922r compliant then you can go to 7. My understanding of it here, anyhow.
What CAUS said; the Mesa Urbino sounds like a good fit for you. I had one and took it off because I wasn't fond of the quality or means of attachment. Since then I run a field stock with a limbsaver buttpad, and while not as much control for recoil as a PG then again an M4 has a bit less than other shotguns and a field stock just feels natural for me. I don't have any optics or rail, lights etc either I've stripped as much as I can off the gun and stippled the fore end and stock for better handle.
Very nice and informative! Dr. Unob Tanium performs M4 colonoscopy.? A clean bill of health, no polyps or lesions detected.
Only 400 rounds? I would've thought you fired a lot more than that!?