It's a single grub screw to remove the barrel... I don't see a good reason to not remove it. My zero is pretty much always dependable, even removing and reinstalling.
I uee a ball bearing rod with jag and patches so they're pretty tight, and Gunzilla. The lead is gone in 1 patch and most all the black in 3 or 4. The breech oring is slightly larger than the bore so you don't even have to remove it. I wipe the chrono tube after, as described above, because the cleaning process will splatter the inside of the tube. Takes 5 minutes at most.
Pull through cleaning will not remove any lead, in my experience.
How often I clean is dependent on how fast I'm pushing the projectile and how dirty they are. I generally clean every couple of hundred as I like to check for lead and I expect high accuracy all the time. I've been shooting the 20 cal 13.7s @ 810 for a while and wouldn't probably clean for many hundreds of rounds unless I put a bunch of 15.89s and slugs through it.
Bob