Follow up: Started my velocity test back at 90 gr as above. Got 1540fps, right at my average for that amount of powder. Went to 100 gr, 1647fps. Next 110 gr, 1772fps. Hum, I'm surprised at this point. Don't know why but I just was expecting velocity to top out not far over the 90 gr loads. So put in 120gr, get an average of 1844fps over 10 shots, +/- 60fps. Cool barrel gives the slower speeds. Still keeping 3" groups at 100 yds, a welcomed surprise. I stopped there and decided that will be my hunting load.
I set the scope 6" high at 100 yds. Ballistic calculator says that should put me sighted in at 200 yds and -27 at 300yds. Stopped at the 300yd range on my way back from the deer lease and shot an average of -33 1/2" (28 to 38 inch drops) with a 14" group size. There were on and off drizzles, maybe the air was thicker than my calc inputs.
Interesting (more so if I knew what it indicated) the horz spread at 90 gr powder tightened and the vert spread opened at 120gr. Gives me a more circular group shape.
A side note, I retested some all metal bullets. I would dearly love to shoot those and eliminate the one more loading issue / concern of the BOR Lock bullets. It's weird, I've tried a 3 different brands of all metal bullets and they at times seem fine (fairly tight groups), but then for unexplained reasons, things go wonky (flyers and open groups). I also tried the PowerBelt brand bullets. They shot well, but then I noticed pieces of the Belt hanging in the moderator. Oops, just like they said in the manual! Seems the Maxim 50 (or at least mine) just likes some type of saboted bullet, but the BOR Lock looks to be the only one the survives the trip thru the moderator. I've bought so many bullets that aren't gonna work in the Maxim that I went out and bought a sister pistol, without the moderator, so I can shoot up all of them.
I will say I think the BOR Lock does help with powder fouling, like the package says. I stopped swabbing after every few shots because I wasn't getting any resistance with loading and there didn't seem to be degradation of the group size. Not thoroughly tested, but I'm beginning to suspect it does better with a fouled barrel. That's my plan for hunting. Shoot some practice shots to foul, then load and go hunting. As mentioned, the cold shot is a little slower. I noted 1" lower at 100 yds.
Wish me luck, I take off next week for a mule deer muzzleloader hunt in NM. Just gonna have to tell the guide that we'll need to belly crawl another 100 yds closer!