I acquired Mic's book just after it was published some 19-20 years ago and yes it has some very good data some of which I have used several times...He was able to lengthen the COAL and functionality to 2.72" +/-(I think?)...I got mine out to 2.66" max with selected bullets...working on a 444 Marlin barrel now using 9.3 x 74 cases trimmed to 2.635" unfired...≈3.4" single loaded.
Way back then I think he charged $125 to do 2.60 something and $200-250 to do the longer case...don't know about today.
That front sight screw has messed up many a fine rifle's accuracy and is sometimes hard to diagnose as there are SOOOO many things that impact accuracy. It can be checked quickly by using gauge pins and should be one of the procedure all 'smiths apply but sadly just isn't...cost and economy has messed up a lot of things.
The front sight can be dovetailed in or left off(SCOPE ONLY) and an internal muzzle brake milled/drilled in for ≈1 " or so behind the screw hole relatively quickly, not necessarily for recoil mitigation but just to keep the barrel down with the holes pointing straight up and 45-60° on each side of vertical. I've done a few that way and they TOTALLY WORK.
Just like EVERY OTHER RIFLE AROUND, leverguns can benefit from several simple well known accuracy improvement procedures but I think the mindset really goes against doing much..."leverguns are just lousy shooters" seems to be the mantra...and we all know that just isn't true.
Keep it real.
