In response to the barrel sleeve question and "why". It has been my experience that I shoot much better with it than I do without it. I believe this is due to the decreased wobble due to the added weight. (physics). The firing characteristics are not that much affected by the added weight but my hold certainly is......and I don't pull the gun off nearly as much with a less than perfect trigger pull.
I've tried it both ways with the same guns (HW55T and Walther 55) and my groups are typically half as large with the sleeve. The sleeve makes me look much better than I really am........I'd put them on all my guns if I could.
To quote Don Nygord "Don't stand there all day admiring the wonderful sight picture" or somthing close to that.... because it will go to hell a little quicker as the muscles tire sooner with the added weight. As far as being a weightlifter, it doesn't hurt. Shooting on a regular basis will build up the muscles in a short time.
My bathroom scale shows the Walther 55 to weigh close to 12 lbs. with the sleeve and the lead in the forearm...and the bathroom scale wouldn't lie...would it?
I've used adhesive wheel weghts on my pistols as well with the same results.
I'm hoping to reach the level of "mediocre" in my shooting endeavors.
After 35 yrs of trying, I've had to admit that I'm not going to win any marksmanship awards but it's sure fun trying and I've met some nice folks in the bargain.........not all bad, eh?