I have 3 Browning Buckmarks. All three started with 7" barrels but 2 now have shorter barrels. The current configurations: factory stock 7" fluted target, Target frame with 5.5" SS camper barrel, Hunter frame with 4" slabside. The 5.5 and 4 pistols also have Dawson FO front sights.
All three pistols have the top rear screw loosening problem and all have been fixed with Locktite.
The pistol which remained stock (7" target) took the longest to loosen the first time but once it had loosened, it seemed like it took less shots for the screw to loosen again.
Before using locktite, I had 1 screw break which required me to send the pistol to browning for warranty work (all free). This pushed me to put Locktite on all. I even put locktite on the front screw and a some where the barrel meets the frame (acts like bedding).
Also, I had grip panels loosen - Locktite and a little bit of epoxy at strategic places on the grip panel fixed the issue.
The most fun is the 4" but requires more concentration to shoot as well as the 5.5". The 7" feels front heavy and noticeable when swinging fast from one target to another compared to the short barrels.
I have other .22s besides the buckmarks (S&W 41, Ruger MKII) but the Buckmark 5.5 gets shot the most (when ammo was available).
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Between Ruger MKxxx and Buckmark - pick what fits better. both are good.
Ruger MK seems to be built tougher than buckmark.
Ruger vs Buckmark cleaning is a non-issue for me. I hardly disassemble the pistols for cleaning.