[What type of groups can I expect from one of these guns?] -
They are not target rifles, and the external hammer has a long locktime, adding to accuracy issues - good trigger pulls notwithstanding.
A specially-tuned/accurized specimen can be expected to shoot about 2 MOA, but run-of-the-mill issue guns are much less accurate.
[what kinda of range can be accurately shot with the sliding sight?]
Many have been fired at targets/ranges as long as 600 yards, and more.
Trajectory and range estimation, however are critical issues
[I have read were these guns can have the breech open or not close correctly and run the gun when fired. Bad news.] - Yep
[Is this a real issue or the result of guns being shot with over powered loads or guns that are worn to much?] -
Real - From both worn rifle parts and heavy loads
[Is it an issue on the remake as well?] -
It is a DESIGN issue, common to all trapdoors
[Will the 32 in. Uberti with trapdoor loads out perform a 18 or 22 in. marlin with marlin loads?] -
Not really, but it depends what's meant by "out perform".
A longer barrel may well be capable of better accuracy than a shorter one, from simply a longer sighting radius.
As far as power is concerned, there are generally three accepted levels of loads for .45-70 rifles:(lowest to highest)
1) Trapdoor
2) Winchester 86/Marlin
3) Ruger/Win 1885/Browning 1885.
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