Olevern,
I'll have to agree with you on the bullet choice issue! I too would feel much better prepared for "Mr. Piggy" with a hard cast bullet in the .348. It will penetrate deep and go through that tough gristle plate like butter!
Now, about that Browning '71 in .348 Winchester. They are really great guns, well built, nice and tight with excellent fit and finish. Mikuro did a great job building them.... except that someone didn't follow the old SAAMI specifications for chamber throats... they are VERY short!
The .348"-245g LFNGC bullet we have in our lineup was designed and the mold cut about three years before the first of these new reproductions came on the market. Our bullet is designed for the standard chamber found in the original Wichester '71's. It fits the throat to a tee, and shoots like gangbusters. Using this bullet in the Browning guns requires one of two things. Either seating the bullet, with the gas check and base of the bullet below the neck of the cartridge, or putting a throating reamer though your gun, making the throat longer to accept traditional bullets and loads.
Since the gun has already been drilled for the receiver sight, you won't be doing anything more to collector value by having it throated, and if you intend to feed it a steady diet of cast bullets, that is exactly what I would recommend having done.
I'll give some loads here that were worked up in an original Winchester '71 in .348 Winchester.
BTB .349"-245g LFNGC/50.0g IMR 4064/WLRP/Win Brass/2143 fps.
BTB .349"-245g LFNGC/57.0g H4350/WLRP/Win Brass/2121 fps
BTB .349"-245g LFNGC/52.0g H380/WLRP/Win Brass/2104 fps
BTB .349"-245g LFNGC/42.5g IMR 4895/WLRP/Win Brass/1861 fps
BTB .349"-245g LFNGC/38.0g IMR 3031/WLRP/Win Brass/1744 fps
BTB .349"-245g LFNGC/25.0g IMR 4198/WLRP/Win Brass/1412 fps
This should give you some solid place to start with your load workups. Please remember that these loads were developed in an original '71, with a throat that allowed seating the bullet so that the base and gas check were entirely contained in the case neck, and did not protrude into the powder.
Let us know what you do with that peep sighted Browning!
God Bless,
Marshall