Welcome,zzzzero
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I don't know if I'll be much help just got my 45-70 Encore barrel today.I did have a Super-16 45-70 contender barrel but,I got the Encore bug and sold it :cry: But that's ok got me a 16 1/4" barrel now.Several thing come to mind.....
#1...Have you shot a Contender before..?
#2...Free-floating will help just use some black tape folded several times and place it between the forend and barrel cut a hole in the tape push the forend screws in and screw the forend on.*Note if this works you can replace the tape with nylon washers*
#3...Practice,practice,and practice shooting.
#4..I don't like muzzel brakes on any barrels if you need one it's to big for you to handle.*note*- This is just my opinion.
#5...I would sale the 12" barrel and get at least a 14" tube or better yet get a 16 1/4" barrel. If you cut off the brake on the 12" tube you will have about a 10" 45-70 Not my idea of fun.This is also my opinion