Although Uberti's rifling may not be Winchester historically correct, it is what it is. My rifle, in 45-60, has a bore diameter .450" and groove dia. of .457". Right from the get-go, I was disappointed with the out of the box accuracy, but with perseverance, I am getting acceptable and fun shooting. A lot of the credit for this I attribute to Silver Rings and Tom Horn, or this site.
My rifle felt like it had a tight spot in the middle of the barrel, and it leaded badly with a variety of alloys, bullets and powders. But still, I could see some light at the end of the tunnel, and all this taught me how to thoroughly clean my bore.
These first couple of targets I present, shot in the fall of 2014, showed that the rifle had some promise, so I persisted.
This target was shot with 14 gr. Trail Boss and BACo's 300 gr. bullet, in this case from re-claimed .22 cal lead. It leaded the bore and subsequent targets's accuracy diminished.
This target was shot later the same month using 41.5 gr. IMR 3031, and the same bullet as the target above. Again, first target fine, and leading ruined the following shooting.
This target was shot using Lyman 457122 in a fairly hard alloy and 14 gr. Herco powder. Same result as other targets, but serious leading ruined everything to follow.
This target used the 300 gr. Lazer Cast bullets and 14 gr. of Herco. These bullets are super hard, and though they produced a nice group from a clean rifle, the groups thereafter were poor and worse.
So far there is consistently good groups from a clean rifle and because of leading in the bore, things go in the toilet in a hurry. Advise from Tom Horn has made a big difference. I fire lapped the bore using pure lead 300 gr. slugs a light charge of powder and Wheeller Engineering lapping compound. This consists of three grits of grease lapping compound impregnated into the lead by rolling on a glass plate with a steel plate. I loaded 25 each of course, medium and fine grits and shot them slowly but without cleaning for the entire exercise. I then cleaned the bore thoroughly, and finished by polishing with JB Bore paste. When this was finally cleaned away, I had a noticeable smoother and polished bore.
My next test used up the last of those pure lead bullets lubed with SPG over 14 gr. Trail Boss. All this shooting was at 50 meters in pleasant winter conditions, and the rifle carried the Montana Vintage Arms mid-range aperture Soule rear sight and a MVA low profile globe front sight with an aperture insert. Shooting was from a bench. Here's the result on targets...
Target shot with 300 gr. BACo 457300 pure lead bullets lubed with SPG over 14 gr. Trail Boss.
Same load. Now, after a session of 30 - 40 rounds, fouling pushes out with two dry patches and there is only a little dust for lead in the bore. I still clean the rifle the same way, first with solvent, then dry patches, and polish with 'lead free' patches and JB Bore Paste. I think the better the bore is, the better the accuracy will be. Now I can confidently hit a 12" disc every time offhand at 100 meters.
But I'm certainly not finished in this accuracy quest yet! I want to try paper patched bullets in my '86 next...