1) where did you get a Winchester EL barrel?
2) was it an old barrel, or a new Miroku barrel?
3) who did the work for you?
The barrel was taken off an EL that was converted to 50/110. The work on the B-71 was done in Australia, so unlikely to be of value to you. There are a few changes I made to the way the mag tube is held on that are worth doing if you go down this path.
Let me also say that had I known what I know now I would not have done the conversion. Why? In most of the 1886 rifles with the right bullets (bore riding designs) you can cycle and chamber 45/90 length shells and duplicate 45/90 ballistics with a stock 45/70 chamber. The only possible disadvantage is trying to duplicate really high velocity loads using shorter bullets, but who really needs a 300gr pill doing 2600 fps. Most 300gr pills aren't designed for that speed anyway.