The 44-40 bottoms out just past the lead . So that’s a good thing doesn’t fit in yours or a “ no go “ cal . The 44 Colt binds from the get go just a few thous. Oversize . If they fit in other 75’s u have I would suggest someone has opened the chambers in the cyl. The reloads , done by a wonderful fellow passed away , I gather he ordered special dies etc made up in a custom machine shop in the USA . If I recall , they reduced “ resized “ the 44 Colt brass down . He would then trim them back and then would have to reduce the dia . Just below the rim as u can see a “ groove “ below the rim on his reloads . Powder loads , exact measurements I can’t help with as I said he is no longer with us . I do have all the reducing and sizing dies , this n that that I recovered after he passed . He used my 75 to test and fit .
Cheers