The older 1886s and ofcourse the model 71 could be converted to 50 AK, but then the receiver for the older 86's were the same for all chamberings, including the 50 cals. An interesting note, all 50-100's, and 50-110's had to be carefully fitted by knowledgeable employees, as they had a good deal of difficulty getting the big fat cartridges to feed reliably, the big difference is in the carrier group, it has to be modified to handle the larger rounds. I have an old 1886 that I bought for a project, I wanted a 50AK, it was going to be a low pressure gun, for even though it wears a 33wcf barrel, the receiver is from 1896 according to the serial #. Alas the 50 cal bug wore off, and I am sticking to the 45-70, I am working with a Ruger #1 now, and am in the process of buying a Marlin stainless guide gun with un-ported barrel, stainless is good for the weather here in Alaska. I know McGowen does the 50 cal conversions, as that is who I was looking into doing mine.