HC do you have a link to the home page of the site were you are getting all these nice pics of cartidge specs?????
that 300 rem mag might make a very nice .50x1.5 type round indeed. Hard part would be the large bolt face. maybe you could some how use a bolt and carrier from your 45-70 build? the rim of a 410 SG is .536 perhaps a siaga bolt could be used or possablly it could be rebated. Think it might be getting into the to much for a AK area again though.