Rifle Bore ?

[Dana]

Hello, looking at a Spencer that has newer barrel, bore is about .505, groove is about .528 is this a 56-50 or something else ? Does one try to get a mold that is .0015 over groove size or bore ?

Thanks Dana

[Herbert]

.528 seem large for a 56-50 but posible, .518 to .523 have been the ones I have measured,but groove diameters varied a lot,how many grooves has it got.For best acuracy I have found .001 to .002 oversize to give me the best acuracy,you may have to open up your FL sizing die to enable the right bullet to fit or make 56-52 cartridges they would fit that chamber much beter but were to find a .530 healed bass mould,would have to be custom made I would think,I had one made up 35 years ago but the maker is now dead