The problem with tearing paper patches may be a function of the depth of the rifling rather than the diameter of the bullet. Many of the old rifles that were designed to shoot PP bullets had rifling that would be judged quite shallow by today's standards- on the order of 0.002"/side. You might also check out different papers. From time to time I'm able to find some very thin (~0.0015"), very tough, and thus very satisfactory rice paper. One other point- sometimes the "Chase" patch will work better than the standard double thickness patch. Why? I don't know, but 'tis so...
BTW, I hope you don't consider original Winchester M1885's to be beyond the pale as BPCR's :wink:.