Ken Water's .375 on the .303 case was a good one. He barreled one up on a Ruger #1 action, but kept the loads soft. I'm sure they'd work well in a #3.
; If you need his data, mail me.
; If one uses the .444 marlin case, ballistics are a couple hundred fps higher, bringing the 270gr. to around 2,200 to 2,300fps fps in the Enfield making it the equivalent of a rimmed 9.3x57. I would be surprised if the .303's magazine didn't feel them just fine, without alteration. The Enfield's extractor will actually work well from the little .223 case(#4's only) to .45/70's, again, without alteration.