That's exactly the platform I've thought about too...and I seriously doubt it would be any concern at all to Remington because they have been corporately very eager to forget the 5mmRRM ever existed. They sold all the tooling for the ammo to Aguila and if there was a patent on the rifles it has long-since expired. Ruger's 77/22 would be perfect for a new 5mm as long as they didn't call it that...they could name it the "Ruger .204 Rimfire Magnum" to associate it with their successful .204 Ruger centerfire cartridge, as sort of a "little brother" to that one. They could even sell sets of Ruger American .204 Ruger and a companion 77/22 in .204 Ruger Rimfire Magnum...would cover everything from rats to coyotes...
The only potential fly in the ointment for 5mm mag bolt guns is cartridge extraction, which is why the original Remmy 591/592s have that two-stage double extractor system. The 5mmRRM case rim has to be completely supported because of the high operating pressures. Possibly, newer brass formulations could allow for an extractor cut these days? I haven't checked a .17WSM rifle to see what they did with that one regarding extraction.
Actually, my ideal long gun solution for a new 5mm mag platform would be to put it in an AR-style rifle like Alexander arms has done with the .17HMR...just use the gas pressure to operate the BCG as a delayed blowback...don't have to worry about working around an extractor cut.
I should contact AA about that idea...
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