Blast it all, when this question popped into my mind, I first went to Woodleigh's site. Their bullet list recommends a minimum impact speed of 1900 fps for the 270 RN, which rather surprised me. In looking again, DoubleD, I see this may be a typo, for their upper impact speed is only 2400 for it.

Thanks for all the other recommendations. Some of them had escaped my attention. Hey mbogo375, have you tried the Hornady 270 RN at these low speeds? I've no experience with any of their RN bullets, yet.

The 235 X at 2200 seemed viable since it would still be going about 1900 at 150 yd; but I do fear it might be stouter than the average X, which opens down to about 1800. The North Fork bullets were the only others which occured to me, and they also look to be marginal for this use.

Holmes, the gun exists only in my mind's eye at this time, so I've no powder reports to give, sorry. (A few other current falling blocks came to mind, and I added them to that list.) I had tentatively settled on the .35 Win. for this gun, but a .375 2.5" at the same pressure seems worth considering. Ponder, ponder, ponder...