If you're looking for a real softball load for plinking without the recoil inherent in the off the shelf round, try using 255 grain .45 Colt cast bullets, oversized if available, over either 11 grains of Unique or 14 grains of 2400. Do NOT use jacketed bullets or you may stick one in the barrel. And use a Dacron filler behind the bullet to hold the powder in place. Since the XLR uses Ballard rifling you can have a lot of fun with cast bullets, loaded down, even in the 300-350 grain weights. My 1895SS has the Micro-groove rifling and I have struggled to find a cast load that shoots to my accuracy expectations. But for fun, I put up with it. For full power loads, it absolutely loves the LeverEvolution ammo, and I load the Hornady 325 gr. FTX over 45.8 grains of IMR 4198 for even better accuracy than the factory load.
There is a ton of published reduced load data out there for the 45-70, and they're all more fun to shoot than even the Trapdoor data, which is in reality still a buffalo killing load.
BTW, the pistol bullet loads will likely tumble, so they are very short range loads. Unless you can find some that are so completely oversized as to make .458". Mine drop out of the mold at .452-.453 so they don't seal the bore. They sound like little buzz saws exiting the long tube of my original 1873 Springfield.
mike