cvicisso : Thank you for the kind works. You make me blush!
Jer; Yes, the lower pressures of the .45-70 do cause less wear and tear on the pistol, but when you load up the .45-70 to performance levels, (remember, the .450 Marlin is just a hot loaded .45-70 in a slightly different case) then one has as much wear and tear as the other. While the .454 operates at 50K plus, even hot loaded .45-70 loads operate well below that, say in the .45K area, so yes, in theory the .45-70 will have less wear and tear. However, unless you really abuse the gun, I doubt that you would ever see any undue wear and tear in your lifetime. The BFR revolvers are real mooses of a gun, built more than strong enough to handle the punishment of any of the mentioned rounds. The main point to firearm longevity is to keep it clean, and keep it lubed. On firearms like the .454 it is imperitive to keep the gun clean, then lub the cylinder axel and the front and rear contact points on the cylinder with the frame. You don't need much lube, but enough to act like a micro-thin barrier between metal to metal contact during recoil. I use a thick grease like MiliTec-1 for lubing the front and rear contact points and MiliTec-1 oil for the axel. Of course, you don't want to use too much oil that it gets on the primers and MIGHT contaminate them. Unlikely, but anything is possible. Honestly, either caliber is going to do anything the other will. If we were comparing a single shot .45-70 to a revolver .454, I would say the .45-70 is more versitle as you can shoot bullets from 250 to 500 and spitzers too. However, in the revolver the .45-70 is limited to what bullets are going to fit without being too long for the cylinder AND not taking up too much room in the case. That is one of the problems the .45-70 has in Marlins with heavy bullets because OAL must be kept to 2.550" or less, and a 500 gr. bullet takes up a LOT of room when held to that OAL. So, in the BFR you will likely be limited to bullets of 405 gr. or less and spitzers bullets like the Barnes Original and X bullets are very likely not doable, but I am not 100% certain about that. Both the .454 and the .45-70 have roughly the same range of bullets you can shoot in it, weight wise, and shoot them pretty much to the same velocity. Down side, the .45-70 uses about 20 gr. more powder to do so and has a bit more recoil, the .454 operates at higher pressures. Of course, you can always down load either round. Another point, bullets for the .45-70 are going to be rifle bullets, constructed heavier and are not going to expand at as low a velocity as handgun bullets will, but here we have to be honest again. When shooting a bullet of .452 or .458 diameter, if you choose a bullet with a big, flat meplat, like a hard cast lead LBT LWNGC or LFNGC, you don't need expansion. It is going to blow a hole clean through any deer from darned near any angle. The .454 has the option in most .454 revolvers (Ruger and Taurrus say it OK to do, FA says NO, don't know about BFR) to shoot .45 Colt loads in them. With the .45-70, you must shoot that. Of course, in the BFR, you have the option of geting another cylinder in .450 Marlin, why you would want to I do not know since you can load the .45-70 just as hot as the Marlin round, but you can if you want. Another point, you can find .45-70 ammo darned near anywhere. It may not be hot loaded ammo like you want, but any gun shop worth its salt will carry some .45-70 if you should need it. Same for .45 Colt ammo, and any more, I really don't think there any gun shop worth a hoot would not have .454 ammo either, so that point is a toss-up also.
From a purely practical point of view, the .454 will do anything the .45-70 will do in a handgun and do it with less powder. However, with the .45-70 you have the option of getting a rifle in the same caliber and able to shoot the same ammo. There are not that many .454 rifles out yet, and from what I understand, you do not gain much in the rifle over the pistol, maybe 200 fps. In the rifle, like a Ruger No. 1 or a Marlin 1895, you can really make the .45-70 sing, 2000 fps with 400 gr. bullets is not difficult at all. If I were making the choice, based on what I have said, you might think I would pick the .454 because in all honesty, it makes more since. But I wouldn't. I love the .45-70 and would go for it. I have five already, so what is another. By the way, I know where there is a BFR .45-70 for less than $600. It is used, but is absolutlely in like new condition for $579.95. They also have new ones for $649.95. These prices are firm and you likely will not find better prices anywhere. If interested, contact Perry at Kiesler's Police Supply, Jeffersonville, IN. 812-288-5740, ext. 4. They have one used revolver and two or three new ones that are on close out.