OK hunter,
As I posted earlier, I have three full-sized Leupold scopes mounted on the three barrels I own, and two of the three have 50mm objective glass. As a personal note, I feel that the 40mm scope with medium height rings on my .45-70 is esthetically more pleasing than the 50's with high rings I mounted on the other two barrels, but to answer your question, the rifle is definitely substantial enough for the larger scopes (given my concerns I have noted regarding the Durasight rails). The cheek weld is different of course, but good on both height mounts. To date, I have fired somewhere in the neighborhood of 90 rounds through both the .270 and .300 Win Mag, and have not seen any evidence of the POI changing.
I have attached a photo of the .45-70 barrel with the 40mm 3X9 mounted on the receiver, and the .300 Win Mag with the 50mm 4.5X14 (30mm tube) and .270 with the 50mm 3.5X10 (1" tube) below. I chose the 50's for the .270 and .300 because I anticipate shooting over much greater distances in low light conditions and wanted as much light-gathering capability as I could afford, on those two barrels. I purchased the .45-70 to meet the primitive weapons requirements here in MS, and will be using that configuration in tight, wooded or brushy areas, at relatively short ranges inside 200 yards. By the way, the separate forearms on the .270 and .300 are not necessary since a standard taper forearm will fit both barrels, it was just a personal choice to spend the extra $35.00 to keep the two systems completely separate.
One other note...If you prefer iron mounting hardware over aluminum alloy for the heavier recoiling center-fire ammo, I would recommend Warne Weaver permanent mounts over the Leupolds for mounting Leupold scopes on these barrels. The Warne mounts are a bit lower in cost, seem to fit the rail better, are more streamlined in appearance, and you won't run the risk of scratching the scope tube, as you might with the snap-on style of the Leupolds.
Good shooting! ...CC...