Brought it home and went thru the instruction manual. Kinda disappointed as it was pretty much generic. Says nothing re shooting shorter cartridges in the 460 chamber ~ in fact if it weren't for the marking on the gun itself, one would wonder what it was. Guess the printed mat'l hadn't caught up w/the HW yet.

Wonder if one could shoot 2 3/4" 410 shotshells thru it?

Did note its not to be dry fired tho ~ Came w/an extra front sight. Fitment seeamed better than Ruger.

Throats meas apprx .4523 and grooves are supposedly .451 but haven't meas'd it yet.

Magnum Research has not changed there manual in a number of years. My 500 Mag BFR that I bought in 2002 cam with the same manual I bought with my BFR 45-70 in 2007. You are right, not a lot of information there.

As for the 410 shot shell, I would not do it, even if it fit.

Let's face it, it is a BIG Ruger, pretty standard fare. How much instruction is needed?
The .460 will shoot the .45 Colt, .454 and the .460. Not much thought needed is there?