To me it makes no sense ... Kinda like the guy bear hunting with a 338 mag with a 500 S&W on his hip.
In both cases, Glen, it makes eminently good sense! In each scenario, the rifle is obviously the primary weapon of choice for the hunt ... but, once empty, that rifle is nothing more than a very expensive club, which any sensible person will gladly and quickly abandon in favour of the handgun to deal with an enraged/wounded carnivore of the deadliest sort rapidly closing in on him!
Correction: It was a 450-577 Martini-Henry cartridge Howda but either way you really wouldn't want to drop both hammers at the same time!
Actually, Garry's howdah pistol is, indeed, chambered for .577 Snider ... this is a Guns & Ammo video featuring the very pistol he had with him at that Muster -
http://www.gunsandammo.com/video/howdah-pistol/One thing Garry says in this video is a bit "off" ... something along the lines of "... if the tiger is still coming when you have emptied your rifle,
you'd load this thing up ..." Rest assured (and as Garry is of course well aware, despite that slip of the tongue) one most definitely wouldn't wait until then to load it ... it (or even better, a pair of them ... would be very close at hand and all ready to go!
(Another minor point, if I may: the Martini-Henry cartridge is most commonly referred to as ".577/.450" ...)