Found this website for a double rifle maker I've not heard of, nor do I know what type of action they use to build up their double express rifles.

http://www.martscustoms.com/express_doubles.htm

On the above page, click on picture for a close-up. Picture may be even further enlarged when the curser is held to the lower right of the picture and the arrowed "enlargement" box pops up.

Another page listing the large bore calibers with info:

http://www.martscustoms.com/big_rifles.htm

Then, for the .50 caliber (and larger) fans, see:

http://www.martscustoms.com/best_big_50_caliber_rifles.htm

On this last page, as you scroll down, you will see a monster of a round that dwarfs the .50 BMG. With a muzzle energy of 32,000 ft./lbs. and a range of 8,000 meters, it's called the 14.5x114MM Soviet (a.k.a. 14.5MM B-32). Also shown is a picture of the rifle that fires this round. Long-range elephant plinking anyone?

Regards,

"LightningTwice"