A handi rifle in .500S&W would be neat.
I had visited Marlin/H&R's site several times over the course of a year back many months ago and saw that they offered 7.62x39 as a caliber in a complete rifle, but did NOT offer the 7.62x39 in the accessory barrel program.
I always thought that was pretty stupid, as the Handi-rifle is not well suited to the heavier calibers as light as the rifles are and lighter cals. like 7.62x39 and .223 are ideal for it, IMO.
They had issues with them not setting off steel cased ammo.