I posted previously about how the sport of 3-gun spawns some radical innovations. Some are wildly successful and go on to attain widespread acceptance, some achieve temporary notoriety, and yet others are stillborn. Due to its comparative youth, the jury is still out on the X-Rail magazine extension from Roth Concept Innovations (RCI), but at the moment, it's the highest-capacity shotgun magazine out there and it allows you the ability to cram almost an entire box of shells into a tube-feeder.
How it works
Attached to the end of a conventional shotgun magazine is, wait for it, the magazine end cap. By replacing this with an X-Rail, you effectively add four extra magazine extensions to the existing mag tube, each of which is rotated into place by a spring. As a mag extension is emptied, a full one is automatically indexed into position. All up, the device gives the user the option of 22+1 capacity; by comparison, its nearest rival, the Russian Saiga, only manages a paltry 20 rounds in its drum, which is almost impossible to seat on a closed bolt.
Mark Roth, the wiry, hyperactive inventor of the the X-Rail, sent me one to install on an FNH SLP Mk1. According to the detailed instructions that accompanied it, the first order of business is to remove the existing magazine tube. Evidently, the guys at FNH don't want you to do this, as it's easier to get my brother to remove bills from his wallet than it is to separate the mag from the receiver. Two strap wrenches and the gentle ministrations of a blowtorch were needed to get the two to part company, but once that was achieved, the rest of the parts bolted up without incident.
Let's just say that if you're a wingshooter with a tendency to check your swing, this thing will cure you. Hanging a small European hatchback off the muzzle of your shotgun will achieve the same effect, but it won't be nearly as much fun. Ripping through 23 rounds of birdshot and annihilating steel targets is all part of the sport and the added weight of the extra ammo does a good job of soaking up recoil and keeping the muzzle on target. The downside is that transitions between widely-spaced targets are slower, as all that mass up front is harder to get moving and just as hard to stop, especially if you're not a particularly big guy like yours truly.
RCI have a number of options to kit out Benellis, FNs and the venerable Remington, as well as a couple of compact versions for pump guns such as the Mossberg 500, which don't extend past the end of an 18" barrel. Under development is an integrated model, which replaces the shotgun's forend and brings the magazine adjacent to the receiver - I believe this will be the next evolutionary step in Open division shotguns and if it proves reliable in competition, will probably make its way over into the military & LE sphere.