WoodTrekker has put up a comprehensive overview of their experiences with 12-Gauge caliber adapters. To sum it up in a few words, down-gauge adpaters (.410 and 20-gauge) work well, .22LR is short-range practical, but everything else is a resounding “meh.” This is result of the combination of loose fit of the adapters, short barrel lengths, and the cost/weight for each individual caliber.
Their summary of the rifled adapter results lays their thoughts out clearly:
Does it work? Not really. Yes, the adapters will let you shoot the desired ammunition. In that sense they do work. However, this is a prime example of how just because you can shoot something out of a gun, it doesn’t mean you should. The reason why I say that they do not work is because of the atrocious accuracy. I suppose accuracy is a relative thing, and for a pipe gun (which is what this combined with the shotgun actually is) it is fairly accurate, but by rifle standards, it is horribly inaccurate.
This should be no surprise for any rifle shooter. Using such an adapter is the equivalent of shooting a pistol with a loose barrel. All of the things that we spend so much time on in order to achieve accuracy: bedding the action, free floating the barrel, measuring tolerances, are not only not done here, but rather what we have is quite the opposite. We have an insert which gives us a firing platform separate from the action, it’s position changes with each shot and even every movement of the gun, and the insert is not bedded properly, touching the barrel and moving around under the pressure of the detonation. Most people blame the inaccuracy on the short barrel (either 3 or 8 inches depending on the model), but that is not the main problem. Many handguns like the Ruger Mark II and the Browning Buckmark will shoot close to 1 inch groupings at 50 yards all day long. The mechanism of the shotgun rifled chamber adapters however, prevents such accuracy regardless of the length of the insert.
The lack of accuracy is not a product of poor quality either. The adapters are very well made and are good quality with attention paid to the details. Unfortunately, the technology itself can only be pushed so far.
However, adapters that allow the use of smaller gauges and black-powder work very well. Trekker contends they add versatility to your shotgun for little weight and cost but are ultimately not practical as the shot patterns degrade faster.
Does it work? Yes. These adapters, at least in my experience, work very well. The patter you will get out of the shotgun will not be amazing (it will be similar to shooting out of a cylinder choke), but at 20 yards and maybe even more, a 20 gauge shell shot out of a 12 gauge shotgun will give you a decent pattern. When you start to go to smaller shells like the .410, the pattern will degrade much faster because of the bigger difference between the 12 gauge barrel and the .410 shell, but it will get the job done.
Is it practical? Not really. The theory behind these chamber adapters is that you get the added versatility of using whatever shells you can find. While that is true in theory, we are talking about wilderness self reliance or survival here. When is the last time you were somewhere in the wilderness, and found a box of ammunition… any ammunition? The answer is probably “never”. A Short Lane 12 Gauge to 20 Gauge Shotgun Adapter weighs 3 oz and costs $25. It will work as it is designed, but if you don’t have a realistic chance of finding 20 gauge ammunition in a wilderness survival or self reliance situation, then it is dead weight. If on the other hand your idea of wilderness involves houses, farms, and gun stores, then maybe this would be a good option. With prices of 20 gauge ammo often being higher than that for 12 gauge ammo, the benefit is not clear to see.
The only circumstance that I can think of where such an adapter could be of practical use, is if you are out hunting with your 12 gauge, and your hunting partner is using a 20 gauge, and you want to be able to bum ammo from him. Then a 3 oz adapter makes sense, and can be quiet handy.
What do you think? Is their experience spot-on or have you found them to be more useful?