This is just an experiment to see if using the lower half of an MKA 1919 10 round magazine could effectively add capacity to other types of 12 gauge magazines.
For this experiment I used a Panzer Arms 5 round magazine from a BP12. That said, if the floor plate of other magazines has a similar sized slot, there is a good chance that it would work on those magazines also. I don’t think this will work with other polymer magazines as the slot is much thinner for metal magazines. Anything is possible though, so some careful removal of material with files and a Dremel might allow it.
Obviously, when tinkering with incompatible parts, there will be some adjustment, dial in, sanding, filing etc. It’s not plug and play. But for anyone looking to add capacity in a DIY way, this might be what you are looking for.
I have found the MKA magazines are cheaper and widely available, while many foreign made magazines are more costly, or simply do not exist. While there are several companies that do off extension or modification kits, they are often back ordered.
Again, this video was just to test proof of concept, and see if it would work under the best possible conditions by manually and carefully loading and unloading. Whether it will actually function in the shotgun is another story for another video.
**As always it is important for the viewer to be familiar with the laws of their state and country before adding capacity to magazines. It may be a crime in your state or country to create magazines of a higher capacity than the firearm was originally imported with, or sold with.
Legal restrictions on magazine capacity can change quickly too. So make sure to check the most current laws where you live before attempting any modifications to your magazines or firearms.
In addition to legal issues there are also safety issues that can result from modifications to firearms and accessories. Modifications that result in dangerous malfunctions or breaking of the law are to be avoided at all costs.
Anything you do is at your own risk, and I do not recommend anyone try this at home. It is simply an observation I made while working on the MKA 1919 magazines, and I think some people will find value in the possibility of adding capacity to magazines and firearms that don’t readily have an aftermarket where affordable, pre-made alternatives exist.
If you are able to access affordable, premade magazines from a reliable manufacturer I would recommend that over trying to make or modify anything yourself.
There is also the possibility of this working with large rifle rounds like .308, 30-06, and 7.62x54r, provided the double stack configuration didn’t bind up at the transition. But again, this is purely hypothetical and would likely involve a lot of elbow grease to get everything to feed reliably.