Made a M4 magazine adapter for a DE M56 multi-shot airsoft shotgun. Pint as is with supports enabled. Support structure is probably going to be in the feed tube, there wasn't a way to get around that. Clean the feed tube with a string, wire or a screwdriver to clean the support structure out. There are two files, the first is the adapter and the second is the part that stops the loading door from moving. When first inserting the adapter it might not go in easily, after fitting it in a couple of times it should get easier. There will be support structure under the release lever, be careful and cut it with a hobby knife or utility knife. Do not insert a magazine until you have broken the release lever free from the support structure. Cut a pen spring in half for the release lever, it's not easy to fit it into the space behind the release lever. Uploaded a new mag adapter design to deal with feeding issues along with breaking after a couple of uses.

I've uploaded new updated files that hold the mag in better and is more reliable. Everything is 3d printable except the part that holds in the release lever. I used a nail that has flat head with a 2.48-2.9 mm diameter shaft and cut it with some wire cutters for length and fit. Make sure there is no support structure in the feed tube. Used 0.3mm for the adapter and 0.2mm for the release lever and springs. Make sure there is no debris in the feed tube before using. I included a third spring that should help if the other two are too loose or keep falling out. If the mag release lever is too lose to goes too far in the mag well then a bigger pin 2.7-2.9 mm might be required.