Okay, I special ordered from airsoft-unlimited.net two boxs of KA m1a1 Thompson mid-caps.
Brads customer service is great and he's a very helpful individual.
The magazines come in a box of 5. They are approx 110 rounds sometimes you can squeeze a little more, but 110 is a good number. The box says lubricate before use but upon pulling my mags out I could tell they were pre-lubed. They feed great. I let loose on full auto and emptied the mid-caps without a miss-feed.
Fitting them into the receiver is varied. I have three cyma thompson and they fit in 2 of them with just alittle tap on the bottom to seat the mag. The third was very tight in the receiver and required a whack to seat them. Im thinking the is an issue with the gun, not the magazines, as the receiver is plastic it will wear so my other two may have been more worn down than the third. So far as I can tell thats there only flaw. Even that I was able to fix with a mini file and filing down the inner channel on the magazine, I can tell the difference it makes every pass over.
The magazines are built like MAG mid-caps. With a U channel inside allowing more BBS to fit. The spring is held in place by a plastic lock bar that is held in place by a pin that goes thru the body. The seam isn't too bad along the sides of the body.
My pics made the magazine look way way worse than it is in real life. If your bold you can attempt to make 20 rounders.
I pulled the pin out and removed the lock Bar nd removed the spring. I then carefully pried open the casing with a flathead screwdriver. This did break part of the seams but it fits back together decently.
I cut about a 2" section out of the middle and then plastic welded the ends back together. More practice at this will result in a better finished product ims till debating about continuing with 4 other magazines....
I super glued the magazine back together and left it clamped to dry. Then i cut about 31/2 inches of the spring and replaced it. I now have an approx 85 round 20 round mid-cap. It needs alot of external finish work but it works and is pretty solid.
So go ahead and ask questions: