I was reading Troy's magazine FAQ and I was hoping he or someone could answer a couple questions. First, I recently bought a bushmaster 10rd steel magazine that they call their bullpup magazine. any idea who makes them for bushmaster? It is a very well made magazine and it performs better then other magazines I have used but the floor plate is not labled. also, I bought their 30rd aluminum magazine and when I compare them I notice differences at the top of the magazine where it feeds from. the top forward and top rear part of the 10rd steel magazine are rounded off, while the 30rd aluminum is fairly square on the edges. whats the difference between these two designs? I would really appreciate any information you could give me. thanks. -Chris

anyone?

Ok, here is what im talking about. look at the differences in the two pictures. Why are they different, whats the purpose?
http://www.geocities.com/crizmotek/mag1.jpg
http://www.geocities.com/crizmotek/mag2.jpg

My opinion is that a full 10 rd mag doesn't exert the force on the feed lips that a full 30 rd mag does, so reinforcement of the feed lips isn't required. On a USGI 30rd Mag, the feed lips are welded to the rear of the mag providing support to the lips so that they don't spread or deform under the force of a fully compressed spring. This additional support isn't required on a 10rd mag due to less force being exerted by the smaller/weaker spring.

Just a guess, but it does make a little sense.

I guess that makes sense but with the 30 rd mag my bolt doesnt seat all the way into the barrel and then it gets jammed and I cant pull it back out. the 10 rd mag doesnt cause any of this. I first thought the 30 rd mag was maybe deformed so I checked it and all appears fine. I am using a american spirit arms lower if that means anything to anyone. Im not really sure what elses it could be.