If one wants to enter this aspect of the debate one should do so 'armed' as it were, and most people discussing this 100-rd capacity, as well as semi vs auto vs revolver or shotgun are not. I used to teach people how to fix guns and it always amazed me how even a great many of the fairly experienced troopers treated their weapon like people tend to treat a lot of mechanical or electronic objects, complex and arcane things not to be screwed with except maybe by rote. In reality guns are stupid simple, I'm not much of a gearhead and I could assemble a functional 'heavy' machinegun with equipment available in a hardware store and the tools lying around at home, though its accuracy and durability would be marginal.

Fair warning, I'm going to go into explanation of gun function here, though I'll avoid technical jingo as much as possible

And this is the funny thing about guns. The ones people think of as especially large and dangerous are the big clunky ones with the simplest function. Precious little separates an automatic weapon from a stapler, engine piston, or potato gun in conceptual design. The same principals apply. Other than some clever improvements that once discovered were 'Oh duhs' and a few chemical and metallurgic tricks that actually aren't in most firearms anyway, the field is stagnant. The M2 Browning machinegun has been the workhorse of the Army and lots of other armies for the better part of a century and the ones in most unit armories are older than the soldier's parents, you just switch out warn out parts, mostly barrel and bolts pieces, and I don't doubt our own kids will still be using them. They are incredibly simple.

Assault rifles aren't, they are pretty complex. They are made complex not by being compact but by being non-automatic. Essentially it is the 'closed bolt' design - the thing that makes them inferior as fully automatic weapons - which is the main source of complexity. Further complexity is 'burst fire', where one trigger pull fires a set number of rounds. Converting a semiautomatic with no built in auto to an auto is not the easiest thing in the world but principally involves removing things, and I could sit anybody down in a halfway decently equipped homework workshop and walk them through a conversion. So there is a false premise that bigger is better, ironic in this age of electronics, that screws up the debate. A pistol can be made fully automatic, a 'machine pistol', and you don't see these much because they are terribly stupid weapons... unless you are simply trying to unload ammunition into a crowd. Since in military conflict the enemy generally does not cheerfully bunch together by the dozen ten feet away from you, nobody manufactures many of these. Though you can build one at home.

So that brings us back to this so-called '100 round capacity' and how dumb attempting to regulate it is. Especially if it is a belt-fed weapon. In a belt fed automatic weapon the bullets are tied together, the originals just used canvas cloth for the purpose, modern ones use little 'disintegrating' links that just fall off the casing when the reload occurs. Very simple, though if not done well you can get a lot of jams, same concept of why you buy a shovel or axe rather than building one of your own, industry can do it better and cheaper. Banning shovel manufacture won't eliminate the shovel. But a 'drum' where belt ammo is concerned, is simply a container, built fairly sturdy though it can be a canvas bag, that attaches to the weapon and has the belt inside it, where it can't have all 100 or 200 or more rounds hanging there adding their weight. You could achieve similar results by holding the belt near and level to the gun... which look cool but is retarded, or by hanging a lady's purse full of ammo just under the thing. They are not complex, the only reason they are built on the sturdy and expensive side compared to, say, a box for cereal, is because people tend to accidentally smack their gun around and drums and magazines tend to take a lot of abuse. So banning '100 round drums' is like banning tin cans, you can still use a mason jar or ceramics to achieve decent canned goods, and if you're planning to eat the food the same day or next, it's pretty redundant. A soldier will be slogging around with a weapons for weeks between firing, bumping into stuff and damaging the drum or magazine, and sturdy improvements are relatively cheap, thus we have them. Same applies for the linkage itself, almost anything will do the job, I'm not sure I'd feel comfortable using thread or yarn, you'd need to play with it a bit to find a decent setup, but they were originally cloth and they've played around with platic and resin ones, no difficulty getting them to function but getting them to be 'significantly better' is an issue, our presumed rogue nutjob doesn't need better or even equal. I don't know that I'd put much faith in an ammobelt made of tied yarn and loaded into a cardboard box but it could work, and fabricating your own sturdy one of military grade wouldn't be complex, time consuming, or require special items we could track, even a standard disintegrating metallic belt, strip of metal and some hand tools.

Now, that's belt ammo, the mainstay of open bolt automatic weapons. Semi-automatics favor the magazine, no belt, and the closed bolt (the more complex one). Here after the bullet is fired the bolt bounces back from the firing and hits a spring, ejects the spent casing then comes forward on the spring recoil bringing another round up from the magazine, which also has a spring in it. There are many ways to build the design making it a complex subject but a conceptually easy one, each method is very simple itself. Manufacturing one at home is trickier than a belt fed one, but then the hardest part of forging a gun from scratch is making a decent barrel anyway, if you don't give a damn about accuracy or lost efficiency you really could just use a sturdy metal pipe.

So, magazine capacity. There are three limiting factor on this. First, practicality. Changing out a magazine is a speed process with practice. That practice is best done while moving and trying to do it at weird angles but you could practice to your heart's content in your own apartment. Most people would be able to switch magazines in a few seconds with even an hour or so of practice, getting good enough that you can do it while jogging or crouched or lying down with speed and no conscious thought takes more, but brings us to the other part of practicality... a large magazine is a large rigid object that can bang into things, get in the way, and doesn't store well in pockets. A two foot long magazine would store a lot of ammo but would be a bitch to operate. More you can't make arbitrarily long reliable objects deriving their mechanical forces from a spring.

Ways around this. Double column magazines are fairly practical, literally just a magazine with two columns of bullets or the casket design. And finally the drum. Unlike a belt drum which is just a box or bag for bullets, a drum magazine which requires slight more technology then a box with a metal or platic plate and a spring under it, but again stuff that seriously predates electronic devices and qualify as 'oh duh' technology like the paper clip or stapler, once someone shows you one, you slap your forehead and can't believe you didn't think of it. Single column mags are the most widespread because they are cheap, simple, most reliable and because switching out a magazine is quick. Also lower capacity is generally thought to make soldiers aim more, which is debatable.

I attach those little photos because I want to emphasize that even a a magazine is pretty simplistic and can be made at home. You can't pan springs, and you could make the plate and magazine body out of plastic, wood, whatever, anything fairly rigid. Now, taking existing magazines to increase their capacity is another story. Also not to be confused with taping magazines together 'jungle style'. Connecting two magazines together (I don't know the term beyond 'idiot style' ) is when you remove the base plate of one magazine and connect it to another... nobody does that unless theirs some law limiting normal magazine capacity because it's not the best way to do it, and just duct taping them together isn't very effective. There are clamp and other apparatus that make that more viable and thus would let you walk around carrying magazines with say, 10 rd capacity, then in 30 or 40 seconds assemble two or three or more of them together, some magazines are designed with this in mind, really no way you can ban 'decent engineering' so another thing most of us 'gun nuts' tend to laugh at.

Anyway, more than anyone probably wanted to know but I felt this was a better reply than repeating talking points everyone's heard a hundred times. If you've got a few thousand dollars lying around and have some mechanical aptitude, you can manufacture your own machine gun, including the bullets, without ever ordering anything gun related or any suspicious quantities of anything. You can't ban chemistry or engineering, and when we say gunsmithing is hard, what we mean is that stuff like making your own match grade ammo is hard - bullets don't fly in straight lines, so the exact amount of powder must be used on the exact same amount of bullet for sniper accuracy. If you're just attempting to unload a thousand rounds of ammo into a crowded room, nothing complex. Of course, no one designs around that concept because a pipe bomb is considerably more effective and easier to build, and so is a mortar, that's why organized terrorist groups use those.

So that's the basics, I'm obviously not in favor of control but I'm content to have intelligent debate on it, but you can't have intelligent debate without knowledge, and hopefully that typically Isaac-long piece above gave you some without boring you to tears