Something that's been pissing me off lately, especially concerning the recent shootings in Oakland, is the old wives' tale that keeps being passed around like gospel that semi-automatics are easily converted to fully automatic. We hear the countless references to 'drop in conversion' kits you can buy right here on the Interweb Tubes (of course, sans an actual link that would show the kits and their availability). We're told that any yahoo with a Dremel and a #6 ball-peen hammer can take Granpa's bolt action 30.06 and turn it into a lead-belching, fully automatic machine of death.
Sorry, that's bullshit.
How easy would it be to convert a 5-speed stick shift into an automatic transmission? It can be done but it's not as easy as simply purchasing the new transmission and slapping it in. You have a different clutch system. The stick itself is completely different. Certain parts won't mate to the frame correctly and either require drilling or complex attachments to make them fit. Weaponry is the same.
Now, to be perfectly clear, I am talking about converting a firearm to automatic fire so that while the trigger is depressed it continues to fire. The key point is that when you release the trigger, it stops firing. To be fully automatic, you need to be able to control the firing sequence. Many firearms can be modified so that sometimes you can get more than one round per trigger pull. Hell, slam-firing sometimes happens on semi-autos without any modification, but that is not full auto.
In order for a firearm to repeatedly fire off rounds, there are all sorts of mechanical timings that have to happen for reliable feeding. Release the hammer too soon, it slides along the bolt as the bolt is closing and may not strike hard enough to cook off a round. Bolts or bolt carriers that aren't designed for that kind of stress may not function long enough to give you the results you want. Gas systems may not be able to bleed off fast enough. There's dozens of variables that need to be taken into consideration and simply replacing a pin isn't going to solve all of them.
It takes a machine shop to turn a firearm auto, not just a set of tools from Craftsman and a kit you got from the web. UPDATE – Ry illustrates that you can indeed get a Craftsman drill press and a kit off the Interweb Tubes and go full auto. From what I've been able to read and discern, while there are lowers that accept the kits easily, many of them still require milling to get things to work properly. So, while it's a bit easier to do than I wrote, it does not detract from the information that follows – full auto is pretty much useless as a hand held firing mode.
Yes, certain firearms can be made to fire repeatedly by filing down X, Y, and Z, but not with any regularity or safety. And a gun that shoots repeatedly when you only intend it to shoot once isn't something that's going to be accurate enough to hit the target before the muzzle decides to try to hit a cloud or the ceiling.
Which brings me to the next major point – I hope that if anyone ever does decide to take a shot at me that they do so with a fully automatic firearm.
In the Marines, the M16's we had had 3 modes : Safe – Single – Burst. Safe was no shootie, single was semi automatic (one trigger pull, one round) and burst gave three rounds before the seer would reset. Why would the military give their soldiers a firearm that only shot three rounds? Because hand held weaponry is not generally accurate in full auto firing mode. The recoil is additive and by the 3rd round, you're not generally on target. This is why most full auto firearms are either mounted or of a lower power round.
The other issue is that full auto goes through ammo like Obama goes through teleprompters. Well, maybe not that fast but considering a common 'high capacity' magazine holds 30 rounds and full auto fire can chuck out 650-700 rounds a minute, you're out of ammo in less than 3 seconds. Being that maybe the first round or two will be on target before the recoil throws you off, that's 28 rounds of 'noise' you just wasted.
What I was taught in the Marines, you used full auto for suppressive fire, not generally targeting moving items. By setting up a 'wall of lead' from a belt fed machine gun, people couldn't move past that line without being mowed down. You fixed your line of fire and then swept inwards to cause people to move into an area where people with semi's could pick them off.
When you mounted the firearm on a vehicle, you had something to absorb the recoil better and could aim just a bit more. Aircraft had even more systems that would electronically compensate for the recoil so that you could target moving items, but that type of assistance comes at a cost of weight, something the standard troop cannot carry on his back.
Full auto is a boogey man, used by the media and anti-rights bigots to 'scare the white people' into thinking that gangs are walking around carrying mini-guns, mowing down entire playgrounds like Rambo or the Terminator. You cannot convert a semi-automatic into a fully automatic any easier than you can switch a car from stick to auto transmission. It requires tools, skills, and quite a bit of work to do to make a machine that is reliable enough to do what you require.
Those who rig their guns to shoot repeatedly from time to time are not causing the amount of mayhem that requires such onerous laws that forbid civilians from owning machine guns made past 86 (as if one made in 87 would cause more problems or something). It's a lie meant to create an artificial market so that the ownership of real full autos becomes financially infeasible for the populous and nothing to do with public safety.