I'm trying to explain to some friends of mine that civilian AR-15 style firearms cannot be "easily converted into machine guns." I know with the CETME you'd have to replace the bolt carrier, trigger group and housing and make modifications to the receiver - all of which require NFA clearance to own or do. Even just drilling the receiver is a felony.

Can anyone point me to the broad strokes of what is involved in converting an AR? I don't need details or a howto, just the steps involved so I can explain why its not just plug and play. Though, as an amateur gunsmith I'm curious about the details.

I tried Google searching and it turned up so much flack that I figured I'd ask here.

I think we should be able to have full-auto weapons.  I think the pro-gun groups are making a mistake stressing the point of auto versus semi-auto.  They need to make a stronger point of good gun owners versus bad gun owners.

They'll probably bring up how easy it is for mass murderers to bump fire their ARs and kill dozens of people that way.

Not sure if it matters anyways, in the Army we rarely ever use burst mode on our M16's.  Always use semi-auto for training.  See the irony?

While I agree, I can't make that argument to my friend who is terrified of machine guns for some reason. 

I would not openly search for those types of things. They are most definately monitored.  Basic difference is a more heavy duty bolt, and an auto sear that enables the hammer to not be locked back. Remember Hawaii is not a class 3 state.

step 1 - sell it
step 2 - move to state that allows
step 3 - get ready to spend bucketloads of money and wait for day that may never come
step 4 - wake up from dreamworld and continue fight to retain what rights we have

Sears get plenty hammers!  All kinds!  Buy before the ban on hammers!

I believe this topic should not be discussed on a public forum, regardless of the context.

I believe this topic should not be discussed on a public forum, regardless of the context.

+1 

no one cares.  arfcom has an article that's been pinned for years.  basically, you need a new trigger assembly, the sear, and the bolt carriers are designed so that even if you threw a civilain ar 15 bolt into an M16, it wouldnt trip the auto sear.  and i believe civilain lowers are machined in such a way that adding the full auto trigger group is impossible without further machining. 

so thats at least two parts (the lower and the bolt carrier) that would need either heavy machining to convert, to be replaced with NFA registered parts, along with obtaining the sear and stuff.

basically, you'd need to replace everything but the upper and barrel.

http://www.ar15.com/content/legal/AR15-M16Parts/

Most people seem to think that you can just file/remove some parts and make it full auto.  That might work if your bolt was able to outrun the hammer and lock up before the hammer hit the primer, but in practice what's going to happen is that the hammer is going to strike the primer before the bolt is in battery and blow the gun up in your face.  Or at least that's my amatuer gunsmith's understanding of the problem.  A full auto fire control group keeps the hammer from falling before the bolt locks up, which is necessary for an AR.  Anything that doesn't fire from an open bolt (which is pretty much every modern firearm) would require extensive gunsmithing knowledge and parts manufacturing.

Most people seem to think that you can just file/remove some parts and make it full auto.  That might work if your bolt was able to outrun the hammer and lock up before the hammer hit the primer, but in practice what's going to happen is that the hammer is going to strike the primer before the bolt is in battery and blow the gun up in your face.  Or at least that's my amatuer gunsmith's understanding of the problem.  A full auto fire control group keeps the hammer from falling before the bolt locks up, which is necessary for an AR.  Anything that doesn't fire from an open bolt (which is pretty much every modern firearm) would require extensive gunsmithing knowledge and parts manufacturing.

the hammer would just whiff, wouldnt it?  if the bolt wasnt in battery, the hammer would hit nothing right, because its designed to strike the firing pin on the bolt?

the hammer would just whiff, wouldnt it?  if the bolt wasnt in battery, the hammer would hit nothing right, because its designed to strike the firing pin on the bolt?

Hmmm.  Maybe so.     I guess it would depend on the geometry and I don't have an answer for that.

Without going into detail, you'll need to machine a lot of metal precisely, drill a certain hole just perfect, and find some very hard to find parts.

Truth.  Of course, why spend all the time, effort, and money to convert an AR to full-auto when any half-assed machine shop can find blueprints for a Sten gun online and crank them out for less than a Benjamin?

Hmmm.  Maybe so.     I guess it would depend on the geometry and I don't have an answer for that.

i'd imagine the bolt would get damaged closing on a hammer that's supposed to either be cocked or behind the bolt carrier.  Just thinking about it, such a set up would possibly fire one shot, then lock up entirely, needing disassembly to fix?

Hmmm.  Maybe so.     I guess it would depend on the geometry and I don't have an answer for that.

i'd imagine the bolt would get damaged closing on a hammer that's supposed to either be cocked or behind the bolt carrier.  Just thinking about it, such a set up would possibly fire one shot, then lock up entirely, needing disassembly to fix?

i'd imagine the bolt would get damaged closing on a hammer that's supposed to either be cocked or behind the bolt carrier.  Just thinking about it, such a set up would possibly fire one shot, then lock up entirely, needing disassembly to fix?

Dammit, now I'm going to have to go home and look.  I'm pretty sure the bolt retracts far enough for the hammer to come back up in front of it, although if it did jam up somehow like that you'd be in trouble because the bolt carrier would be partial into the buffer tube, so you'd have to work through the ejection port or maybe separate the upper and lower completely.

Dammit, now I'm going to have to go home and look.  I'm pretty sure the bolt retracts far enough for the hammer to come back up in front of it, although if it did jam up somehow like that you'd be in trouble because the bolt carrier would be partial into the buffer tube, so you'd have to work through the ejection port or maybe separate the upper and lower completely.

oh yeah.  You'd damn near junk the gun.

Thanks for the replies, all.

My buddy is from CA and doesn't quite buy my explanation that converting civilian firearms into NFA regulated "machine guns" is difficult. While I pointed out the de-milled parts of my rifle he just said "Yeah, but this isn't an AR."

Thanks for the details and the link, xer 21. Exactly what I was looking for. I like to know exactly what I'm talking about when I'm trying to make a point like this. My buddy will still certainly be anti-gun but I like to make sure anti-gunners have all the details they need to understand why the "solutions" their "side" is offering aren't really valid.

Thanks for the replies, all.

My buddy is from CA and doesn't quite buy my explanation that converting civilian firearms into NFA regulated "machine guns" is difficult. While I pointed out the de-milled parts of my rifle he just said "Yeah, but this isn't an AR."

If he is talking M1 Carbine being converted to M2 Select-Fire Carbine, your friend is most certainly correct. Not sure if your debate is AR specific or not but there is major differences.