Some of the even more modern ones aren’t much better. A family member owns a full-auto MAC-10 and several of us got to shoot it a few years back, including my grandfather (an Army veteran and deer hunter for over 40 years), my father (a police officer and member of his department’s competitive shooting team) and me (Expert Marksman with both the rifle and pistol in the Navy).
We fired ~300 rounds at a 6"x6" wooden block at ranges from 30-50 yards and it escaped unscathed.
Probably one of the strangest, yet most fun events of my life was when a good friend of mine was on the West Point faculty, and invited my wife and I to their annual Historical Weapons Shoot. Basically the cadets go through by company and get familiarized with the weapons, and in the intervals between companies, us civilians could shoot the weapons (with Army officers supervising and helping).
So basically we got to shoot the following weapons:
[ul]
[li]MG-3 (7.62 NATO version of the WWII MG-42)[/li][li]Browning M1919A6[/li][li]BAR[/li][li]FN-FAL[/li][li]AK-101 (for ease of getting ammo)[/li][li]M-14[/li][li]M1 Garand[/li][li]M1 Carbine[/li][li]STEN gun[/li][li]MP-40[/li][li]M3 Grease Gun[/li][li]Dragunov sniper rifle (kicks like a f**ing mule)[/li][/ul]
Most of them were semi-auto, but the machine guns and submachine guns were short-loaded with like 5-10 rounds or 20 rd belts.
Machinist here. Yes very basic lathe that could do all those things EXCEPT rifle the barrel. That is done on specialized machine tools. A standard lathe isn’t set-up to cut grooves with that kind of pitch. I guess if one was really desperate , it might be possible to convert a lathe to do rifling.
Cool.
ETA: moldmonkey, what’s your take?
Wow… making still parts (that copper tubing stuff) and gun barrels. Interesting hobbies.
Well yeah, but the purpose of these weapons is/was to put as much lead in the air in as little time as possible, accuracy a distinct second priority. Multiply by a squad and something is making its way into someone, somewhere 
; or at the very least keeps their heads right the hell down. And it’s just what the doctor ordered to clear a trench, a hallway or a bunker, whereas a bolt action rifle ? Not so much.
Rifling is not that difficult. Early rifle makers used a wooden screw driven by hand for rifling. It looked like pretty long barrels could be rifled in an hour or two that way. The same kind of long tool bar and alignment within the barrel is needed as for boring, which is needed whether or not you start with a piece of pipe. A modern lathe should be convertible to a rifling and boring machine. Based on what’s said above maybe rifling doesn’t matter much for a machine gun, and maybe it’s a problem to use ammo with a tight enough fit to spin well because of jamming.
If you load from the breech, you don’t have to worry much about the bullet not going through the barrel. Smokeless powder will develop 1000 to 4000 atmospheres. Does anyone know what kind of pressure black powder will produce?
As for redneck rifling, it looks like something simple can be worked out although I don’t know how good a job it does of stabilization the bullet: Homemade barrel rifling machine, rifling the Kolt380 barrel - YouTube
August West, were you firing in bursts of 3-10 rounds or just going full auto until the magazine runs out?
I’m assuming that you had the stock open and the weapon at your shoulder, aiming through the sights, short bursts? Because if so, damn.
That’s the same guy as the link I posted - looks like he’s got a few different videos of modifications.
Wouldn’t black powder foul up an automatic weapon pretty quickly?
Simple rifling doesn’t need a lot of accuracy in the machining. He’s doing a very short barrel there, not that hard to keep the tool aligned. I don’t know what the ideal cut, number of turns and other real gunsmith’s details would be for good rifling, but the machining should be sufficient with that device to compare to the best tools for simple rifling.
Just got a chance to watch the video. My first take is I would never ever fire a weapon this guy has worked on. I suppose what he has done would work to some degree but the crudeness of it would effect accuracy.
Rifling is basically shallow multi-start threads with a very large pitch. (The large pitch is why you can’t rifle on a basic lathe). The way he wrapped the rod wouldn’t give a very consistent helix so the rate of spin would be increasing or decreasing.
The way he indexed to get the next grooves doesn’t allow for them to be in sync very accurately. Think sine waves wrapped around a cylinder. You want the peaks and lows of each sine wave to be at the same distance from the end of the cylinder as each of the other sine waves. You also want each sine wave to equidistant from each other around the circumference.
I would think his rifling grooves would be “fighting” each other as the bullet travels down the barrel.
Also I’m wary of what grade of steel he used for the barrel that he was able to cut the rifling with such crude tooling.
As far as the OP, for a spray and pray machine pistol of this design is just fine as a smooth bore. If I was in their place and wanted something more accurate, I would use that lathe to modify AK47 parts and skip trying to rifle my own barrel.
I didn’t watch the whole video but he would have to get his indexing right, and if the pitch wasn’t consistent he’d probably cross his cuts at some point. But a lot of early rifles were done with some pretty simple tools. Here’s a picture of an early rifling machine (clearly a reproduction). The grooves were cut one at a time with the cutter depth adjusted on each stroke.
It would have to pretty bad on such a short barrel and I wouldn’t think it takes much to cause problems. I’ve never done rifling but I have done multi-start threads and it takes very small errors to cause issues with binding. Granted explosively pushing a soft lead bullet down a barrel overcomes some of that but it will effect the spin given to the bullet.
What he did probably works but it’s a lot of work to get very crude results. I have been poking around the machining related internet since before Practical Machinist came around and have seen a lot of DYI machines and have built some of my own. In my experience, many of these guys are much more interested being able to say they built such and such machine than on if the results are accurate or practical.
I can’t see your link at work but have seen early rifling machines and they are much more sophisticated than this guys deal…
It was quite a few years ago, but as I remember it we first fired from the hip and then switched to firing from the shoulder with the stock extended because we were stunned that we couldn’t hit anything!
Short bursts are difficult with the MAC-10 because the rate of fire is incredible. We were loading 25 rounds into each magazine and it would empty the magazine in less than 2 seconds.
Black powder produces much lower pressures, so probably about half that.
If you use the same amount of smokeless powder as you would black powder in a gun that is designed for black powder, you’ll blow the gun up.
I would think so.
The P-45 Liberator pistol seems germane to this discussion - they were made in large quantities for about about $2.50 each during WWII and dropped to resistance groups; the idea was they’d be used to shoot an enemy soldier and then the firer would take their gun.
There’s not a lot of evidence they were ever actually used for their intended purpose, though.
It rules out gas impingement. I’m not sure about blowback of the straight or delayed kind.
I suppose very good black powder mixtures can be made (and I’m not sure why we’re discussing it because there doesn’t seem to be a shortage of other explosive materials to use), but I have the impression, perhaps mistaken, that black powder is dirty, leaving a lot of residue behind. An automatic weapon needs a loading system of some kind and I’d think that would fail easily using a dirty powder. I’d think it would also clog up simple rifling and the bullets wouldn’t spin. Maybe polygonal rifling wouldn’t be a problem but I’m guessing it’s more difficult to manufacture a barrel that way. Now if black powder is clean enough then it shouldn’t be so big a concern, but as mentioned above, it has to be just as clean as the alternatives using a larger amount of powder.
Black powder is indeed dirty and leaves a significant residue which forecloses some designs. The main US civil war guns were black powder rifles and the bullets seem to have spun (otherwise there was no point in using them over smoothbore muskets). The original Gatling gun used black powder and worked. Perhaps a blowback system could replace the handcrank.
The loading system could not be as complex or compact as what is typically used in modern assault rifles and machineguns, that’s true.
You mention other materials to be used as propellants. Which ones are you thinking about that could be made by amateurs with the same means and in the same set of circumstances that would compel them to use jury-rigged weapons like the Carlo? They could use factory-made ammo but I’ll reiterate my puzzlement at someone in the Middle-East/war zone having access to 7.62x39 ammo but not an AK.
