AR-15 sheet metal and tube upper receiver
- Thread starter justin22885
- Start date
- Status
Kp321
Member
If you configure it for a reciprocating bolt handle, the complication of the charging handle track would be eliminated.
justin22885
member
- Joined
- Nov 9, 2009
- Messages
- 2,102
well, the AR-15 upper design i made in a couple hours, including a previous failed attempt where i was trying to use only sheet metal, so i can bang stuff out on inventor pretty quick myself
the sheet metal for the exterior of the receiver is thick enough that the track for the charging handle can be cut in the sheet metal and you still have a good 1/32" thickness between the inside of the track and the outside of the receiver
justin22885
member
- Joined
- Nov 9, 2009
- Messages
- 2,102
doing this project has actually given me some good ideas for how i can simplify the FG-42 receiver design as well, now being able to make an outter shell of sheet metal fitted with an interior tube piece for rails for the carrier to ride on, plus a trunnion i can basically sketch out a simplified FG-42 as well later on.. so the type of receiver i made could be scaled to different weapons
MachIVshooter
Member
Have you ever tried to cut large diameter fine threads without a lathe? Ain't easy to get them straight. At all. Cutting threads on the front of a receiver is not even in the same ballpark as increasing the threaded portion of a bolt shank or tapping a few 3/8 course thread holes in some mild steel plate to attach a bracket or somesuch. A couple degrees off doesn't matter in those applications, but it certainly does for a receiver nut or buffer tube. Getting such threads true enough with a conventional die would be quite difficult indeed. As well, a quality adjustable die for thread cutting is going to cost you twice what a forged flat top upper would, not to mention the die wrench.
I understand what you're trying to do with some of your ideas, and it's a worthy venture, but truthfully, you need to spend some time at the work bench rather than the computer screen to gain a better understanding of what is feasible and what isn't. Designs that seem relatively simple on paper are often anything but when it comes time to turn blueprints into 3-dimensional mechanical parts. That's why serious firms have design teams, which include the think tank folks, the engineers, the bean counters, and finally people with a background in the relevant manufacturing field. Together, they come up with something practical and workable that none of them would do nearly as well on their own. Designers & Engineers are relatively notorious for designing machine parts that cannot be machined. CAD often helps with that, but the degree to which that is true depends on the program and the ability of the designer to use it properly. Even at that, plenty of blueprints go back to the drawing board because though theoretically practical to manufacture, it turns out to not be in the real world.
justin22885
member
- Joined
- Nov 9, 2009
- Messages
- 2,102
never said it was easy, just said it was possible
MachIVshooter
Member
Of course it's possible, but it doesn't really fit the constraints of:
If you take away the simple/expedient aspect, then it has to do something existing versions do not to be practical. Where the AR is concerned, there is absolutely no reason for steel receiver halves. As you know, I've machined them, but for fun and because I wanted to say I have a carbon steel AR lower. Turnbul manufacturing and Cobb have as well. But aside from being able to color case harden or deep blue, there is absolutely zero advantage to steel in this application, and plenty of disadvantages. My billet steel lower weighs 3 times what a standard 7075-T6 forged unit does, and the strength is completely unnecessary. The same is true of the upper; there are plenty of ARs out there well into the 6 figure round count with no appreciable wear to the upper receiver, which can be had for $40-$50 all day long, and sometimes less (I paid $29 for an anodized forged flat top upper from TM earlier this year) if it ever needs replaced.
Again, I do not mean to discourage, but if you are unable to deal with constructive criticism, even to the minimal degree of pointing out how difficult it is to cut true threads with a hand held die wrench, then maybe you should refrain from putting your ideas out to be scrutinized until you've proven the feasibility.
R.W.Dale
Member
Our non overtime rate is $90 an hour and the machine shop has a 2hour billing minimum
thats just Your shop...
i know of at least half a dozen quality shops where i could get this done for <$50.....have the shop run it as a low priority job.....maybe have several done at the same time......not a problem.
rcmodel
Member in memoriam
Apparently you haven't priced a steel injection mold die complicated enough to produce such a thing.
It would take longer then the useful life of the mold to even come close to breaking even.
This looks like another Ingenious Solution to a Non-Existent Problem to me.
rc
MachIVshooter
Member
Assuming they have that tap. Otherwise, you're looking at buying that first, or paying them for the time it takes to make a fixture that allows lathe cutting the threads. I suppose you could have it done before you attach the sheet metal to where the tube could simply be put in a chuck or collet, but that presents some other challenges, not the least of which is that you've gone from a $5 piece of DOM or seamless tube to a relatively expensive machined part, so any errors from that point which make the piece unsalvageable have a much higher price tag.
Besides which, even if you could get it done for 1/3 that price, you lose the OP's purported benefit of
when there are gobs of $40-$50 finished stripped uppers on the market.
Also, RC model is 100% correct about the other proposed approach when he points out
That mold would easily be $30,000. The man I bought my lathe and mill from was a mold maker, did steel and aluminum injection molding dies. The one for a flip top lotion container was a $17,000 die, and he also charged the customer $0.53/unit for molding. The containers sold for $1. You do the math on how many to amortize the costs before it started turning a profit.
for your average DIYer.....of course Plastic injection molding is out of the question.....but 3D printing is common, cheap, and effective
R.W.Dale
Member
3d printing is absolutely NONE of those things.
I'm thinking you don't spend much time in shops
I'm thinking you don't spend much time in shops
justin22885
member
- Joined
- Nov 9, 2009
- Messages
- 2,102
the uppers you buy are only cheap because they are made in such high quantities its almost ridiculous to think about, if any legislation was passed and those factories were churning them out like they are now, prices would rapidly go up.. theyre not simple to machine but they have a plethora of specialized equipment to do it quickly in high numbers
so theyre only cheap right now because theres so many being produced... take the AK rifles for example, a few years ago they were a few hundred bucks because the parts were economically available because they were being produced at such high quantities overseas, but with those starting to dry up you now see that same quality AK costing you about $800
dont confuse whats easiest and cheapest to buy with whats easiest and cheapest to make
so theyre only cheap right now because theres so many being produced... take the AK rifles for example, a few years ago they were a few hundred bucks because the parts were economically available because they were being produced at such high quantities overseas, but with those starting to dry up you now see that same quality AK costing you about $800
dont confuse whats easiest and cheapest to buy with whats easiest and cheapest to make
Im a Mechanical design engineer......i do this for a living......
a 3D printer IS all of those things......a quality printer can be had for <$1000......and can produce fully functional parts that are ready for use.
ive personally printed full and usable rifle stocks out of PLA.
3D printing has come a long way in the past few years
justin22885
member
- Joined
- Nov 9, 2009
- Messages
- 2,102
3D printing still has a long ways to go before its viable for structural components or components that may end up taking a beating.. its fine if you want to make a mould to make something else out of fiberglass (like 3D printing a car body panel you can use to make a fiberglass component from) or making temporary moulds out of wax, but you cant just push a button on a 3D printer and have a realistic firearm, not yet anyway
if someones going to invest in specialized equipment like a 3D printer, you could get a grizzly G0704 for about the same price and make real parts
if someones going to invest in specialized equipment like a 3D printer, you could get a grizzly G0704 for about the same price and make real parts
3d print a full firearm?....no......but 3D print a polymer housing to encase a metal dust cover.....absolutely.
and sure.....i would almost always recommend milling over 3d printing......but to your average person whos never milled before....it could seem a little daunting especially if you dont have anyone to teach you.....not saying you cant learn.....but learning 3D printing on your own is a lot easier than learning to mill on your own.
justin22885
member
- Joined
- Nov 9, 2009
- Messages
- 2,102
well, to the average person wanting a weapon that doesnt require all this equipment to make, the first step is to quit thinking AR-15, or AK, understand these weapons are made in factories, they have the backing of the industrial complex of entire nations behind them, the average joe clearly does not
so the absolute first step to a simple weapon that can be made economically is a completely different weapon design like the nearly complete weapon i posted an exterior rendering off on the first page.. or look at the AR-18 as another example of a better direction for economically viable small shop produced semi automatic rifles, and quite frankly i think you could do better, theres ways to improve the idea and youre not really going to 3D print anything on that because how do you get simpler than a roughly 1.5x1.5 inch piece of square steel tubing?
so the absolute first step to a simple weapon that can be made economically is a completely different weapon design like the nearly complete weapon i posted an exterior rendering off on the first page.. or look at the AR-18 as another example of a better direction for economically viable small shop produced semi automatic rifles, and quite frankly i think you could do better, theres ways to improve the idea and youre not really going to 3D print anything on that because how do you get simpler than a roughly 1.5x1.5 inch piece of square steel tubing?
MachIVshooter
Member
It's called economy of scale
https://en.wikipedia.org/wiki/Economies_of_scale
And, the situation being what it is, that's not gonna change any time soon. The upper is just a machined part anyway; legislation banning ARs (highly unlikely in and of itself) would control the lowers, not the uppers. That's why 80% lowers are so popular.
Preaching to the choir, bud.
The printer DefCad (Cody Wilson) was using to make receivers that still proved too weak without substantial changes and additional bulk was a $60K machine. You're not gonna turn out usable polymer AR uppers on a $1K Robo 3D or Dremel Idea Builder.
The prices are dropping, but we're still a ways from homeowner grade machines being able to produce high strength parts that even come close to what can be done with injection molded parts. At this time, a good used vertical knee mill is still the most economical way to make strong parts with complex shapes.
If you're thinking about a mill, I'd advise you to get the largest unit you can fit in your workshop/garage. You'd be utterly disappointed with the constraints of the small machines, including "medium sized" units like the Jet JMD-15. You can certainly make some things on them, but there have been times I've needed almost all of the knee travel on my Lagun FTV-2 to deal with a relatively small part, because that part had to be mounted on fixture, which was in turn mounted to my rotary table, and then I needed to be able to plunge a 6" LOC end mill 8" deep.
Bingo.
Something more along the lines of the M3 or Sten.
justin22885
member
- Joined
- Nov 9, 2009
- Messages
- 2,102
M3s and stens are nice and simple, but youre only going to get pistol calibers out of them.. i did design a new bolt carrier that takes the HK G3 bolt, locking wedge, rollers, trunnion, and barrel but unlike the G3/HK91, this all fits in a 1.5" round steel tube, kind of like a .308 cal sten .. unfortunately the average joe wouldnt be able to make the carrier.. i even posted the 3D CAD files for this delayed-blowback tube gun carrier on grabcad
.. unfortunately the average joe wouldnt be able to make the carrier.. i even posted the 3D CAD files for this delayed-blowback tube gun carrier on grabcadclearcut
Member
It could be a AKAR15 (come on some one had to say it)
CC
CC
MachIVshooter
Member
Correct. But that doesn't mean you can't take from their simplicity and build something that handles high pressure cartridges.
You should examine some of the Browning and Pedersen recoil designs. Those would be much more suitable for adaptation to expedient designs than rotating bolt gas operated or roller delayed blowback rifles. Remember, a lot of them were built in a small home shop in the beginning!
justin22885
member
- Joined
- Nov 9, 2009
- Messages
- 2,102
heres something i designed recently, the trunnion is just a round piece of steel bar with some grooves cut into the outside of the body of the trunnion to allow passage of gas through the trunnion and into the receiver to impinge on the bolt carrier.. theres a 1/4" lip on the front of the bolt carrier and a matching groove on the back of the trunnion so that the carrier will travel 1/4" before pressure is lost out the ejection port.. on the barrel theres merely a block to prevent gasses from pushing forward as the gasses fill the space between the barrel and receiver tube
the amount of space between the receiver tube and the barrel and the location the barrel is drilled will determine how long it takes for enough gasses to fill this space before it begins to move the bolt carrier rearward, so the volume of this cavity would be used to time the action.. this would make very a very simple, expedient, compact direct impinged system.. so much so the version in the second picture is actually a 9mm pistol barrel that would be pressed and pinned into the frame of a pistol ;-) hows that for a "sten-like" rifle?
the amount of space between the receiver tube and the barrel and the location the barrel is drilled will determine how long it takes for enough gasses to fill this space before it begins to move the bolt carrier rearward, so the volume of this cavity would be used to time the action.. this would make very a very simple, expedient, compact direct impinged system.. so much so the version in the second picture is actually a 9mm pistol barrel that would be pressed and pinned into the frame of a pistol ;-) hows that for a "sten-like" rifle?
- Status
