Ok /k/, I've drawn this gun idea. It's a single shot barrel, it mounts to an ar15 lower. The little two tabs on the bottom mate up nicely to the magwell on a lower. the breech cap is like on the RN-50 from serbu. This way it's easy to machine and simple to load and fire.
my biggest concern is since the upper will mate to the magwell, will the recoil hurt the lower in any way? like, with 308 or something.
>>30209691
Maybe attach it to the actual barrel somehow, that way the recoil is distributed more evenly
>>30209691
My only question is "Fucking why?" Why does it need to mount to an AR lower? Why not just make it fit an R700 stock or something common that makes more sense?
>>30209716
Why do we go to space? Why do we test new planes? Why do we come up with new stupid ideas? Sometimes they end up helpful
>>30209716
cause I want to and my design has a firing pin, I don't want to do a striker fired
>>30209716
if its big enough, used could use it as a flare/smoke launcher
>>30209745
good idea, I could make it fit flares no prob,
>>30209691
I would approach this with the original upper in mind. Maybe instead of just it being attached to the magwell, i would add more material so that it fits in the front takedown pin. That at least can take some of the stress from recoil, because I dont think the magwell itself is designed for impulses of force created by recoil.
>>30209945
^^
This. The recoil in the ar is supposed to go straight back into the buffer tube.
Do some more looking at those .50bmg single shot uppers.
Maybe make a sliding arty style breech?
>>30209758
Under mounted flares might be a neat thing.
>>30209945
>>30209989
I'm avoiding complexity at all costs. so far, no moving parts other than the firing pin. here's how it looks on a lower. this might help understanding a touch.
>>30210151
It should probably use the takedown pin as well for extra security
>>30210151
Are your tabs going to come down far enough to lock it in with the mag lock?
If no, then how is it held in place? Magic?
Also might as well add a small piece that will fit the front piviot pin, and a flat piece off the back to reach the rear take down pin. You'll need to cut a slot in it for the hammer to come through but it will also keep some bigger things from getting jammed in your completely exposed trigger design
>>30210219
>>30210222
I've considered all those items, and I could, but I want to make the machining process use as little material as possible so adding the takedown pin and covering the trigger group adds more material.
I need to draw a plate that has a screw in it, so it can pull the receiver bit down towards the lower. no magic here.
>>30210151
>>30210219
you can use both takedown pins. Run tiny struts to the rear takedown pin that the hammer can strike through to lock it down as well as a normal upper. doesn't have to actually use the pins, just the holes. If you want a quick disassembly you can just snap it in the back and lock it with a toggle
>>30210151
I would seriously add the front takedown pin and extend the tabs all the way down the magwell. The top part of the magwell is really thin and with those short tabs that area is going to be under amlost all the stress. And then you can also cut a slot for the mag catch to keep it in place even better like>>30210222 has mentioned. It may be more work, but its better to do it right than screwing up a lower.
>>30210258
80% lower is worth testing on, But that's why I'm here for ideas.
>>30210258
That makes me think. I can make a plate that has the holes for the takedown pins and mount the barrel holder to that.
>>30210254
>I need to draw a plate that has a screw in it, so it can pull the receiver bit down towards the lower. no magic here.
This sounds fine. If your concerned, extend the length of the tabs to give more area into the magwell to distribute the force. It would also be trivial to add a shelf that contacts in front of the magwell where the front takedown pin is, without actually using the takedown pin (no hole, just an additional contact shelf to distribute the force further). The setup to mil the bottom tabs already allows this, without needing the additional setup to drill the hole for the pin.
If you're truly going for simplicity, I would suggest slab sides and a bolt on rail rather than machined. The sunken in section around the breech thread isn't strictly speaking necessary (but you should add a gas relief hole in there) and it would be simpler if the barrel, trunnion, and breech cap used the same thread.
I think a problem with threaded breeches in general is that they seal up gases fairly well in an unsafe way in the event of a case head failure. They don't have a designed venting path like a bolt action that doesn't actually seal around the chamber. A gas relief hole in the breech cap would probably be a better idea than that sunken in overlapped section in the trunnion.
>>30210151
>>30210349
What stops someone from getting a "ar15 trigger jig/tester" like pic related with the pushpin setup just so you can mount these uppers?
You could potentially have an unregistered 5 shot magazine fed 50bmg shipped straight to your front door if you buy the right items.
>>30210960
the same thing that stops you from making full auto lutys from scrap metal, 10 years in federal rape me in the ass prison
>>30211035
You can legally make a .50 BMG rifle, with some states as exceptions.
>>30211115
i thought if the bore diameter was .50 or more the ATF could fuck your ass
>>30210610
gas relief hole I will add, slabsides is also not a bad suggestion, probly also going to extend the tabs a good bit.
My barrel is pressed in and theres a shoulder that it butts up to the trunion with, so the relief for the breach cap is somewhat artificial, not a design choice. there's just enough threading for the cap instead of threading the whole trunnion. front recoil lug is going to be added, that's a good call.
>>30211035
its the ATF's fault for not regulating upper receivers. They are legally not a firearm even though they can chamber and headspace a cartridge. You can set it off them off if you strike the firing pin.
The upper receiver on the scar platform is serialized like this.
>>30211127
just buy a real 50 upper and mount a shitty trigger jig on it
bullpup 50bmg
>>30211127
no it has to be exactly more than .50
>>30211127
Up to .50 inches you are fine. Or if you have the sole purpose of never selling the firearm and use it for "sporting purposes*"
*defined by the ruling attorney general
