Throwing around an idea in my head for an open source rifle chambered in 30 carbine. Want it to be partially 3D printed and hardware store material. Don’t have much of a concrete design in mind, but i think it should take an FGC9 style lower with an m1 carbine magazine well and AR FCG. Upper would be held to the lower with ar-style push pins. Debating between round pipe or rectangular for the receiver. Straight blowback would have course be the simplest way forward for an action style. Any other ideas on how to proceed?
>>64616177last ditch and improvised rifles sound cool but if you're preparing for social collapse you're better of just buying a containerful of 11.5 inch PSA rifles. Higher quality, less work, and you don't have to pay for (low volume) assembly and construction.
>>64616187>Sound coolYeah, that’s why I’m doing this. Why else would I be making an open source design in 30 carbine? Because I’m preparing for the apocalypse? Of course not! I’m doing this because I can’t find any other designs like it and I want to develop some basic engineering skills.
>>64616200Anyway, I feel like modifying an existing design would be easier, but my experience with CAD is basically a single class I took in high school, so I’m kind of wandering in the wilderness looking for a starting point.
>>64616177>.30 Carbine>blowbackIt will suck, because making the bolt heavy enough to actually work with that cartridge is going to make that gun about as heavy and bulky as a battle rifle.You should REALLY consider some sort of delaying function for the action if you're dead set on not having a locked breech. It'll be more complex to achieve, but the gun could then actually be reasonably light with the cartridge you're doing, and it would also be much cooler.Now, magazines is another matter. You could roll with regular M1 Carbine mags, and they'll probably mostly work, but they were always pretty poor mags, GIs made sure to scrap them after using them a few times and then get new ones.If you wanted to go the extra mile, then working out your own mag would multiply your cool points by 10x.
>>64616240I considered a lever or roller delayed design, but I’m just not sure how to make it “hardware store” simple in regard to materials. I mean, don’t those kind of delaying components require heat treating?
>>64616177Square tubing is easier to DIY into a receiver, for .30 carbine you will need some kind of a locking system to prevent it from being ridiculously long. Look at the rogue 9 with all its jigs to machine a bolt out of. I have no idea if delayed blowback or a short stroke tilting block would be easier to design. Any kind of rotating bolt would be difficult to DIY and long stroke would probably require welding.
>>64616177>Any other ideas on how to proceed?Learn to walk before you try to run.
>>64616240Would gas blowback be an option? It seemed to just barely work for the 8mm Kurz and 30 carbine is even less powerful than that.
>>64616262Forgot pic rel.
>>64616260I’m just working on whatever harebrained ideas come to me in my dreams. I get the basic operating concepts behind these designs, I just don’t know the manufacturing side of things.
>>64616259Just doing a cursory search it looks like chamber ring delay was used for .30 carbine and could be created using ecm. Hesitation lock would also probably be more DIY friendly.
>>64616177Been thinking about trying a gas delayed rifle. That or a pump action revolving cylinder one, diy barrel is the trickiest part but there may be some options with nesting pipe.
>>64616274>I get the basic operating concepts behind these designs,I don't think you do, otherwise you'd have realized how impractically heavy the bolt would need to be to make a straight-blowback .30 carbine.>I just don’t know the manufacturing side of things.I'm suggesting more basic projects to learn that first before you attempt something as complex as a gun.Anyway, the good news is that there's tons of good resources on gun design you can read for free. Go read The Gun and Its Development by W. W. Greener and then The Machine Gun by Chinn. Small Arms Designs and Ballistics by Whelen is worth reading too, though you may have to track down a hardcopy of that.You don't need fancy tools to build guns, start with the basics.
>>64616339This is another good resource, and a stealth one at that. It's written with aircraft and race car builders in mind, but the techniques described are useful for building anything out of sheet metal.
>>64616339Maybe start out with something smaller, then? See how well I can put together each individual unit before trying my hand at one big project. Downscale it to 45 instead, perhaps?
>>64616339Heavy but not infeasible, there's even photographic evidence of a blow back .50bmg out there.
>>64616177Have you made an fgc9 to get a loose idea of what's involved? I suggest a nutty9 and then having a look at the other hybrid options at the gatalog.
>>64617111Tinkered with 3D printers in high school. Finally getting my own in tomorrow. Already got some filament and a temp box for when I start doing prints in nylon. Looking at the nutty 9, it’s a neat design. Never thought of using nuts to make a bolt, but it makes sense.
>>64616339I know it would be a heavy bitch. Around 3 pounds alone has to go to the bolt itself if my calculations are right. Still, if the basic concept behind the design is a simple rifle that can be cheaply made, then weight is something that can be added for the sake of manufacturing simplicity. As a previous anon noted, I could go with an ECM’d chamber ring delay, but I’ll cross that bridge when I get a general form factor down.
>>64617316Good luck, I'd suggest starting in .380 though and scaling up, much easier than building some fuckhuge blowback and needing to reengineer the whole thing into a delayed blowback. Hesitation lock is the most interesting to DIY imo, a lot of the shaping could be accomplished with an angle grinder and files and case hardening wouldn't be hard. One thing I remember from my weaponeer days is that doing bolt and receiver in mild steel while you're prototyping is nice because it lets you monitor deformation rather than hardened steel which tends to fail catastrophically.
>>64616281That's the Kimball pistol that you're thinking of, and that chamber ring did barely fuckall to delay the slide. That kind of thing can at most only be used to widen margins for locked breech actions.
>>64616426>there's even photographic evidence of a blow back .50bmg out there.There is zero evidence that it actually functions and isn't just a big pipebomb.
>>64617572Good to know, hence why I qualified with >a cursory google search. I'll revert back to hesitation delay looking like the easiest DIY locked breach. All this talk makes me want to go out and buy some square tubing and bar stock.
>>64617589That's always possible, but I bet they put a few rounds through it before it wound up on a table.
>>64616187I'd take a FGC-9 over this garbage.
>>64616187The kit for the 11.5 psa was $300 + $50 for the stripped lower, the parts for the whole fgc9 were $50.
>>64616177A while back I started redesigning the VolkStubbGewehr to be safe and printable instead of looking vaguely like a K98, but I didn't get very far before I got bogged down with more pressing projects. I'll probably get back to it some time this spring.
Has anyone gone to the Lassen community college for gunsmithing?
>>64617756Just discovered the RBC-9. It’s a belt fed 9mm designed to look like an m240b, but the interesting part is that it’s roller delayed. Used standard magcraft magnets as rollers. Wonder if that design could be scaled up to fire more powerful rounds.
>>64617822What other projects are you working on?
>>64616177the table in this article might assist youhttps://10mmautocombat.wordpress.com/blowback-bolt-calculations/As well as this compendium of resourceshttps://zco.world/firearms-design-resources/
>>64619270Building a house. Nothing /k/ related, I haven't had time for hobbies other than shitposting in a while.
>>64617765Look at that complete death trap, I would only fire it with a string from behind a tree.
>>64618705Are the magnets expected to operate on their magnetism, or is them being magnets just incidental to them fitting?People have tried to do magnetic delayed blowback for 3D printed guns, but it doesn't really work, what it always ends up doing is make the parts just run up against each other and cause friction, which DOES delay things, but it also makes those parts grind away at each other, so it's not very sustainable.
>>64624655The magnets have nothing to do with the delay operation. He used them to eliminate bolt bounce.
>>64618705>>64624736I've been thinking about a system that uses a magnet inside an aluminum receiver to delay the bolt cycling with eddy currents, which should allow the use of FRTs in ban states because it actually reduces the ROF even with an untrained shooter.
>>64616177.30 carbine would benefit from a simple locking system, thats what they did here https://en.wikipedia.org/wiki/Crist%C3%B3bal_Carbineprobably your best compromise between simple and not sucking if 30 carbines your choice of caliber
>>64617822Did you upload the files?
>>64625101I'll probably post test files here along the way, but I was serious when I said I wasn't far. I'm maybe 25% done with the receiver and I haven't started on anything else. I'm stealing some of the dimensions from the original design, but nothing will interchange. The only part that I don't know for a fact I have to change is the sear.
