Delayed blowback work in progress
Posted by Admirable_Scholar_36@reddit | GunnitRust | View on Reddit | 21 comments
Completely diy 9mm delayed blowback. I’m designing this to be made without a lathe or mill, printed jigs, and no existing gun parts. (First picture is of a printed mockup)
Charming-Two-7697@reddit
Still waiting
Admirable_Scholar_36@reddit (OP)
Graduated with degree and work at firearms company now, so been busy. I still intend to finish this design, but I have done some pretty serious redesigns on the delaying mechanism.
lawblawg@reddit
I've been toying around with ideas in this space as well. Definitely going to keep an eye on it.
Can you give more info on the delay mechanism? You describe it as being the same as the Savage A17 but I haven't been able to find much on that. The Savage Arms website discusses it but doesn't actually describe the operation. Do you have any diagrams? It it similar to the Rudd Arms delayed blowback AR180?
I've been playing around with DIY radially delayed blowback in a handgun platform. While the CMMG radial delay system obviously requires quite a bit of extremely high-precision machining, an "inside-out" version (where the radial bearing surface wraps around the outside of the barrel rather than fitting inside an AR-style barrel extension) is much simpler. Ideally the design I'm contemplating could be made with a hex bolt, a coupling nut, a few set screws, and a barrel liner, using nothing more than a Dremel and a drill and printed parts.
Admirable_Scholar_36@reddit (OP)
When I say it’s pretty much the a17 vertically traveling delaying wedge, it’s pretty much that. I’ll find a photo to send.
GunnitRust@reddit
https://old.reddit.com/r/GunnitRust/comments/1ftbuaj/summer_rust_2024_results_2024_complete_year/
cybernetic_Toaster4@reddit
Awesome! I won't lie I have been trying to find some kind of pipes to use for a barrel. Be it 22Lr, 9mm or maybe even 5.56. I don't know where to find the metal for it. Maybe it's the key words I'm looking up? Could use some help if thats okay. I have been wanting it design some 3-D stuff myself but I don't have a printer yet so also will take suggestions on that too 😅
Admirable_Scholar_36@reddit (OP)
I tend to use seamless hydraulic steel tube. I do my math assuming shougang quality steel lol.
cybernetic_Toaster4@reddit
Much appreciated there kind Scholar! ❤️
Beginning-Position-6@reddit
I recommend that you take all possible care...
I have dealt with 9x19mm blowback even with delay obtained by the friction of "5051 steel guides" on both sides of the bolt, and it still continued to be violent with a 340g bolt operating in a 30 cm upper space.
Use as much steel as possible... Sometimes the catastrophic failure does not happen in the first round, happen after 2 or 3 days of casually testing the weapon.
If your bolt weighs between 300 and 400g, I recommend making it an open-bolt (that's what I chose)...
Admirable_Scholar_36@reddit (OP)
I am a mechanical engineer, so I’ve done a bunch of calculations to ensure the delaying system will reduce the velocity of the bolt enough to get a safe chamber pressure for extraction. I will test it from a vise behind cover though, because I never fully trust my math until I’ve tested it in real life.
Admirable_Scholar_36@reddit (OP)
Yup. The upper is made from steel plate, only printed a model for size comparison.
Admirable_Scholar_36@reddit (OP)
It’s a delayed blowback system.
bmoarpirate@reddit
Printed jigs ftw
xabc1@reddit
All the congrats to you. That’s amazing. Good luck it’s really beautiful work so far.
Admirable_Scholar_36@reddit (OP)
Thanks!
shortbed454@reddit
Looking good bud. Love seeing the updates. What all do you have left to design?
Admirable_Scholar_36@reddit (OP)
My main focus is to finish up how the spring and buffer will be constructed, and then the lower frame. I have a few ideas for the internal hammer, and it'll just borrow the mag well and release from a glock.
shortbed454@reddit
Right on. Keep up the good work. I know there's quite a few of us who are looking forward to seeing it.
Admirable_Scholar_36@reddit (OP)
Thanks!
LostPrimer@reddit
What delays it?
Admirable_Scholar_36@reddit (OP)
Linear wedge with angled surface. After designing it I found it’s essentially the exact system the savage a17 uses lol.