SpudFiles

I still prefer the idea of blow-forward than blow-back, somewhat inspired by clide's GB semi I came up with the following, note that the spring is a tension one.

*update* I'm making a prototype of the attached design, should be done by tomorrow. I figure that even if it doesnt work as full auto with a constant flow, it will be a better blow forward valve than the subject of this thread due to less dead space and reduced friction since there aren't any epoxy pistons involved, just tight fitting metal-to-metal tubing.

Here's the prototype curing, it'll probably be ready for testing in a few hours.

Have you tested it yet?

How does it work?

*types quietly* Shhh... the lady's still asleep in my bed, I can't fire up the compressor just yet. Will give you the results in a few hours.

IT WORKS! IT WORKS!!! FULL AUTO BABY YEAH!!!

*ahem*

yes er, it works. at least the reciprocating bolt does, it cycles full auto with a constant flow of air. I haven'te tried it with ammunition yet, frankly the bolt cycles so quickly that I don't know if gravity feed will cut it.

anyway, in my enthusiasm, the hook holding the spring to the bolt came loose (and out came the bolt flying out of the barrel lolol) so a bit of epoxying is in order, videos to be posted soon

yay!

Nice one! Thats really awesome. I cant wait to see it in action.
If the gravity feed is too slow, will you use a spring loaded magazine, or just try slow the mechanism down a bit?
Good work on the lady too

Amazing Jack!


You never cease to amaze me.



I'm curious, what does your gf think about your hobby?

spud yeti wrote:If the gravity feed is too slow, will you use a spring loaded magazine, or just try slow the mechanism down a bit?

I'd rather keep it gravity fed, I'll try with a stiffer spring if it doesn't feed.

I'm curious, what does your gf think about your hobby?

She thinks I'm a 24 year old boy playing with toys, but at least she appreciates the mechanical ingeniuity and level of craftsmanship that are needed to exploit this hobby Besides, she occasionally benefits from my handiness with epoxy too

I really should allow the epoxy time to cure but I can't be bothered, videos coming up soon, watch this space

Jack, I'm pretty sure you can dramatically speed up the cure time of that epoxy with heat without weakening it. Most Epoxies actually benefit from heat curing.

I leave curing epoxy outside in the sun, in summer it will harden in about 6 hours compared to at least 24 in the winter. One thing I have to be careful with is the araldite with which I use to set up the parts before pouring the epoxy - heat tends to soften it, it's not the first time I've gone out to check up on parts to find they came apart in a gooey mess.

Whoa! Freekin awesome, dude! At first I was like: "It's just a blow-forward, how the blazes does he think he's going to get auto-fire from it?" Took me a while to see how it worked.

It seems to me that if you run it with some ammo, the increased barrel pressure ought to slow the cycle down a bit, so maybe your grav-mag will still work. If not, you might try steel ammo and a magnet.

see it in action here

Jack: I have been viewing your work for some time now and have decided that you are one of the most intelligent and mechanically inclined members here.

I'm working on a pneumatic design that I would like to be semi-auto and would love permission to incorporate this design into mine.

Cheers for that, though I'm sure there's a lot more potential on this forum, if only people were more willing to move away from "standard" materials and be more adventurous in their experiments.

You don't need permission to use the design, honestly, have a look here and you'll see that there are hardly any original designs left anymore. The concept I used is essentially identical to this one in principle, just built a little differently.