75SD 3/4" hybrid with integral suppressor

[jackssmirkingrevenge]

As this has gone beyond a mini, I figured it was worth a new thread.



This is the biggest hybrid I've made to date, nothing particular about the design compared to the rest of the family expect the dimensions. It does however have a large drainpipe suppressor, which is quite effective:

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This is a test at 9x, fired at a box packed with old clothes and cushions. Most of the noise is due to the CO₂ capsule projectile going straight through the box and ricocheting off the backstop it's still evident something significant has happened when you click that ignitor, but the sound is extremely reasonable, especially compared to my previous 3/4" effort.

The muzzle energy is also up significantly, clocked at 482 feet per second that's 240 ft/lbs, well over twice the muzzle energy from the smaller chamber and edging into 38 special territory.

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Computer power supply at 9x, unlike the smaller chamber at 12x that only went through one side, this time it punched straight through.

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Second computer supply shot again at 9x, this time it didn't penetrate fully because it encountered substantial internal components visible in the damage picture.

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Third computer power supply shot at 1000 frames per second

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Mouse case, plywood, steel sheet, nothing seems to bother the projectile much...

Here's a full view of the thing:



Post-testing carnage:



Internal diagram:

[JDP12]

Awesome! Looks great! Any plans to make this into a pistol or shotgun configuration?

[Fnord]

I think this completes your initiation into the world of mid-size hybrids.
(Hooray!)

Do you plan to use the same high mixes that were in previous versions? The silencer sounds fairly effective judging by what little reverb your room has, though it may get pretty loud at 15x. I'd be interested to see what effect vents near the back end would have on your silencer(worst case you could always epoxy them shut again).

Awesome! Looks great! Any plans to make this into a pistol or shotgun configuration?

Based on the layout I think the best configuration would be roughly as so:

[Gaderelguitarist]

Based on the layout I think the best configuration would be roughly as so:

With a frilly apron for the shooter.

[jackssmirkingrevenge]

Do you plan to use the same high mixes that were in previous versions? The silencer sounds fairly effective judging by what little reverb your room has, though it may get pretty loud at 15x.

I could go to higher mixes but I've run out of suitable targets that would actually be worth shooting at for the moment. When I had made this 3/4" pneumatic that could manage just over 50 ft/lbs, I figured I had reached the upper limit of what could be safely tested in an urban area, this one is really pushing it.

I'd be interested to see what effect vents near the back end would have on your silencer(worst case you could always epoxy them shut again).

I've said it elsewhere on this forum and I'll say it again, there isn't a single effective suppressor out there with any holes in the exterior other than bullet entry and exit points. The point of a suppressor is to retain the propellant gasses until the can expand and lose temperature and pressure, what's the purpose of venting them before this is achieved?

Based on the layout I think the best configuration would be roughly as so

Good one

Anything this size would be silly in a "finished" configuration, but there is some renewed inspiration to make a suppressed pistol or shotgun, with greater focus on sound suppression than MOAR POWAH!

Here's a 1000 frames per second closeup of the ignition shining through the epoxy plug at 6x, you can clearly see the ignitior spark followed by the mixture burn. This was without a projectile and it was extremely loud, naturally there's nothing to direct the gasses into the suppressor instead of straight out the muzzle. Note how quickly the flash dissipates once the disk bursts:

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[ramses]

That's amazing! makes me almost reconsider selling my EX-F1

[Gun Freak]

That ignition video was really cool!
Great work on the hybrid. This is a beast.

[jackssmirkingrevenge]

Thanks. I have a bit of clear tube from a dessicant cartridge, I was thinking of making an all-clear combustion for high speed filming purposes...

[Ragnarok]

I've said it elsewhere on this forum and I'll say it again, there isn't a single effective suppressor out there with any holes in the exterior other than bullet entry and exit points.

That's not entirely true. My experience with barrel porting (venting straight to atmosphere) is that, if done in certain ways, it can reduce peak decibel levels by way of a slower, longer release of air than just "uncorking" a pressurized barrel all at once.
Of course, this means it's not very efficient as porting (as it's not dumping the air fast enough to really reduce the muzzle blast), and it's nowhere near as good as a dedicated suppressor.

But, theoretically, if controlled, a modest release of air from the suppressor via some form of venting ports could help provide a longer, slower release.
However, actually controlling it would be a nightmare - and given the relatively small vents you'd need and the very short time scale available to get the gasses through them, any effects would be minimal.

The reason that it's not done is because that even if done right, there's almost nothing to be gained, and it's very easy to get it wrong.

[jackssmirkingrevenge]

The reason that it's not done is because that even if done right, there's almost nothing to be gained, and it's very easy to get it wrong.

The thing is that this effect is catered for in most suppressors not by cutting holes in the tube but by increasing the size of the baffles towards the exit, which effectively "leaks" some of the gasses ahead of the projectile to prevent the "uncorking" noise aspect.

I haven't done it with this suppressor mainly because it would cause issues with some projectiles, indeed if you look at shotgun suppressors the also use a full length tube to avoid interference from the wad.

[jakethebeast]

there is only one word that i can say

BUENO

[jackssmirkingrevenge]

This project had been set aside due to some leaking issues in the burst disk area that I finally seem to have resolved. To celebrate this fact, some video.

Followinghybrid shotgun fail, I give you hybrid shotgun win!

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At 9x, this time using an actual 12 gauge wad and 9 x0.177" lead BBs

[jackssmirkingrevenge]

It's Sunday and the light is good, so I wheeled this out for some more shots

UPS case looking snazzy in novelty eyewear, a CO₂ capsule at 9x soon put a stop to that:

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Old modem, projectile loading fail that was not at all good for my hearing still, pretty cool shot, you can see the glowing fragments of photo paper burst disk hitting the modem:

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Same target, projectile loaded this time at 9x went straight through the modem and the steel sheet behind it:

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[Labtecpower]

I really have to try this

Do you have some more information about your syringe fueling?


And btw, have you considered using glow-plugs instead of spark gaps?
I dont know if they get hot enough, but I think they are usable to a lot higher mixes.
and, last but not least, I hate piëzo igniters.

[jackssmirkingrevenge]

I really have to try this

I used to be suspicious of hybrids, but now that I've made a few I don't think I would really make another single shot pneumatic unless compactness was required (as in the case of a pen gun).

Do you have some more information about your syringe fueling?

Nothing to it, here's the setup:



I'm using a mixture of propane and butane, so I calculated a 3.5% fuel concentration per mix number. Basically add your chamber volume to the dead volume of the pump (in the case of my Beto shock pump it's 1.75mL), multiply by 0.035 then by the mix number. Fill the syringe to the calculated volume, inject in chamber, close burst disk and pressurise.

Anyhow, finally decided to take it to 12x - EPIC FAIL

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The barrel shot out of the suppressor, 30 gram projectile missed the target and slammed directly into the backstop, still haven't found it still, it managed to register a chrony reading, at 544 feet per second that's a muzzle energy of 304 ft/lbs, by far the most powerful shot I've ever fired from one of my launchers.