Most of you are probably aware of my pneumatic pen-gun, this is an extended version of the same concept. Chamber size is roughly double and barrel length is almost three times that of the original, so it clearly no longer fits in the "pen" category.
I've also used a different piston configuration, with the piston now being solid rubber cut from 1/4" thick sheet as shown below:
Otherwise, construction and materials are the same as the first version, have a look at the how-to here for details.
The idea is to evaluate the power potential of this small (2.5mm, roughly one tenth of an inch) calibre with a reasonably sized barrel and chamber taken to high pressures (300 psi+) and if successful, fabricate a coaxial suppressor and later a pistol grip to enable the unit to be operated in a conventional manner.
So far I've only been able to test it to 150 psi but I should have one of these beto shock pumps on the way, gauge goes up to 400 psi so expect significant performance results soon.
How it works:
edit 30/01/2010:
high speed target footage:
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edit 01/03/2009. damage video:
[youtube][/youtube]
steel bolt section fired at 400 psi at a gamo tin.
Until then, some pics:
Posted: Sun Dec 28, 2008 7:15 am
by Carlman
Nice work mate!
But i agree with your fears in the other thread, i think the rubber piston will expand to much when high pressure is applied
Posted: Sun Dec 28, 2008 9:17 am
by jackssmirkingrevenge
Carlman wrote:I think the rubber piston will expand to much when high pressure is applied
It's been fine so far, it's cut fairly roughly so I'm hoping it will be ok. Time will tell, can't wait for that shock pump to arrive.
Brilliant time to visit ebay.co.uk at the moment thanks to the exchange rate also bought a CO<sub>2</sub> tyre inflator, expect a machine pistol soon
Posted: Sun Dec 28, 2008 9:22 am
by ALIHISGREAT
jackssmirkingrevenge wrote:
Carlman wrote:I think the rubber piston will expand to much when high pressure is applied
It's been fine so far, it's cut fairly roughly so I'm hoping it will be ok. Time will tell, can't wait for that shock pump to arrive.
Brilliant time to visit ebay.co.uk at the moment thanks to the exchange rate also bought a CO<sub>2</sub> tyre inflator, expect a machine pistol soon
thank Gordon i remember when the £ was 1:2 against the $... happy times... now its just crap against everything.
Posted: Sun Dec 28, 2008 9:38 am
by Sticky_Tape
Video? Nice gun how long is it in inches?
Posted: Sun Dec 28, 2008 9:55 am
by jackssmirkingrevenge
Sticky_Tape wrote:Video? Nice gun how long is it in inches?
Videos will come when I get the shock pump as it's pointless testing damage now. Total length is 38cm, that's just under 15 inches.
Posted: Sun Dec 28, 2008 11:35 am
by Sticky_Tape
It's not pointless it can still do somthing.
Posted: Sun Dec 28, 2008 11:41 am
by ALIHISGREAT
yeah but it will be crap at 150psi.
Posted: Sun Dec 28, 2008 11:52 am
by Sticky_Tape
Ok well I'm sure it will be fun with high pressure.
Posted: Sat Jan 03, 2009 5:36 am
by jackssmirkingrevenge
Got my new pump (modded for comfort as seen is the attached picture) and at 400 psi it's a blast!
[youtube][/youtube]
That's a small section of bolt as ammunition at 400 psi straight through a gamo tin (and the polystyrene backing). It's pretty loud too so a detachable suppressor is on the cards.
Did I mention how much I like this pump
Posted: Sat Jan 03, 2009 6:24 am
by ALIHISGREAT
nice to see the piston doesn't compress and expand and that shock pump is pretty tasty... maybe i should mod mine too, its got this terrible tiny handle that would be too small for a 5 year old
Posted: Sat Jan 03, 2009 2:39 pm
by SpudUke5
Looks nice and promising. Now ill prob get the some 1/4 inch rubber so i can finish my pen gun.
By the way, didnt that leave a hole in your wall?
Posted: Sat Jan 03, 2009 3:39 pm
by jackssmirkingrevenge
LikimysCrotchus5 wrote:Now ill prob get the some 1/4 inch rubber so i can finish my pen gun.
I have to say this piston really is the mutt's nuts, childishly simple to make , so problem with attaching a separate seal, durable and works great at high pressure, unlike the original pengun that leaked above 200 psi and never had its true potential realised.
By the way, didnt that leave a hole in your wall?
What's another hole
Posted: Sat Jan 03, 2009 3:52 pm
by Gippeto
Very nice Jack. It's "sleek" looking.
Does your new shock pump open the schrader valve too? Looks as though it might.
Cracking pressure be damned.
What's another hole
Ahh to be single.
Posted: Sat Jan 03, 2009 3:58 pm
by jackssmirkingrevenge
Gippeto wrote:Does your new shock pump open the schrader valve too? Looks as though it might.
Yep, that purple anodised bit is a separate threaded bit that presses the stem independently.
Cracking pressure be damned.
Actually I modded the shcrader somewhat, if you can call it that. Basically clipped off the the bulged bit that stops the stem from coming out and stretched it a bit, seems to have weakened the spring to the point that there's practically no resistance.
so expect significant performance results soon.
also bought a CO<sub>2</sub> tyre inflator, expect a machine pistol soon 
i remember when the £ was 1:2 against the $... happy times... now its just crap against everything.
