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Co-axle, bolt-action, barrel-mag?

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Co-axle, bolt-action, barrel-mag?

Unread postAuthor: NetherPhoenix » Tue Apr 21, 2009 7:40 pm

Ok, right now I am in the design stage for a paintball/similar-sized-object sniper rifle. In my head i wanted to make it a co-axle. barrel mag, bolt-action. Unfortunately, i can't seem to visualize how these would all fit together. Am I trying to combine incompatible features? Any advice would be much appreciated.
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It's times like these that i wonder, what would Carlos Hathcock do?
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Re: Co-axle, bolt-action, barrel-mag?

Unread postAuthor: Moonbogg » Tue Apr 21, 2009 8:10 pm

NetherPhoenix wrote:Ok, right now I am in the design stage for a paintball/similar-sized-object sniper rifle. In my head i wanted to make it a co-axle. barrel mag, bolt-action. Unfortunately, i can't seem to visualize how these would all fit together. Am I trying to combine incompatible features? Any advice would be much appreciated.


What is barrel mag? Does that mean a magazine that feeds into the barrel?
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Unread postAuthor: ramses » Tue Apr 21, 2009 8:36 pm

coax and bolt action don't go well together, there is craploads of deadspace. Deadspace is basically unused volume where propellant gas can expand and not do any useful work. Over/under would have to be the configuration unless you want a significant decrease in performance and/or air efficiency.

This "barrel mag" idea could do with some explaining. Perhaps a diagram?
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Unread postAuthor: inonickname » Tue Apr 21, 2009 8:55 pm

Co-ax and bolt action weren't born to be together. With a lathe and a lot of work you could do it but breech loading would be more effective.

If you want an inline piston valve and bolt action you could try a toolies valve.
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Unread postAuthor: grock » Tue Apr 21, 2009 10:32 pm

i think barrel mag means something under the barrel, like a shotgun. and if so, that wont work very well with coax or bolt action (could work with BA though)
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Unread postAuthor: mark.f » Tue Apr 21, 2009 11:01 pm

inonickname wrote:Co-ax and bolt action weren't born to be together. With a lathe and a lot of work you could do it but breech loading would be more effective.

If you want an inline piston valve and bolt action you could try a toolies valve.


Or a "quick-dump valve" as seems to be popular.
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Unread postAuthor: jook13 » Tue Apr 21, 2009 11:14 pm

Or a "quick-dump valve" as seems to be popular.


Haha, it popular because he brings it up so much. Admitadly, the theory behind it is very sound.

If you want a breech load coaxal, it can be very simple. Keep the chamber fairly short. Have the barrel sleeved inside of the pipe that goes through the chamber. The barrel slides out, the ammo goes in, then the barrel slides back in.

Of course the toolies valve previously mentioned works as well.
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Unread postAuthor: Technician1002 » Tue Apr 21, 2009 11:25 pm

mark.f wrote:
inonickname wrote:Co-ax and bolt action weren't born to be together. With a lathe and a lot of work you could do it but breech loading would be more effective.

If you want an inline piston valve and bolt action you could try a toolies valve.


Or a "quick-dump valve" as seems to be popular.


Funny you mention that. I am planning on rebuilding the piston in my ABS test cannon to use a rod instead of a rope for a trigger and use HDPE instead of the slightly leaky PVC. Part of the change I am toying with is a breech spudcutter/loader. The piston would pull all the way out into a 3 inch breech hopper chamber and the bolt would load the spud, cutting it on the way in and lock in place for a quick reload. I don't have a drawing yet, and yes I know :!: :!: Don't use DWV pipe :!: :!: Maybe some year it will fail the pressure test as planned and the ABS DWV test will no longer be a failure. :D
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Unread postAuthor: Moonbogg » Wed Apr 22, 2009 12:05 am

Technician1002 wrote:and yes I know :!: :!: Don't use DWV pipe :!: :!: Maybe some year it will fail the pressure test as planned and the ABS DWV test will no longer be a failure. :D


Lol yeah, no kidding. Now I don't have tons of spudding experience under my belt, but I have yet to see a single shred of evidence pointing to cellular core ABS failing any more often than, oh say, PVC, aluminum, steel, titanium, unobtainium etc.

I like your idea a lot actually. It presents a challenge and requires some thought. Bravo for that alone! You got me thinking now. How improper of you.
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Unread postAuthor: Technician1002 » Wed Apr 22, 2009 12:17 am

Moonbogg wrote:
Technician1002 wrote:and yes I know :!: :!: Don't use DWV pipe :!: :!: Maybe some year it will fail the pressure test as planned and the ABS DWV test will no longer be a failure. :D


Lol yeah, no kidding. Now I don't have tons of spudding experience under my belt, but I have yet to see a single shred of evidence pointing to cellular core ABS failing any more often than, oh say, PVC, aluminum, steel, titanium, unobtainium etc.

I like your idea a lot actually. It presents a challenge and requires some thought. Bravo for that alone! You got me thinking now. How improper of you.


The only videos I find online of failures so far have been due to the flexibility with cleanout caps blowing off, and the oxyacetylene guys splitting out the seam. I found absolutely no ABS failure photos or videos online for low pressure cannons. PVC shrapnel videos and photos are common. It was worth testing.

A lot of PVC failures and combustion folks using it was the reason for the test.
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Unread postAuthor: i-will » Wed Apr 22, 2009 1:04 am

a bolt action piston rifle is exactly what i plan to do. this is just a quick mock up of the co-ax bolt. the co-ax is the bolt and the piston has been changed a bit. i'm also gonna install a hammer valve so i can use a real trigger system to pilot (give it the real feel of firing a rifle). i'm pretty sure that most of us know how a mag works so i didn't put much effort or detail in illustrating it. i'm open to any suggestions.<a href="http://s90.photobucket.com/albums/k273/PROGRESSKATE/?action=view&current=pistonbolt.jpg" target="_blank"><img src="http://i90.photobucket.com/albums/k273/PROGRESSKATE/pistonbolt.jpg" border="0" alt="PISTON BOLT"></a>
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Unread postAuthor: NetherPhoenix » Wed Apr 22, 2009 7:12 am

ramses wrote:coax and bolt action don't go well together, there is craploads of deadspace. Deadspace is basically unused volume where propellant gas can expand and not do any useful work. Over/under would have to be the configuration unless you want a significant decrease in performance and/or air efficiency.

This "barrel mag" idea could do with some explaining. Perhaps a diagram?


grock wrote:i think barrel mag means something under the barrel, like a shotgun. and if so, that wont work very well with coax or bolt action (could work with BA though)


yeah, thats the basic idea, but i think i might just ditch the idea and try to go with a regular tube or box mag. it will make things a lot simpler.

as for the coaxal, i think i'll just go with the bolt-action as my primary concern, even if not doing a coaxal will increase the overall size of the gun.
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Unread postAuthor: i-will » Wed Apr 29, 2009 4:43 am

if u do some planning u'll probably find that u don't need to make the coax huge. just make if the right volume for the barrel. i think u should stick with the idea. also the piston in my pic is actually easier to make than the usual coax and will seal better. it will also eliminate the deadspace that everyone complains about. keep the idea alive.
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Unread postAuthor: NetherPhoenix » Thu Apr 30, 2009 7:13 am

yeah, i can see how it would be easier, so i'll make the idea work somehow
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