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How do you guys build decent bolt action/breech loaders?!

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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How do you guys build decent bolt action/breech loaders?!

Unread postAuthor: kiwi of nitro » Wed Dec 17, 2008 3:11 am

I can't find 2 sizes of PVC that fit into each other well enough to make an effective bolt action loader...

Like the one on BCARMS...

Image


Do you know what fittings and pipe were used for that?

I'm looking to build one for feeding C cell batteries into a 1" barrel.

I've got Plexiglas to build a neat rectangular hopper for the batteries, I just can't find pipe or fittings that seal nicely around 1" pipe...

I built one out of an expansion repair joint that worked OK, the locking mechanism broke just about every time I fired it though!

I want to try it differently like the one shown above.
Any insight would be greatly appreciated.
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Unread postAuthor: Davidvaini » Wed Dec 17, 2008 4:03 am

Not sure if this helps, but...

3/4" coupling fits in 1.25" pipe
1.25" coupling fits in 2" pipe

those sizes are pretty close to each other..
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Unread postAuthor: ALIHISGREAT » Wed Dec 17, 2008 4:50 am

if you are making a semi, and need the hopper, why not just use a blow foreward bolt? this would make it auto loading.

and if you aren't making a semi, then there are much easier ways of making a bolt action

check out Rag's HEAL, it uses a system where the barrel slides foreward.

Image


http://www.spudfiles.com/forums/heal-320psi-20mm-copper-cannon-now-with-damage-videos-t11453.html
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Unread postAuthor: Ragnarok » Wed Dec 17, 2008 5:07 am

Wow, I don't even need to publicise my own work any more, other people are doing it for me. :D

To add to what Ali said, for the design I used, it's not important to have two close fit pipe sizes. The outer pipe in the breech loader is not a tight fit, and indeed wouldn't work if it were, as the jubilee clip that fits around the barrel has to exist somewhere.

The only tight fits made are between the 22mm OD barrel and the 22mm fittings into which it is mounted. These 22mm fittings are then fixed to the inside of the 28mm outer layer of the pipe (in my case, at the front, by using a copper ring I made to fill the space, and at the back, utilising a solder-ring fitting, for which the size fits straight off into 28mm)

The two sizes of coupling/pipe compatibility Davidvaini mentioned could be put to good use here. Have a 1.25" barrel in a 2" outer sheath, or a 3/4" barrel in a 1.25" outer sheath. Either would work.
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: VH_man » Wed Dec 17, 2008 7:02 am

Davidvani forgot to mention that 1in pipe fits inside of 1.25in pipe quite easily as well.

Not to mention, One of the BEST breech loaders is a Union or male/felamle fittings. Quite simple. Doesnt look sweet, but its actually, in my mind, more functional than other methods of breech loading.
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Unread postAuthor: scavies » Wed Dec 17, 2008 5:31 pm

I put a thin brass or copper pipe inside of the PVC pipe, bent in the back ends, so it catches air, and then put a spring in front of the pipe.

Put a hole on top of brass barrel so the ball can drop in.

So the action goes like so

Air hits barrel, barrel flies foward so hole is exposed to T cartridge, next shot drops in, barrel flies back which covers the hole to leakage and is ready for the next shot.

That's a simple semi-auto blow foward breech.
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Unread postAuthor: raptorforce » Fri Dec 19, 2008 1:48 am

scavies wrote:I put a thin brass or copper pipe inside of the PVC pipe, bent in the back ends, so it catches air, and then put a spring in front of the pipe.

Put a hole on top of brass barrel so the ball can drop in.

So the action goes like so

Air hits barrel, barrel flies foward so hole is exposed to T cartridge, next shot drops in, barrel flies back which covers the hole to leakage and is ready for the next shot.

That's a simple semi-auto blow foward breech.


but a copper barrel is quite heavy i had a simliar idea under theories. but it the barrel and air chamber do not move only a piece a little bigger then the projectile would have to move. have yet to draw it and post
been playing to much combat arms and building airplanes
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Unread postAuthor: raptorforce » Sat Dec 20, 2008 4:38 am

i need some help with my bolt action it uses a 3/4 inch connector which is pushed against a 1 inch pipe and when i fire it somehow the air unlocks the bolt and throws the barrel forward really wierd
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Unread postAuthor: btrettel » Sat Dec 20, 2008 7:16 am

If you're shooting small things (< ~5/8 inches in diameter) and don't mind foot long barrels, telescoping brass tubes are perfect for this. They're sold at most hobby stores and online. McMaster-Carr sells them.

These tubes are good because there are many sizes of them and successive sizes fit inside each other smoothly and are air tight under most barrel pressure conditions.

You can make a longer barrel by connecting multiple tubes, but I'm not sure how the lip would affect performance. I don't imagine it would have a major effect but I also don't know.
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Unread postAuthor: cheeseboy » Sat Dec 20, 2008 8:33 am

expanding on what btrettel said hobby shops store -at least mine does- brass tubing in sizes that progress upwards be 1/32 of an inch between each size, the biggest being 1" these sliding together are air tight and in my barrel I have soldered 2 together and the lip does not make a difference to performance (as opposed to a brake line of a just bigger size)

in response to your problem your bolt action probably just has a notch that the bolt fits into: (sorry for the bad diagram its just struck midnight here!)
___ - __
- l__l
but for a more reliable lock it should look like this:
___- - ___
- - l - l___
- - l______l

if yours looks like the second one, then I don't know whats happening :oops:
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Unread postAuthor: pocket » Sat Dec 20, 2008 9:29 am

lol cheese boy im pretty sure nobody has a clue what your pointing out in your diagram. How about you spend 5 seconds in MS paint and make another attempt to get your point across.
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Unread postAuthor: cheeseboy » Sat Dec 20, 2008 6:26 pm

I actually made one pocket, but then I couldn't get it to work I got the red square of death and it was 12:00 in the morning, hopefully someone else gets what I an saying and will do a better job. for a how-to on bolt action breech loaders go here :
http://www.spudfiles.com/forums/viewtopic.php?t=310&
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