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How to make a bolt action?

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 to make a bolt action?

Unread postAuthor: hydrolyzer » Mon Mar 24, 2014 10:36 pm

Hi guys, I've been searching the forum for a month trying to sort out how to assemble what I'm going for. Hopefully one of the more experienced builders here will be able to help me put the pieces together.

I'm going for a high power bolt action or semi auto 6mm design. Hoping to build it 'valveless' like polandspud and jsr have done. I have a (piston?) valve I got from a pressure washer handle. Rated to 3500psi and it has a 6mm Id steel tube fixed to its exhaust.

I hope to use an oring in a compression fitting to control the 'release' pressure. (I'm having trouble finding a compression fitting small enough to fit my 8mm od tube but that's something I can handle myself.) I was originally going for semi auto with a spring loaded tube feeding into the barrel, but it seems impossible to place the tube inlet close enough to the oring to stop double feeds due to the bulk of the compression fitting.

My alternative then is to go for a bolt action. My understanding is to drill a hole in the barrel big enough for the projectile. (What shape is best if I want to have the option to use diabolo pellets?) behind this hole have a tube inside the barrel that has a rod or what have you protruding through the barrel. Ammo goes in, tube slides forward pushing the ammo up to the oring. How do I prevent the air going around the edge of the tube? Obviously fit as tight as possible, but I feel at 400 psi I'm still going to get leakage. Do I just accept these losses?

I could use a spring loaded ball detent to get the spring loaded tube magazine back, in this instance does the magazine become part of your chamber (more air wastage?) or in practice does the ammo usually seal off the magazine?

Finally my valve has an M22 male connection and my paintball tank is ASA. For the connection I plan on using 1/8" NPT grease gun line (4500 psi). My plan for this is to buy two brass rods, drill clean through (small diameter hole) then drill both sides to the appropriate sizes so I can use a hand tap to thread them as female M22/1/8" and 1/8"/ASA. My question is if this will work on the ASA end. I think the regulator has a pin that needs to be depressed or something. Would it be better to get a paintball remote line and make an adapter for that to M22? Could someone confirm for me before I make a purchase that the remote line doesn't need a pin depressed also and that it is also ASA?

In simple terms, if I connect a remote line to my paintball regulator and open the tank, will air start spraying from the end of the remote line?

Wall o' text but these are all the questions I couldn't answer by searching. Also in searching I've noticed a strong tradition of people saying "disregard everything you have done so far and buy an eBay qev+slide valve." I've already determined I don't want to do this.

Cheers!
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Re: How to make a bolt action?

Unread postAuthor: jackssmirkingrevenge » Tue Mar 25, 2014 5:11 am

hydrolyzer wrote:Also in searching I've noticed a strong tradition of people saying "disregard everything you have done so far and buy an eBay qev+slide valve." I've already determined I don't want to do this.


This advice is usually given to people who either lack the skills, tools or resources to make a high performance valve setup.

With regards to questions pertinent to your project, have you seen this build? airsoft-pellet-guns/topic21684.html
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Re: How to make a bolt action?

Unread postAuthor: dajoro » Tue Mar 25, 2014 10:01 pm

I've been studing this photo of a bolt-action PCP airgun for a while. Take a look , many parts and quite complicated but beautiful.
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Re: How to make a bolt action?

Unread postAuthor: hydrolyzer » Wed Mar 26, 2014 3:54 am

Thanks for that link, replacing the compression fitting with a T will certainly solve the mag inlet placement issues.

I guess no known answer on the other questions, but i can disregard the bolt action queries for now as they are no longer pertinent.

That mechanism sure looks beautiful, but in my 30 second inspection I couldn't ascertain how it functioned. Is that from a thread or webpage with more information?
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Re: How to make a bolt action?

Unread postAuthor: jackssmirkingrevenge » Wed Mar 26, 2014 5:56 am

hydrolyzer wrote:That mechanism sure looks beautiful, but in my 30 second inspection I couldn't ascertain how it functioned. Is that from a thread or webpage with more information?


This was my interpretation:

The bolt is pulled back, exposing the magazine port and simultaneously cocking the hammer that is caught by the trigger. The pin on the magazine is pushed, introducing a single projectile into the breech, then the bolt is pushed forward again and locked in place.

For firing, the trigger is pulled, releasing the hammer which strikes the valve stem, momentarily opening the valve which allows a burst of air to move through the transfer port and propel the projectile out of the barrel. The cycle can then be repeated.


Image

I think the regulator has a pin that needs to be depressed or something. Would it be better to get a paintball remote line and make an adapter for that to M22? Could someone confirm for me before I make a purchase that the remote line doesn't need a pin depressed also and that it is also ASA?


Image

The end on the right goes on the tank, and the knob on top is the on/off control. You turn the knob clockwise to depress the paintball tank pin and allow air into the system. This means that you can have the bottle permanently connected but not necessarily with air in the system. Apologies if that wasn't your question :oops:
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Re: How to make a bolt action?

Unread postAuthor: hydrolyzer » Wed Mar 26, 2014 7:52 pm

That was exactly my question!

Now I know that I can get one of those lines and adapt it directly to my pressure washer valve.

That bolt action diagram makes sense, and I think if I develop the desire for something more challenging than my current project that will definitely be on the shortlist.

All help is much appreciated.
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Re: How to make a bolt action?

Unread postAuthor: jackssmirkingrevenge » Thu Mar 27, 2014 4:57 am

hydrolyzer wrote:That was exactly my question!


*phew*

didn't want to sound like I was treating you like a simpleton :)
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Re: How to make a bolt action?

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