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Mk IV QEV Popoff. Updated 22 Feb

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: SubsonicSpud » Sun Apr 19, 2009 6:59 am

psycix wrote:Nice! It seems like the stops really helped feeding.


Yes definitely improved.

I made a better stop today, out of a eraser refill, no longer jammed like in the closeup Tee video I posted earlier

Image


john bunsenburner

They are just split shot sinkers about 2.5 - 3 gram each. I buy them in a bulk pack of 150 at Kmart for about AUD$4.50

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Unread postAuthor: jackssmirkingrevenge » Sun Apr 19, 2009 7:24 am

Fantastic results considering you're using such irregular ammunition - seriously, but some 8mm ball bearings!
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Unread postAuthor: SubsonicSpud » Sun Apr 19, 2009 7:51 am

jackssmirkingrevenge wrote:Fantastic results considering you're using such irregular ammunition - seriously, but some 8mm ball bearings!


Spilt shot sinkers are pretty average for ammo, but I sort out the worst, and also squeeze the gap in them closed as I load them in the mag.

8mm steel BBs would have been good in the old barrel, but the new one is about 7mm, along with the tee mag. I still have no idea what calibre to make the final version of this gun. The sinkers I have been using seem to be the only reasonably economical thing to shoot and still have a high density, so I an inclined to stick with what i have got :( Just another hurdle to jump over with full auto :?

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Unread postAuthor: jackssmirkingrevenge » Sun Apr 19, 2009 8:05 am

You're never going to get reliable and efficient feeding with such horrible ammo though, not to mention all the air you're wasting in the barrel. Have a look on ebay, you can get steel bearings of various sizes at a reasonable price, and unlike lead sinkers they're 100% reusable - if you're careful with where you shoot, you can recover most of them with a bit of patience and a strong magnet.
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Unread postAuthor: FragmentedSanity » Mon Apr 20, 2009 4:32 am

Hey SubsonicSpud, and other fellow Aussies in search of the ultimate Ammo for your smallbore cannons. Certain reloading supplies can be purchased without a firearms licence from a gunshop without question or strange looks or anything :P
Im refering of course to shot used for reloading shotguns. It comes in all sorts of sizes, im sure youll find one thats just right.

Below is a link to a chart that shows the size of various shots - Its American, but im fairly sure that the shot sizes are the same.
http://www.thefiringline.com/forums/attachment.php?attachmentid=26451&d=1188069348

The best part is that it comes in big bags. Has to be cheaper and better quality than sinkers.

Hope this helps some - just check out your local gunshop and be amazed at the availability of bags of perfectly sized round balls of lead, or steel - then post lots of vids of mass destruction for all to enjoy :twisted:
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Unread postAuthor: jackssmirkingrevenge » Mon Apr 20, 2009 6:17 am

You can say that you're using the shot as a counterweight (model yachts, for example) or for casting as it's easier to melt.
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Unread postAuthor: SubsonicSpud » Mon Apr 20, 2009 7:08 am

FragmentedSanity wrote:Hey SubsonicSpud, and other fellow Aussies in search of the ultimate Ammo for your smallbore cannons. Certain reloading supplies can be purchased without a firearms licence from a gunshop without question or strange looks or anything :P
Im refering of course to shot used for reloading shotguns. It comes in all sorts of sizes, im sure youll find one thats just right.

Below is a link to a chart that shows the size of various shots - Its American, but im fairly sure that the shot sizes are the same.
http://www.thefiringline.com/forums/attachment.php?attachmentid=26451&d=1188069348

The best part is that it comes in big bags. Has to be cheaper and better quality than sinkers.

Hope this helps some - just check out your local gunshop and be amazed at the availability of bags of perfectly sized round balls of lead, or steel - then post lots of vids of mass destruction for all to enjoy :twisted:


I was going to look into that myself, was just a bit paranoid at walking into a gun shop and asking for the stuff. In the meantime I have ordered off evil bay a pack of 1080 1/4" steel ball bearings from the US :twisted: It is actually cheaper doing that then buying them in Australia. Works out to be about 1cent more per round than the split shot sinkers. The new design I am making will be based around a 1/4 projectile, so will be perfect for 1/4 Steel BBs and No.3 lead buckshot. :D

FragmentedSanity, Thanks for that link, I had seen similar but without as much detail.

JSR, That was actually an excuse I was thinking of :D

By the way, dose anybody have an idea of where to source a very long soft spring, something about 60-80cm long and less than 1/4 diameter? Need it as a mag spring. I'm thinking I am going to have to wind up some piano wire into the required length.

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Last edited by SubsonicSpud on Mon Apr 20, 2009 7:41 am, edited 1 time in total.
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Unread postAuthor: CpTn_lAw » Mon Apr 20, 2009 7:23 am

WOOOOOT I love the sound it makes from the 1/2" plywood perspective!! sounds like a supressed machine gun shooting!!! i love that!!
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Unread postAuthor: SubsonicSpud » Mon Apr 20, 2009 7:39 am

CpTn_lAw wrote:WOOOOOT I love the sound it makes from the 1/2" plywood perspective!! sounds like a supressed machine gun shooting!!! i love that!!


It dose sound great, unfortunately the true sound of it dose not come through to well on the videos because of the noise cancellation on the camera. Hence why the first shot is usually loud, with the rest more muffled. The cracking noise it makes isn't really audible on the video, but it echos around the hills here.

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Unread postAuthor: SPG » Mon Apr 20, 2009 7:47 am

Where are you putting your spring mate? Obviously it's a mag fed set up, but is it likely to be straight or coiled?

I had a thought for anyone using steel BBs, which'd be to use a good strong magnet on the opposite side of the magazine's mouth. The idea would be that the magnetic forces would do whatever they do in steel, and so al the BB's would be attracted allong the magazine to the breach. Might work, you never know.

Another option would be to use something like one of these

Image

retractable lift pass holders which work like a tape measure to pull your ammo out of the magazine, rather than have a spring pushing it from behind. As long as your magazine tube's got enough room to allow the very thin nylon line down between the walls and the BB's then you could attach the end to a magazine follower, and the rest should be pretty obvious.
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Unread postAuthor: SubsonicSpud » Mon Apr 20, 2009 7:58 am

the spring was going to be behind the ammo, pushing it into the tee. I want to be able to use lead shot in it as well, so a magnetic system will not work. I like the idea of a tag reel, but I don't think it would be durable enough, or have enough tension.
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Unread postAuthor: SPG » Mon Apr 20, 2009 8:05 am

Well if not a tag reel then go up one point and use one of those retracting keychains. The spring on that's a little bit stronger and the whole thing is a bit sturdier.

Still too weak? You could always go for a dog lead.

Image

Second thought, would be an air-spring with an airtight magazine follower, something like a piston out of a small syringe would be excellent Put a short spring in front of this to "take up the slack" . You could either pressurise your magazine with something like a schraeder and a pump or if you want to get your own back on JSR harping on about wasted air with pop-off's then pipe that to the far end of the magazine.

I've worked that system out in greater detail but it'd depend a bit on the layout of magazine in relation to breach/barrel etc.
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Unread postAuthor: SubsonicSpud » Tue Apr 21, 2009 6:23 am

Just another update, Here is a bit of a concept of the final version construction:

Image

Basically the Magazine Tee and QEV will be produced out of a single block of Polycarbonate to reduce size, increase durability and also reduce the dead space between the valve and projectiles. The air chamber could also be incorporated into the same block with a bit of extra work.
I am thinking as developing this as a small radio controlled gun turret, as opposed to a handheld weapon, just for something different :twisted:

SPG, I still think having a system where a string is pulling the ammo down the mag would be problematic, particularly allowing air to bypass the ammo in the mag and cause power loss. It could possibly cause jamming as well.
I am tossing up whether to use a pneumatic mag spring or just a normal spring. I guess I could even try hopper feeding through a flexible tube and use the pop off waste air to drive the ammo up the tube, It would definitely be good to make use of that wasted air.

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Unread postAuthor: jackssmirkingrevenge » Tue Apr 21, 2009 6:37 am

That is precisely what I had in mind, with the mag in line with the barrel, especially as my final project will likely be based on the FN P90 in terms of configuration:

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Unread postAuthor: POLAND_SPUD » Tue Apr 21, 2009 7:16 am

jesus I need to buy a drill press... you used a drill press to make the T right ?? it seems so clean and easy to build - I've been struggling for weeks to add some sort of a detent to minimize double feeds
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