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1300 Foot Pounds large bore airgun

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I must apologize. There is an error in the results of the test. I've recovered one of the spent bullets and realized I was using lighter bullets for the test. I've machine those bullets in small batches of various sizes and the 23 grams was mixed with the 18.5 grams bullets. So the weight used in the video was 18.5 gram (293 grain). Consequently the energy is 1055 ft/lbf (1430 Joules).

Please forgive me. I was away from the shop for some time and eager to start the testing. And in some way fooled myself by the excitement. I will make anew video - including all the technical details - to replace the current one.
 
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Uploaded a new video:



https://www.youtube.com/watch?v=hnmhKNyoKlQ



This one includes a link to full details.

I am sorry if I was a bit secretive and did not show all the information initially. Maybe now, that it is all disclosed, it does not look that interesting anymore. I doubt very much if this has any commercial value, but I did apply for a US patent (provisional) . I am afraid this will be the worst investment of $70.00

At this stage of development I am looking at reducing the consumption of the air and some easy way of ejecting the spent disk.
 
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That is pretty cool! How will you make the electronic triggering and air delivery consistent to shrink the ES of the FPS?
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I don’t think 70fps for an ES will change anything down range at 1000FPE haha! That is still hole in hole at 200yds as far as BC is concerned. And if this is a hunting tool, as the energy suggests, anything it makes contact with is super dead even at half the FPE.
 
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Sorry for not replaying sooner. Heath issues again and no work or even computer for the last week. Seems that curing one issue can upset other....
I must admit the results did surprise me. Since then I have had only two chances to to run tests with the rupture propagated simply by gradual pressure increase with the electrode removed. The burst pressure was bout 3500 psi for the bras cartridge and another one one with the lead cartridge and cemented (stainless this time) disk about 4000. The chronograph missed the reading on that one but the brass cartridge, some 13 gram (200 grain) without the flange, clocked only 850 f/sec (259 m/sec).
So, friends, I am just as puzzled as you are. It is quite possible that the actual spark has something to do with it especially since there is was fair amount of grease on the orings and consequently on the foil. By itself it might not be a bad situation if it works to increase the energy.
I have noticed as well another issue. With the test shown in the video there were little fragments of the peat moss dispersed all around. With the brass bullet I did not have the peat moss bag (I placed it as to stop any ricocheting slugs, But since those in the previous tests either went clean through the 2x10 or got deeply embedded. I did not have it in the last test. I am wondering if some of this flaying debris could have been affecting the chronograph. Still, the slug seemed very powerful in one occasion penetrating the moss and the board and the other getting deeply embedded partly sticking out through the other side of the board (that is how I've discovered my error in the projectile mass). Forgive my arrogance and showing only the through hole...
There is a lot to test. All the tests must be repeated many times and evaluated. As well I want to change the setup and to space the "gun", the chronograph and the target - it was easy just to place it all near the door of my gas storage room where my high pressure air pump is plumbed permanently as well. There is as well the issue of easily ejecting, preferably automatically, the spent disk. For the record I should add that the actual calibre is 11.12mm or 0.438". This is a result of past attempts (years ago) at making my own barrels using shop made rifling button that ended to be undersized and consequently reaming the bore to this size before rifling. Altogether the barrel is poor and my intention is to get a Lothar Walther for next tests.
As it is, for now I will have to abandon the development and deal with the health issues and some family problems that have emerged recently. Thank you for the comments and interest.
 
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That's a very interesting build you're doing. I hope your health,etc.will improve so you can continue it.I was thinking, and my apologies if someone has already thought of this, but I bought a cordless 16ga. nailer. It will drive a 2 1/2 inch finish nail in oak. Could that power be used to fire a projectile in a gun? Ron
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No not really.

The gas explosion is weak and works on a large piston with a pin that hammers the nail in.

There is simply not enough force/energy in the gas explosion to accelerate a projectile in a meaningfull manner.


 
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Chickenthief, Sorry, I forgot about the butane gas type. Mine is the Milwaukee m18. It , from my understanding, uses a motor to wind a very heavy spring which releases to fire.
Click to expand...

That's a very interesting build you're doing. I hope your health,etc.will improve so you can continue it.I was thinking, and my apologies if someone has already thought of this, but I bought a cordless 16ga. nailer. It will drive a 2 1/2 inch finish nail in oak. Could that power be used to fire a projectile in a gun? Ron
Click to expand...


No not really.

The gas explosion is weak and works on a large piston with a pin that hammers the nail in.

There is simply not enough force/energy in the gas explosion to accelerate a projectile in a meaningfull manner.

Click to expand...

The actual energy of a nail gun like the Paslode cordless XP Framing Nailer is considerable but, as observed, it is a relatively slow expanding, low pressure gas (from the combustion) in a large cylinder. It might be possible for the piston instead of driving a nail to drive a secondary, small diameter piston to compress air to much higher pressure. The pressure ratio will be the same as the ratio of the piston area. But the whole concept is too complicated and cumbersome. 
 
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