Home made PCP airgun

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usabro

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Dec 9, 2015
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Maryland
Hey everyone. I'm new here so I'd like to introduce myself. I from Maryland USA, and am 16. I have a few questions so I'll ask them, and I'll be filling out my profile shortly and reading a lot here too.

I've built my own PCP airgun. Single shot, and this is my 4th build. I just have some questions about power of it. First off, the barrel is interchangeable from a .40 caliber steel smooth bore, and a .50 caliber 1/2 inch plastic smooth bore. I usually shoot either shot, which could be anything like button cell batteries, bb's, gravel, pebbles, lead sinkers etc. Or I shoot a large .495 caliber lead sinker with paper towel crammed down the pipe behind it to capture all the pressure. I fill the PVC plastic resovour between 150 and 230 psi. I know PVC can be dangerous but I'm careful not to use outside in the cold, and the pipe and fitting are rated for 480 psi working pressure using water, I guess because water doesn't store much kinetic energy. :)

But my question is does the gun have as much power as a .22 long rifle. I've shot a .22 long rifle before and I know how much kick it has.....barely any at all. And I know that their is a forumla for foot pounds. But I don't have a chronograph and I'm not sure of the weight of the projectile, but if feels about the weight of 4 quarters. And it can shoot through one side of cinder block, or 3/4 inch plywood. Or both sides of 8 soup cans. And it actually has kick, like it doesn't hurt but I can feel the kick in my shoulder. And it goes off with a bang as loud as a .22. It's only accurate within about 6 inches at 10 yards which is pretty bad, but it's designed for power, or super close range hunting, although it's very poorly designed for that use. It seems to shoot slightly faster than a very high powered airsoft gun, when shooting lead sinkers, and about twice as fast when shooting 56 grains marbles.

The pictures are with the .40 caliber barrel. Tell me what you think, and if it has the same or more power as a .22 LR.
Let me know your thoughts and upgrades!

I just realized I can't add pictures.

MOD EDIT: discussion about shooting a human being is not allowed and that part was removed. Also you can find instructions on how to post pictures under the section forum information.

Oh I apologize about that I just was wondering if it would be useful for self defense. And thanks for that information!
 
If you want to know the energy your gun is putting out, you could sight in your gun at a known range, shoot another group at a further distance, and measure the drop of your projectile. All you need is the weight of the projectile, the known distances, the projectile drop, and the BC. Enter all info into chairgun pro, and it will tell you everything. Since you are making your own projectiles, you will have to guess what the BC is by looking up different bullet designs. Not sure what the BC of a button battery is though.
 
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Actually not. I'm not making my own projectiles. I'm buying lead sinkers from Wal-Mart. And about the eye safety, I screwed sheet metal with long screws to contain the pipe if it were to rupture, And I wear a paintball mask a lot with provides adequate protection. Thanks for the concerns and advice though.

@Tactical. I know April 1st is fools day but why should I have waited, I don't get the joke if there is one.

Oh, and my family had problems with crows last year. So I was assigned the task of helping fix that problem. A .495 caliber lead sinker is devastating to a crow, it literally explodes the bird, and the lead sinker will flatten like a pancake if shot against 1/2 inch steel sheets.

I might get a chronograph for Christmas.

Oh and by the way, I don't need to know it about the button battery, that's not being fired by itself, rather just one of the many things I cram down the barrel to use as shot. Sometimes screws, pebbles, gravel, water, bb's, mini lead fish weights/sinkers, nails, paper clips, etc. Basically anything that is metal or dense and small that can have enough momentum to cut through a few water filled milk jugs at 10 feet range.
 
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"usabro" I fill the PVC plastic resovour between 150 and 230 psi. I know PVC can be dangerous but I'm careful not to use outside in the cold, and the pipe and fitting are rated for 480 psi working pressure using water, I guess because water doesn't store much kinetic energy. :)


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Very Dangerous. Water does not compress as Air does.

Look what the pipe manufacture's say......

"WARNING!Never test with or transport/store compressed air or gas in PVC pipe or fittings. Doing so can result inexplosive failures and cause severe injury or death."


http://www.charlottepipe.com/Documents/PL_Tech_Man/Charlotte_Plastics_Tech_Manual.pdf
 
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Dad won't let me get a real airgun, because he thinks I'll break windows or get hurt, but he doesn't realize this gun has more than enough power.

And about the pipe, yes it is dangerous, that's why it's contained in thick metal. I'm thinking of replacing with steel pipe rated for 2300 psi. I have had one gun explode while filling.

It may be slow moving but it can put a hole in a 1/2 inch thick board at 600 feet. The board is a piece of scrap 8' x 4' plywood.

Also, the trigger if finicky. If the gun is dropped it might fire. So I have to be vert careful while holding it and not have it loaded indoors.
 
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There's some physics you need to study to understand the dangers involved. Compressed air is very different than compressed liquid. Compressed liquid doesn't actually compress much at all and doesn't really have much stored energy. Compressed gasses (any gas) on the other hand is EXTREMELY dangerous. It doesn't matter if it's contained in metal. The expanding gas itself can cause an embolism (an air bubble in your blood stream that is injected through the skin) A small jet of compressed air can actually penetrate your skin and kill you. OSHA restricts the use of compressed air pressure for cleaning to 30PSI or less for this reason.

This is taken from a piece about a different type of airgun, but the concept still applies:
"Due to the serious injuries than can be caused by compressed air, OSHA requirements pertaining to the safe use of safety air guns for cleaning purposes focus on pressure and chip guarding. The federal OSHA requirement can be found in 29 CFR Part 1910.242(b), which states: Compressed air shall not be used for cleaning purposes except where reduced to less than 30 psi and then only with effective chip guarding and personal protective equipment."

Again, I think what you've built is brilliant, but seriously, stop using it. I think you'd be better served by getting a slingshot than firing this gun that you've made. You can move a bigger projectile, faster, and more accurately.
 
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"ztirffritz"There's some physics you need to study to understand the dangers involved. Compressed air is very different than compressed liquid. Compressed liquid doesn't actually compress much at all and doesn't really have much stored energy. Compressed gasses (any gas) on the other hand is EXTREMELY dangerous. It doesn't matter if it's contained in metal. The expanding gas itself can cause an embolism (an air bubble in your blood stream that is injected through the skin) A small jet of compressed air can actually penetrate your skin and kill you. OSHA restricts the use of compressed air pressure for cleaning to 30PSI or less for this reason.

This is taken from a piece about a different type of airgun, but the concept still applies:
"Due to the serious injuries than can be caused by compressed air, OSHA requirements pertaining to the safe use of safety air guns for cleaning purposes focus on pressure and chip guarding. The federal OSHA requirement can be found in 29 CFR Part 1910.242(b), which states: Compressed air shall not be used for cleaning purposes except where reduced to less than 30 psi and then only with effective chip guarding and personal protective equipment."

Again, I think what you've built is brilliant, but seriously, stop using it. I think you'd be better served by getting a slingshot than firing this gun that you've made. You can move a bigger projectile, faster, and more accurately.


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Man I hear what you say, and I know about the water not storing energy as I used to build water rockets, and I would use water to pressure test splices so if it failed it wouldn't be a bomb. However I do have a few years experience building these and I've taken proper precautions with these guns. :)

The pressure vessel inside the gun is encased in an armor shell.

It's also not a huge reservoir.. Only ~12 cubic inches. And I'm only operating at a bit more than air compressor pressure. I usually use a shock pump.

I wish I could get a real airgun, but my dad just won't let me yet.

And I just have to say, I have a slingshot and it's not nearly as fast. This gun can shoot THROUGH cinder block and keep moving, A slingshot can't.
 
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USABRO, maybe it would also be interesting for you to find out with how much of a TNT equivalent you are dealing while filling/handling that PVC airtube :)

The link below might help you to calculate and maybe reconsider if to move further with those engineering experiments, which are of course cool, bet VERY dangerous considering your current experience and the matherials you are dealing with (tip: a normal hand grenade has about 150 grams (0.33 pund) of TNT). 

http://www.nigelhewitt.co.uk/diving/maths/tank.html
 
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