Air Gun Home :: View topic - Custom Air Rifle Build (I hope this works!)

TheAznInvazn · Member

So, paintball is what I know best as far as pneumatics go, and after looking at some various PCP air rifles, some work off a very similar design as some paintball markers, namely being a hammer striking a poppet valve open.

So, I'll be chopping up the body of a paintball marker, only utilizing the parts that house the pneumatic parts, and hopefully I will get it shooting!

My plan is to chop the top tube off, and use the hole in the body that connects to the poppet valve and attach that port directly to the air rifle barrel

After getting all that done, I would love to put it in a cool stock, and after looking around the new for stocks, I was thinking, I could probably get a pretty good stock off an airsoft gun for a decent price!
WELL MB05 AWM APS2 Airsoft Sniper Rifle - MB05 Airsoft Sniper Rifle - AirSplat.com - AirSoft Gun Warehouse

I'm planning on using this, and this site has it the cheapest (as far as I could find)
Hopefully I can also use the barrel shroud, trigger, and possibly the bolt action from this as well!

I have a good feeling about this!

As for the reason I would like to do this build, my old .22 cal pump air rifle finally broke its main pump seal, and with it being older than I am, it would be very difficult to get it fixed (an old S&W air rifle). So, I plan on taking only the barrel from the broken air rifle, and making the rest of it from paintball/airsoft parts so that I can take it to our property and not freak out the neighbors! For those of you who do not shoot, or do not shoot regularly, you would be surprised how loud the humble .22LR is!

So, any thoughts on the build?
And what pressures to PCP rifles usually work off of?
I know I've seen a few that use 13 and 22 ci air cylinders, so is that directly attached to the rifle, or is there a secondary regulator to bring down the pressure even further?

Alstone · Moderator & Site Supporter

PCPs run around 3000 psi and there is no regulator between the bottle and PCP tube, I think you may find that paint ball stuff will not handle the pressures you want.

Someone who knows a bit more about it than me will be along soon.

Welcome to the forum.

Al

TheAznInvazn · Member

Is that so?
I saw a picture on a different thread with what looked like a regular paintball cylinder
http://www.airgunhome.com/agforum/viewtopic.php?t=6360

Do they not have a regulator at the top?
If this is so, than I may have to rethink my approach

AirGunEric · Site Admin

The bottle in the other thread has a regulator- it can often be found as a "Paintball HPA tank"- and is normally regulated to 850psi output- which your paintball-marker parts can handle. Change the output pressure to something higher and perhaps the marker frame won't be able to take it- I believe Al was hoping to underline the idea of "better safe than sorry"- and keeping that in mind- as long as you leave a/the bottle at 850psi, you're likely fine.

TheAznInvazn · Member

Ah, thanks for the clarification!

I do intend to keep everything in safe working pressures, though the raw strength of the parts in the paintball marker I've chosen can handle well over 850 psi

In any case, I plan on getting a 13ci 3000 or 22ci 3000 HPA tank to power this project, and maybe a remote line and my current 4500psi tanks if I get trigger happy
Smile

So far it seems like my idea still has a chance!

shawnhu · Member

Regarding safe pressures and trajectory of airguns vs paintball guns:

Some airguns are able to achieve 900 f/s of a 18 grain pellet using in the upward of 2000-3000 psi.

The speed at which a paintball can be propelled up to 300 f/s from as low as 180 psi.

Most paintball barrels only require about 6 inches to accelerate the paintball to those speeds. Since the length of a pellet rifle barrel is much longer than that, we can expect more acceleration from the 180 psi of that a paintball. I don't know the weight of a paintball off-hand, but I'm willing to bet it weighs more than 18 grains. We'll gain some more speed there as well. With that said, I think it's totally possible to shoot an 18 grain pellet with a paintball marker set-up at 180 psi. Now let's increase that pressure to 800 psi, which most paintball markers can handle with no problem. That's about 4x of 180 psi. 500x4 would be in the 2000 f/s range, if my rough calculations are correct.

I definately would LOVE to see a maintball marker conversion to pellet rifle. For the simple fact that there is a paintball marker out there that is capable of autoloading pellets on a semi-automatic basis. This is the WGP Autococker. With the help of the Eclipse Blade, the e-trigger would be a beautiful pellet gun, nothing the pellet world have ever seen before. An electronic trigger with nearly 0 weight, and no first stage.

Very excited in seeing what you come up with.

TheAznInvazn · Member

I'm feeling good about this project now!
I was also thinking that I will be able to adjust the dwell time to increase muzzle velocity of need be

While I don't have any plans for a auto loading pellet rifle at the moment, if this happens to work, that maybe my next project!

SMP · Silver Status Member

I think your on to a fun build and I can't wait to see the result.

Yes 850psi will drive a pellet no problem but you will max out at around 650fps not 2000. The area against which the force is applied means everything and a painball has exponentially more area that a pellet. Not to mention a few physics principals like absolute mass flow and choked flow.

Autoloaders and e triggers have been around for years in the pellet gun world. They are not well loved though. Pellets are very susceptible to damage by a loading mechanism and don't feed nearly as nicely as round balls.
Feeling a first stage and knowing there is a crisp break immediately after makes a rifle more accurate.

rsterne · Moderator

The link you posted is my Hayabusa, and that 22CI tank has a regulated output of 1900 psi, not 850 psi.... All the rest of the gun is designed for a safe working pressure of 3000 psi with a 4:1 safety margin....

Before you start modding a paintball gun to work at those kinds of pressures make sure you know what you are doing.... we don't want to read about you as a statistic....

Bob

TheAznInvazn · Member

Well, the longer I can keep the valve open, the more air I can force down the barrel, and with an electronic solenoid, I can do just that!

As for trigger pull, I was thinking about this as well, and again, my experience is paintball.
I can place a magnet on the trigger, and a magnet somewhere else on the trigger mech in such a way that they are attracting each other, keeping the trigger in the ready position. As soon as enough force is applied, the magnets will "break" apart crisply with little to no creep at all. I will place the microswitch somewhere that the trigger can actuate after the trigger pull.

I have big plans for this, and I think that this will turn out well!

~edit
Wow, that's a lot of pressure!
Well, there are three ways to get the desired velocity out of poppet valves as far as I know. One is high pressure, so that once the valve is open, a large amount of air passes though the valve. Second dwell time, the actual time the valve stays open. Even with a relatively low pressure, if the valve stays open as long as the pellet is in the barrel, I can maximize the air pressure I have behind the pellet. Third is a combination of pressure and dwell time.

Still feeling pretty optimistic about this!

AirGunEric · Site Admin

It doesn't matter how long you hold a valve open if the projectile is already out the muzzle- at that point you would merely be pissing the propellant into the air.

And as for the post about using 180psi to push an 18gr pellet out a barrel- please see SMPs comments- the response indicating this would be a possibility using airgun pellets was grossly mistaken.

TheAznInvazn · Member

Indeed you are correct that if the pellet is out the barrel, than keeping the valve open would only waste air and ruin efficiency

As for the pressure used to shoot the pellet, I think I can get a bit past 180psi if that's the problem
All the seals are mechanical, nothin really delicate to overpressure and destroy, and nothing that a few orings can't fix.

Also not aiming for 2000fps
This is more along the lines of a proof of concept/fun build/not wanting to buy something that everyone already has! This is purely for my own satisfaction and learning, and if this happens to turn out wonderfully, than I may have to do more complex versions. If it fails miserably, I guess I'll just go out and buy a nice air rifle...
Smile

SMP · Silver Status Member

??? Just for my own personal interest

When you run a paintball gun on HPA what reg pressure do you use?

TheAznInvazn · Member

Well, to shoot at a safe velocity (under 300fps) it can be anywhere from about 850psi (direct pressure from tank reg) or anything as low as 150psi

Things like Spyder's and Tippmann's like unregulated CO2 or straight 850psi from HPA tanks, other markers that have sensetive solenoids and whatnot can use lower pressures due to the way they're made and such

NZ Shooter · Suspended

Hoooooolyyyyy S*****t. Come on, fella, back the f#ck up. Seriously, pardon the swearing, but dude, DO NOT try and use paintball marker internals at the pressures you are wanting to. Modifications cannot be taken lightly. Don't lose an eye, or your life for the sake of ''experimentation''. "Go Hard, But Don't Die Doing It''