My QEV+Slide Valve multishots

[encohen]

--------------any suggestions would be appreciated----------
Hey guys,


All the info is in the video if you're to lazy to read

So i've been working on a new PCP, my main goal was to get more than one shot per fill while maintaining power and accuracy. What I came up with was a 48" long QEV and Slide valve air rifle with a 25" 14mm diameter barrel.
I tried to keep the build on the cheap side so other than the the QEV & Slide valve from ebay i used what i had or found.

It's got a 600cc air reservoir that i got from an old soda stream machine, the reservoir is connected to a tee with a schrader valve. on the other side of the tee there is a 1/2" QEV (modified with a spring) with a 1/2" slide valve as a pilot valve. the QEV air port is connected to a 1" diameter 20cm long plumbing tube (which gives me around 100cc of volume). last, the output port of the QEV is connected to a 14mm diameter, 25" long aluminum tube that i have found. Ration beetween the air reservoir and the firing chamber volumes is 1:6 (in favor of the air reservoir )

the performance from this rifle were better than i expected: First, it's really comfortable to shoot. I get 5-7 good shots with one fill of 160 PSI (that's as high as my bike pump can do) , it's really accurate (so far i've only fired it from up to 25 meter away) , and it really powefull, more the enough from small game.


Improvments for the future:

- replacing the shredder valve with a quick disconnect valve so i can pump more pressure with a PCP pump
- replacing the barrel with a 10mm diameter barrel so i can shot 10mm bearings with it (didn't find any bearing that fits this barrel)
-making a magazine for it.

Video:

[youtube][/youtube]

[jackssmirkingrevenge]

Great job!

I get 5-7 good shots with one fill of 160 PSI (that's as high as my bike pump can do) , it's really accurate (so far i've only fired it from up to 25 meter away) , and it really poweful

160 psi is relatively low for small calibers, if you manage to go to higher pressures it will really be a revelation as to what the power potential is. If I were you I would consider getting a paintball HPA bottle that will give you a regulated power supply for more consistent shots.

A Ninja tank like this one has an adjustable regulator that can be dropped to about 450 psi output, and you would be able to fill it with a PCP pump (and give yourself a good workout!).

replacing the barrel with a 10" diameter barrel so i can shot 10mm bearings with it (didn't find any bearing that fits this barrel)

If you're interested in usable accuracy, this is the way to go in the circumstances, but make sure you get proper bearings and not something sold as 3/8" slingshot ammunition to make sure the diameter and shape is consistent.

[encohen]

Thanks jackssmirkingrevenge, much appreciated!

A Ninja tank like this one has an adjustable regulator that can be dropped to about 450 psi output, and you would be able to fill it with a PCP pump (and give yourself a good workout!)

Yes, I was thinking about getting something like that, it would help me with capacity, acuracy & power.
the only thing is - I'm not sure what diameter the threads are on these kind of tanks, and how will I connect it to the rest of the rifle. I've read somewhere that most paintball tanks comes with a 5/8"-18UNF threads so i can probebly get an 1/2" BSP to 5/8"-18 UNF adapter. I'll give it some thought. that would make a serious upgrade!

If you're interested in usable accuracy, this is the way to go in the circumstances, but make sure you get proper bearings and not something sold as 3/8" slingshot ammunition to make sure the diameter and shape is consistent.

Yep, i got some 10mm bearings balls (1000 grade) of ebay & a 10mmX65cm blowgun from a local shop to be used as my new barrel. hope to get them by next week, I'll post a new video when I do .


I was wondering . will pumping more pressurre will result in more shots per fiil or just more power? meaning, without getting a paintball tank.

and one more thing, i found a second hand paintball (m4 replica) for sale on the cheap side. thinking about buying it and mybe converting it to shot bearings, not sure what cal are paintball and if it's possible. but if it is, I'll get full auto

[jackssmirkingrevenge]

the only thing is - I'm not sure what diameter the threads are on these kind of tanks, and how will I connect it to the rest of the rifle. I've read somewhere that most paintball tanks comes with a 5/8"-18UNF threads so i can probebly get an 1/2" BSP to 5/8"-18 UNF adapter. I'll give it some thought. that would make a serious upgrade!

5/8-18 is the actual bottle thread, to use the regulator you need an ASA thread.

This sort of part for paintball guns will give you a socket for your bottle on one end and a 1/8NPT connection on the other, not difficult to find for cheap:

will pumping more pressurre will result in more shots per fiil or just more power? meaning, without getting a paintball tank

Power. Double the pressure, you double the force pushing your projectile - that doesn't necessarily translate to a linear increase in muzzle energy, but that's the general idea.

and one more thing, i found a second hand paintball (m4 replica) for sale on the cheap side. thinking about buying it and mybe converting it to shot bearings, not sure what cal are paintball and if it's possible. but if it is, I'll get full auto

What brand and model is it?

[encohen]

5/8-18 is the actual bottle thread, to use the regulator you need an ASA thread.

This sort of part for paintball guns will give you a socket for your bottle on one end and a 1/8NPT connection on the other, not difficult to find for cheap:

OK, i think i got it. so using the ASA thread & a paintball tank with a regulator will allow me to connect the tank to the rifle and control the pressure.

**my soda stream tank can handle up to 3600 PSI and fits perfectly with a 1\2" male BSP thread, but i didn't find and regulator that will fit (and buying the extra adapters to make it fit isn't gonna be cheaper).

Power. Double the pressure, you double the force pushing your projectile - that doesn't necessarily translate to a linear increase in muzzle energy, but that's the general idea.

ok, so after a pressure upgrade i might make my firing chamber a bit smaller to get more shots. although, if i get a paintball tank with a regulator that won't be necessary.

What brand and model is it?

it's a Rap4 T68

[jackssmirkingrevenge]

1/2" BSP is the same as the ASA thread on paintball tanks, here's one in a 1/2" BSP ball valve:



You will however need a smooth surface inside the fitting beyond the thread for the o-ring to seal, and some sort of pin to open the valve on the paintball tank.

ok, so after a pressure upgrade i might make my firing chamber a bit smaller to get more shots. although, if i get a paintball tank with a regulator that won't be necessary.

For the same quantity of air, high pressure low volume gives significantly more power than low pressure high volume.

it's a Rap4 T68

A caliber change from 0.68" to 10mm is possible but it will be difficult to do it properly without access to a lathe, you will need to machine a new bolt and barrel fitting.

[encohen]

1/2" BSP is the same as the ASA thread on paintball tanks, here's one in a 1/2" BSP ball valve:

just making sure I got this right: theoretically speaking, can I order this: http://www.ansgear.com/Ninja_Compressed ... ank-48.htm

and simply connect it to 1\2" BSP tee?

A caliber change from 0.68" to 10mm is possible but it will be difficult to do it properly without access to a lathe, you will need to machine a new bolt and barrel fitting.

Yeah I think I'll give it a pass

BTW: tnx for all the help

[jackssmirkingrevenge]

just making sure I got this right: theoretically speaking, can I order this and simply connect it to 1\2" BSP tee?

In as much as they have the same thread size, yes, but there's a caveat, paintball fittings have certain attributes to mate with bottles:

In order to use it with a plain BSP fitting, you would have to put thread tape or sealant to have the bottle permanently fixed to the launcher, and you would have to remove the bottle valve.

[encohen]

I'm getiing all excited here. I'm thinking of getting a CGA 320 Adapter like this
http://www.ebay.com/itm/CO2-Paintball-T ... Sw9N1V1vUQ
and a air tank + adjustable regulator like this: (maybe I'll look for something a bit less bulky)
http://www.ansgear.com/Ninja_Compressed ... ank-48.htm

and than i could have a serious setup with more shots per fill, more power, and better consistency & accuracy!!

BTW JSR: how do you link text to URL here? srry, I'm a newbee :bounce:

[jackssmirkingrevenge]

You can get something like this, less than 30% of capacity but more compact and lightweight. I recommend Ninja as a brand because their regulator output is relatively easily adjustable by adding or removing shims.

how do you link text to URL here?

For what I wrote above it looks like this:

(url=

Just use square brackets instead of round ones.

[encohen]

JSR, I got one more question for you..

For the same quantity of air, high pressure low volume gives significantly more power than low pressure high volume.

is that still true if my firing chamber (the reservoir connected to the air port on the QEV) has a smaller volume than my barrel?

[jackssmirkingrevenge]

Yes, as long as barrel volume is less than ( chamber pressure ÷ 15 ) x chamber volume.

Consider this little exercise I had done with a virtual 0.177" BB launcher - in each case, the amount of air is the same, but at each step I half the volume and double the pressure:

20 inch chamber at 50 psi - 406 feet per second - 2.82 ft lbs

10 inch chamber at 100 psi - 537 feet per second - 4.93 ft lbs

5 inch chamber at 200 psi - 684 feet per second - 8.00 ft lbs

2.5 inch chamber at 400 psi - 830 feet per second - 11.78 ft lbs

1.25 inch chamber at 800 psi - 958 feet per second - 15.70 ft lbs

0.625 inch chamber at 1600 psi - 1006 feet per second - 17.31 ft lbs

You can see from the energy figures that if power is your goal, it's in your interest to use as high a chamber pressure as your fittings can take.

[encohen]

Yes, as long as barrel volume is less than ( chamber pressure ÷ 15 ) x chamber volume.

Ok, so i'm trying to design a new air gun with a 10mm, 25" long barrel, connected to a 1/2" QEV & Slide valve, with a 1/2", 4" long air chamber. I intend to connect the Slide valve into a 500PSI air source (Paintball tank with adjustable regulator)

but...
I inserted the data into GGDT and I get some strange results, the muzzle energy & velocity are really low and there is a barrel choke warning . what am I doing wrong?

[jackssmirkingrevenge]

You missed changing the valve and projectile data, try with the following:

Projectile Mass: 4 grams

Valve Type: Barrel Seal

Seat Diameter: 0.5

Piston Mass: 0.3

Piston Diameter: 1

Vent Diameter: 0.1

Pilot Volume: 0.15

[encohen]

Tnx JSR, I found a software info in the GGDT link you gave me