SpudFiles

So my big plan in terms of projects is a HPA backpack and good all round BB gun [that can shoot both airsoft and steel BBs].

I already know what i want the BB gun to look like, but i have come to an intersection and i do not know which way to turn!

What are the pros/cons of having a QEV added to the BB gun?

NOTE: The gun WILL be regulated. Max pressure being used will be 500psi.

NOTE: If i eventually just get fed up with having to fiddle with nasty little spray guns [i only like them because of the shape, makes it easy to work with] i will just make something like this:

The QEV will hold more pressure and exhaust will be faster but the second one would work but i think 500 psi would rupture it, im not sure maybe if you have a 500psi blowgun.

The only issue with using a QEV like that is that the QEV will not close when you let off of the trigger. Using a modded blowgun for bb sized projectiles is plenty.

Mod the QEV for chamber filling. It can take the pressure. The QEV will be way more powerful.

You don't need a QEV if you use a detent

I agree, a detent is SO that way to go.

Gun Freak wrote:I agree, a detent is SO that way to go.

The problem with airtight detents is the whole jamming-the-barrel-with-the-second-BB-before-the-first-leaves-the-muzzle issue, some sort of blocking bolt would still be ideal, or you can go for a non-sealing mechanical detent:

Interruptor

I believe I'm having the same problem on my valveless (still ) but that's only because you haven't came up with a solution

On the drawing board

jackssmirkingrevenge wrote:On the drawing board

When are you not?

Gun Freak wrote:When are you not?

No no I'm at work, the design is on the drawing board

but i think 500 psi would rupture it, im not sure maybe if you have a 500psi blowgun.

This model of blowgun is actually a spray gun, and can take 800+ psi ;D

Detent aye? Sounds good. Questions:

1. Does the detent increase the velocity of the projectile? Because it has to gain more direct pressure to leave the barrel.

2. With a bolt and spring operating the detent, what would be the effect of loosening or tightening the spring be?

3. How do O-ring detents perform under automatic fire? of steel and airsoft BB's?

Pneumaticology wrote:1. Does the detent increase the velocity of the projectile? Because it has to gain more direct pressure to leave the barrel.

Yes. The idea is that you adjust the detent to release the projectile only when a minimum pressure is reached. This way, it doesn't matter how fast your valve is, you will always get maximum performance in terms of muzzle energy.

2. With a bolt and spring operating the detent, what would be the effect of loosening or tightening the spring be?

The tighter the spring, the more energy and time the projectile needs to overcome it, so it will increase muzzle energy and reduce rate of fire.

3. How do O-ring detents perform under automatic fire? of steel and airsoft BB's?

See for yourself

Airsoft works great but unfortunately with slower heavier projectiles, there are issues where a projectile might not have left the barrel before the next one goes into the detent. This can have the effect of actually stopping the first projectile in the barrel - at best this reduces performance, at worst:





There are some ideas to avoid this, need to be refined though. This should work for semi auto:



This on the otherhand only blocks flow when the chamber is pressurised, so technically should cycle full auto:

What about this JSR?

Pneumaticology wrote:What about this JSR?

that could work but wont be very powerful because the next bb will block all the flow.