low range and fps with vortex gun

[Tusken Raider]

Ok, I made an inline bullpup vortex airsoft cannon. Full block, fires around 3000 rpm from a 160 psi tank. Compressed air. Gun is 1.5 inches in diameter, 18 inches long, with a 24 inch aluminum barrel.

Feeding issues: the block was too wide, solution was to grind down the block's sides to allow unobstructed feeding space.


Here is my only issue: I cannot get this bad boy to fire more than 40 feet. And at a very slow muzzle velocity of 200 fps or less. I know I may be being too positive in my thinking, But I want this sucker to pack a punch at 100 yards or even 75 yards at least.

Any suggestions?


I have built several tater guns that fire nerf footballs and beehive rounds out to and exceeding 100 yards+. So I know a bit about what I am doing. Vortex guns are new to me, so I do not know anything except the concepts.

[noname]

Make the block out of something better, get a tighter fitting barrel, post pictures of it.
Try making an inline block for your next one, they're more compact, and they look and perform better.

[medievalman]

Where are you noname?

Well, from my experience, I know that the higher the pressure, the greater velocity and distance, but this is not the problem in your case, since you are already using 160 psi.
Another thing that could be affecting it is the length of the barrel. If you make it longer, the bb's will probably go farther, but it seems like you already have a long enough barrel.
One thing I am Uncertain of is how you are feeding the air into the gun. Is it a blowgun? If so, it may have a nozzle on it to restrict the airflow to about 30 psi or so. You can mod the blowgun to increase the airflow(look in the wiki) You could also use a ball valve for extremely high flow.

Can you please post some pics and specs on your gun so that we can help you better?

[Tusken Raider]

Thanks forgot to mention, the block is delrin (I splurged after reading these forums). pics will be up tomorrow.

[medievalman]

Okay, but what I want to know is if you're using a blowgun to "inject" the air! If not, what are you using?

[Tusken Raider]

A blow gun from home depot. It will drain the tank relatively quickly. 10 gallon from Lowes. I had thought that maybe the flow rate on the blow gun is way too low. But it will drop tank pressure from 160-80 psi in about 15 seconds.

Almost all fittings are 1/4 inch brass. I have 2 compression fittings with poly lines rated for 200 psi.

I have even so far as to try and use a regulator adjusted for 80psi output and a accumulation tank (1 pound approx), then into the air cannon. I used this after I was getting low range and fps.

I am going to polish the barrel with polishing compound tomorrow.

The only other thing I can think of is that the barrel may be distorted and it is causing friction on the bbs.

I stress, I have no jams, and with that fire rate I am sure it is getting enough air. So blowgun, I will try to replace with a ball valve.

And I will get pics posted asap

[Tusken Raider]

oh and no nozzles since it has brass fittings on it. Or would it be internal to the blowgun?

[Insomniac]

Edit your posts instead of double posting.

Do the bb's fit the barrel well?? or are they pretty loose?? Thats the only thing I can think of (don't know a whole lot about vortex guns)

[Tusken Raider]

they need only light pressure to exit the barrel. Sometimes they do roll out, but that is with the very very cheap bbs.

[benstern]

What type of barrel are you using?
commercial barrel?
Brake line?
custom?

[Tusken Raider]

standard aluminium tube. It was put on a lathe to trim it down at the receiver end to fit tight into the vortex block.

Maybe changing out to brakeline?

[benstern]

Yes, change to brakeline. It preforms much better.

[CpTn_lAw]

brakeline is for .177 BB's...
The must, and i keep on telling this, for airsoft barrels (6mm) is the 8mm OD copper pipe. 6,02mm ID is an almost perfect fit for BB's, 1meter length takes 20 seconds to go down .
Buy some, you won't regret it, you have my word.

[jackssmirkingrevenge]

To maximise performance, use as long a barrel as possible and eliminate all the dead space in the BB reservoir. You can do this by having the BBs already in the pressurised chamber, passing through a ball valve through the barrel like so:

[Tusken Raider]

Yeah the resevoir is being changed out to only 10 inches long this coming week. I just need to get off my butt to do it Yeah my barrel is something like 6.06 or something like that. Loose in other words.

Brake line it is. Been hectic busy this moring so I still have to get pics done as soon as I get my basement cleaned up.