Help, Airforce Tank Dumping Air
Hi guys,
Help please. Just bought a brand new spare high flow airforce tank and valve. Fitted Tony’s high flow top hat which is also new and unused and pumped it up. Fired great three or four times then dumped all its air. Frightening. So I put it back on the scuba, pumped it back up, fitted it back on gun and first shot did the same, this time blasting the silencer off the gun!
Help please. What do people recommend. Tony has a fantastic reputation and his stiuff is amazing so I’m sure it isn’t his tophat but just to rule something out I’ve fitted the high flow top hat it came with. As I say I know its not the top hat anyway. What should I do guys. I really don’t fancy it happening again.
All Replies
Viewing 9 replies - 1 through 9 (of 9 total)
From what I understand, this happens when the tank releases too much air, too quickly, creating back pressure and holding the valve open, until all the air is gone. Try adding an o ring behind the tophat. Getting a .25 barrel might help, but trying the o ring is a more cost effective route.
Tony I just tapped it in against a piece of wood until it felt seated. Compressing all the way to brass so must be seated? Should I have followed a procedure?
Right I’m really grateful for the lightning responses, I owe you one guys. As you can imagine I’m pulling my hair out. So Doug if I had the 25 calibre I’d kill the problem??
I want to kill the problem for good. Its no good it happening once a month or something. I did think it felt like it was making a lot of power in the three shots before it let go. Felt lots of recoil. So maybe the top hat is travelling in too far?
22 calibre, 24 inch. I’ve just taken it out Tony but the clearance looked about right to me, about a cm? I’m more concerned the tank stops dumping. I’ve fitted a standard top hat which looks slightly shorter. I was wondering what else I should do. I really want to stop it before it damages my gun. Its a brand new tank, brand new everything including your top hat of course.
You need to put a shim behind the tophat to limit how far it goes. Make the shim so you have .100″ gap to start. You might be able to go a little bigger. Mostly you will just be wasting air if the gap is to big. You can also go smaller also.
Tank dump is a problem with .22 and especially .177. It is because the barrel is diameter is .308″ and the hole is .22. With .25 the is no issue because the barrel is real thin. With .177 it is worse because the barrel walls are thicker giving more resistance against the valve.
Once the valve is held open to long you get tank dump. Some times a partial dump or sometimes a full.
I had all kinds of fun building the .308 valve. It does the same thing. Right now I have a .070″ tophat gap on .308 and it still can make 300 fpe. .257’s don’t have a dump issue but still run a shim to set it at .115″. Any thing bigger and it is just wasting air with really no gain
What caliber and how did you seat the valve stem into the seal?
How much clearance from bottom of top hat to brass insert?
Thanks, Tony
What caliber barrel you are using? Some time bad seating of pellets also cause tank dump… :sadn:
I’m waiting for hopefully the stream of helpful advice before doing anything now. The last dump was so violent I lost my zero on my scope and it bruised my face 😥
Viewing 9 replies - 1 through 9 (of 9 total)
- You must be logged in to reply to this topic.
Thanks TheHunter. Yes the o ring is definately the cheaper option. 🙂