are this fast enough??

[SP00K]

As said before, I'm just being obnoxious.

[Ragnarok]

WTF, he must be a British invention.

As a general rule, given this is such a large, and international forum, avoid saying things like that.

We have the odd lighthearted joke where we assign a not entirely untrue trait to a country (like the tendencies of our Australian members to on occasion, be noticeably more zany than the rest of us), but assigning a country to a negative trait is a no.
And I'm not saying that just because I'm British, I'd be advising you against it regardless of which country you'd picked.

and i see the last reply not connected to the question that i asked

And you're surprised? This forum does that all the time - if you've got a problem with it, you're in the wrong place.

It's also not on to be trying to scold D_Hall, who has done far more for spudding than you are ever likely to. I suggest conducting a forum search for the acronyms "GGDT" or "HGDT", internal ballistics simulators which can be found on the computer of any truly serious spudder - or that they wish were on their hard-drive.

fast enough to let the compressed air get out from the chamber

Like MrC says, that could be accomplished with a flow over several hours, days or even weeks.

will it is a small bore gun 8mm .lets say is not a canon
and the pressure is 700 psi and i think about 1500 psi

If you have to ask if a valve like this is "any good" for a purpose like that, you certainly do not have the experience and knowledge required to safely use pressures anywhere near that high.

Seriously, scrap any plans you have that will use those pressures, at least for the foreseeable future. Anyone in your position shouldn't really be using more than 150 psi, and even that I have to say is somewhat on the optimistic side.

[TurboSuper]

I'd say it ranks somewhere in between hand-actuated ball valve and modded sprinkler valve.

With a high pressure and a long ass barrel, opening time will be less significant.

[psycix]

Besides opening time, a spring loaded ball valve can be a way more comfortable trigger.
Slapping open a BV throws of your aim.