Consistency and the XValve

[TAC-ELF]

Forgive me if I'm showing my newb-ness, but something just sunk in about how the XValve works and its bugging me a little. Please, I'm not trying to say the XValve sub-par or anything like that and I'm not trying to insult anyone.

I was just reading the page on Chrono-ing my first 'Mag: Brand new Tac-One. Paraphrased it says something along the lines of:


"With a X-Valve you fire a shot, hold the trigger back and quickly release a shot over the chrono. This simulates rapid firing. Since the valve recharges so fast, it should be tested this way. To test a X-Valve like a normal valve would give you incorrect readings."

This appears to be saying that if I take more than a few milliseconds to fire the next shot, my velocities will be off by a considerable margin and not necessarily predictable.

Am I reading this right? Remember, I'm a newb when it comes to 'Mags and this is very perplexing to me. Obviously the design is temperature sensitive -- but in this case due to not the outside temperature, but the temp of the air inside the gun. This is something I thought I left when I got rid of all my CO2 gear (though it is the opposite case for CO2).

I understand why the temp sensitivity is there -- friction builds up in the charge as it fills the regulator. However, as the temperature drops shouldn't the charge in the reg be filled back up to its proper pressure?

[ScatterPlot]

You know I never thought about it that way. I'd be interested to hear some other comments on this as well, but here's my take-

I think that the odd chronoing procedure takes care of velocity spikes, and the spikes aren't as far out as you'd think- this is pure guessing, but I might guess somewhere in the range of 3-4 FPS. I think it's just so that you don't chrono at 298 on a cold gun, then after a game get hit for doing 303 or something.


But that's a complete guess, someone back me up/shoot me down here.

[Severe]

I'm definitely not an authority on this, as I too have recently picked up a Tac-One and my first X/RT style valve. But I understand exactly where you're coming from.

I may be a bit biased here, since I've shot a classic valved mag for the last 5 years and really moved to the Tac for the body, but I think my classic valve is a better product.

It can run on C02 or HPA, it's more consistant across the chrono and I personally can not outshoot it. (I forget at which point it starts to experience shoot-down). Then again, I'm not trying to get 15+bps either. If I wanted to do that, I'd use a different marker.

I do love my Tac-One and X-vlave, but I think I would have been just as happy with an aluminum classic valve.

[TAC-ELF]

You know I never thought about it that way. I'd be interested to hear some other comments on this as well, but here's my take-

I think that the odd chronoing procedure takes care of velocity spikes, and the spikes aren't as far out as you'd think- this is pure guessing, but I might guess somewhere in the range of 3-4 FPS. I think it's just so that you don't chrono at 298 on a cold gun, then after a game get hit for doing 303 or something.


But that's a complete guess, someone back me up/shoot me down here.
Just to clarify, I'm not really worried about how to chrono the gun. My bigger concern is how this variability affects the consistency of the marker during game play. I'm not the kind of player who tries to shoot as fast as I can all the time. Rather its a mix of fast shots and slower, more targeted shots.

On the field, when I shoot fast I get (276 - 284fps) but a significant drop if I wait for awhile before I shoot again (261 - 275fps). This is normal?

--TAC-ELF

New Tac-One
Level10: 2 shims, largest carrier that doesn't leak
ULT: 2 shims
PMI Premium paint
Stock barrel

[11 Bravo]

I think as the valve and regulator break in they become more consistant. I have noticed that my new Xvalve has gotten more consistant and maybe more efficient.

[Dead Eye]

I'm with 11 Bravo on this one.

Irecently bought a new Tac One myself, and seem to remember something about a break in period for the valve. I can't remember the numbers right off hand, but I think it was either 200-300 rounds or after the first case of paint, everything should be seated correctly.

[PumpPlayer]

If you read the entire article which you speak of, you'll notice that the input pressure has a large effect on this feature of the RT valve (or X- or E-, they're all the same). Bottom line, if you're running your high-performance valve on a pre-set screw-in tank, you're not getting the full performance out of it. Would you put low octane fuel into a Ferrari?

Low pressure, you'll get shoot-down with rapid firing and with high pressure you'll get spikes. You should get a chrono and adjustable tank and set the input pressure where the velocity remains most consistant. 'Mags will easily do +/- 3 fps with good paint, proper bore size and correct input pressure.

[TAC-ELF]

If you read the entire article which you speak of, you'll notice that the input pressure has a large effect on this feature of the RT valve (or X- or E-, they're all the same). Bottom line, if you're running your high-performance valve on a pre-set screw-in tank, you're not getting the full performance out of it. Would you put low octane fuel into a Ferrari?

Low pressure, you'll get shoot-down with rapid firing and with high pressure you'll get spikes. You should get a chrono and adjustable tank and set the input pressure where the velocity remains most consistant. 'Mags will easily do +/- 3 fps with good paint, proper bore size and correct input pressure.
Well, I've put about 3000 rounds through it and see little difference between brand-spanking-new and now. Sure, I'm using a 850psi pre-set tank -- it is pretty much the standard starting point for most folks -- but I'm very soon getting an adjustable reg (Max-Flo).

So which way should I go? Up-pressure or down, based upon everything I've said so far? Don't think I'll ever hit even 15bps: I just cannot trigger that quickly...

--TAC-ELF

New Tac-One
Level10: 2 shims, largest carrier that doesn't leak
ULT: 2 shims
PMI Premium paint
Stock barrel

[athomas]

When a retro/xvalve recharges, it does so quickly that the air heats up. The heated air is the regulated pressure in the chamber. If you immediately fire the gun, you will get a velocity reading on the ball pushed out the barrel by that regulated pressure. If you wait a moment, the air cools and the chamber pressure will drop a few psi. Now, if you fire the gun, the velocity reading will be lower due to the ball being pushed by the lower chamber pressure.

The amount of heat generated is very much a product of the rate of recharge which is a result of the pressure differential between the the tank and the operating pressure of the mag chamber. The level 10 equiped retro mags have less velocity fluctuations than level 7 equiped retro mags due to the level 10 having a higher operating pressure in the chamber.

The end result is this. For safety reasons, chrono the retro/x valve using the recognized chrono procedure. Pull the trigger and hold it. Next, fully release and then pull the trigger, usually in one motion. This will give the maximum velocity that the valve can achieve under normal operating conditions (normal ball,barrel,gun fluctuations not considered). Normal single shot firing will be consistent and less than the chrono velocity. Under rapid fire conditions, you will notice an increase in velocity up to the chrono velocity but not above it.

Depending on your setup, the chrono procedure velocity will only vary a few fps above the cold single shot velocity. For some it is higher, some it is lower. On my setup, it is hardly noticeable.