2k9 Micromag Veloctity Issues

[WarHamster]

Okay, so I've been playing around with my 2k9 Micromag, and I am having trouble getting it to shoot above 250 fps. I've done my best to eliminate every variable and as near as I can tell the Micromag body itself has to be the culprit.

I've tried two X-Valves, an RT Micromag valve, and an EMax valve. In each valves case I turned the velocity up as far as I could before I started to get leaks out the back, and I've never topped 240~250 fps. When I pull those same valves out and put them into any other body I'm getting 320~340 fps.

I've tried several frames (a CF single, a powerlyte, a stormwalk, and an intelli) and three sears on the micromag body as well and none of them have had any luck in raising the velocity.



So my question is this, what about the micromag 2k9 body could be causing the velocity drop? Furthermore, how can I compensate for or correct this issue, so I don't have to push my valves right to the limit just to get a usable velocity?

[Ando]

You try it out with a gold spring?

[WarHamster]

I tried the red and silver springs I had. I don't have any gold springs.

[Ando]

Hmm...You might want to talk to PTP about it then. The red spring should work with it. The silver not so much. You could always cut the silver down but I wouldn't recommend it. Save it so when your red spring wears out on ya.

Get with someone in your area that has a gold spring and see how it goes.

[athomas]

Interesting.

From a firing standpoint, a mag is just a chamber full of air that is released when the sear lets the bolt go. The velocity is determined by the pressure in the chamber, the tension on the bolt spring, and the length and bore of the barrel. If you are using the same valve, in another mag with the same bolt spring and same barrel configuration, then it should have approximately the same velocity. Make sure there is nothing interfering with the bolt as it cycles. Perhaps there is something different in the depth of the cavity between the front of the valve and the breach. This would alter the tension of the bolt spring.

[TwilightG]

I may be way off but just throwing this out there....

what kind of barrel are you using?
I had a moment last year when I forgot to put an insert in my DW fibur barrel. I could not get the darn thing to shoot over 220 until I realized what I was missing

[BigEvil]

I had noticed I had a break-in period with the MM2k body. It took about a tank of air for it to start working right. How does the valve fit? Is it real tight? Also, take out the bolt, and fit it in the body. See if it moves freely in the breech. Do it with the barrel on and detents in. Check the inside of the body and see if there is any rubbing on the top near the bolt.

[WarHamster]

Twilight. I used the same longshot barrel in all the testing.

B.E. I haven't tried checking the bolt fits yet, but I'll do that today. As for valve fit. The emax valve was a good fit, the two xvalves were snug, and the micro rt valve ironically was extremely tight.

[WarHamster]

I had noticed I had a break-in period with the MM2k body. It took about a tank of air for it to start working right. How does the valve fit? Is it real tight? Also, take out the bolt, and fit it in the body. See if it moves freely in the breech. Do it with the barrel on and detents in. Check the inside of the body and see if there is any rubbing on the top near the bolt.

So update time:

So I've already put probably 500 rounds through but I put another 200~300 through then tried firing it off some more with no luck. The velocity is still low. I tried pulling the detents out and single to see if they might be binding the bolt somewhat, but the velocity just dropped another 10 fps (presumably due to the holes in the breech).

When I manually was sliding the bolt around inside the body it didn't seem to bind anywhere and slid back and forth fairly easily inside of the body. There does seem to be some marking on the top inside of the body, but it looks more like tool marks that have been anno'd over then marring from the bolt dragging.

[DoubleDutch]

Hey any further updates on your velocity problems Warhamster? I just got around to firing up my 2K9 MM and I am having the same problem. I used an X-Valve, E-lowers, and barrel (Kaner kit) from a working setup, and I was getting around 210 FPS. Cranked it all the way up (hit the stop, no leaking, is that normal?), and I was getting around 250 FPS. It shot very loud at that point.

I have a black spring in there. Am I correct in that the spring discussion was to try to put a lighter one in there? The black spring feels lighter than the gold one I have.

Any chance that my barrel is not sealing in the breech? Some other way that the body is "leaking" perhaps?

[BigEvil]

Get yourself some of the small gold lvl 10 springs.

[sneakyhacker420]

IIRC, the Micromag uses a unibody construction, meaning that the rail it integrated into the body - could this be a problem with the on/off valve, on/off pin length, or sear?

It sounds like the valve is not being fully cycled - you may want to try getting a longer on/off pin for it, such as a standard RT Pro .765 length pin, as the standard pins are .750, and Emag pins .712

I've had issues where I tried to make my guns more reactive by swapping out the on/off pin for a shorter one (shorter = higher RT), but after a certain point, the on/off valve will not fully cycle because the pin is too short for the sear to it all the way. It will end up with erratic, low FPS, and sometimes a short stroking effect where the valve will just chaff instead of firing/cycling.


I know for a fact that is is not a problem with the actual valve, bolt, or spring length, as these are all standard dimensions for all AGD (and PTP) guns. It's definitely going to be something with the on/off and/or sear assembly, as the on/off pin length varies anywhere from .712 to .765" in length for different body and rail types.


-JR

[Ando]

The black spring should be the same as the gold one. I'm amazed you still have a black spring actually those haven't been made in MANY years.

As for sneakyhacker420 bringing the on/off into light...

I don't buy it but who knows

It shouldn't but the new body design is more then likely going to bring a few UNK conditions to the table that no of us have seen before. Sneakyhacker420 might very well be on the money with this one. Only thing to do now is exhaust all probabilities and that's to try it out with a longer and shorter pin. It could very well be a quark with those bodies due to tolerances.

Have any of you tried your valves in a different body to make sure the valve is tuned and 100% working as advertised?

ULT? You can get all sorts of pin lengths with a ULT.

[DoubleDutch]

I will try a gold spring, then it that doesn't work I can try a 0.75 pin (the only other length I have). It won't break anything will it?

I didn't know you could use an ULT on an E-Mag, that works too? Put it on there and start removing shims?

I pulled that X-Valve from a working E-Mag BTW. I have two other valves I could try too.

I will try all this as soon as the Shoebox pumps my tank back up.

[athomas]

The pin length shouldn't affect the shot velocity. It could affect the recharge rate or prevent it from cycling properly, but once the gun is sitting with a fully charged chamber, that shot should be only dependent on the pressure in the chamber and the parameters relating to the bolt. They would include the bolt spring and any tolerance issues that could slow down the forward speed of the bolt.

Try a valve and bolt installed without a bolt spring. Don't air it up. Hold the trigger and tip it back and forth to see if the bolt moves freely on its own.

Measure the depth of the body cavity where the valve sits. See if the depth from the breach face (metal retaining washer) to the lip where larger back section of the valve sits is the same as a standard mag body.

Measure the diameter of the hole where the bolt spring sits. If it is too tight, it could restrict the bolt spring from expanding outward and actually act like a stiffer spring.