Unusual RT Pro Issue. . .Now confirmed as micromag 2k9 problem!

[nak81783]

For the $8 or whatever they cost, I would order one. That way you get the right tolerances, material, etc. You could get another .750 on order, and start grinding down the one you have, unless you need your valve working for something else before the new part would arrive.

Anyway, I believe you would want to grind down the smaller diameter. However, I've never done it, so you might want to seek some consenting opinions first. I will measure my .750 and .712 pins tonight and let you know where the length variance is.


-Nathan

[sniper42]

I will try spacing the detents out and see if that helps. I haven't done the dykem yet but I will try that too. I will disassemble it and take it to work. We have full sets of precision guage blocks so can figure out internal dimensions of everything.

If I were to make a new shorter on-off pin to try, which side is shorter, the fat side or the skinnier side?

[nak81783]

Did a little more digging. Don't have the best news, as some people haven't figured there's out either. The solutions seem to be:

1. Remove detents to see if marker fires better. If so, I don't know where to go from there. Possibly add orings to move the detents out.

2. Remove breech to see if marker fires better. If so, possibly open up the bore of the breech some. More on this later.

3. Try an E-Mag pin (.712"). I read one post where an E-Mag valve worked in the MM2K9 body, but an X-Valve (.750" pin) did not. If it still doesn't work at .712, and you don't want to use it for anything else, you could continue to grind it down until it no longer seals the on/off when you pull the trigger in hopes of finding a magic length. One poster suggested asking PTP what length pin they recommend, but with the varying dimensions/results with these particular bodies, I don't know if that would help.

4. Did you try the dykem idea? If not, one poster said to blue up the ID, and install a Level 7. The Level 7 wouldn't vent when it hits something, so it would be more obvious where it's hitting. But if you're in the mid 200 fps range already, it's probably happening near the end of the bolt stroke, so you wouldn't hear the Level 10 venting.

5. If you have access to a Z-Cal and surface plate, CMM, Faro Arm, etc., you could check the true position between various circles in all the different bores. Back, breech, front. Not really familiar with these, so bear with me. In the end, you're looking for cylindricity, but that can be hard to measure without proper equipment. Knowing diameters along the length of the bore and true positions between those diameters will get you close. If you find something you think you could fix with the equipment you used before, without turning it into a hotdog (valve) in a hallway (body) situation, you might want to try. This was what I eluded to in #2.

Again, I don't know what all you have access to. It's really hard to come to a logical decision without data; the lack of data primarily driven by the seemingly wide tolerances/issues with these bodies. That said, I'm just throwing darts, or re-throwing darts others suggested.

Good luck!


-Nathan

[sniper42]

Ok so I think I have determined it is an issue with the body. I tried my buddy's 2k9 body and it has the exact same issue. I did some searching and came across this thread.

http://www.automags.org/forums/showthread.php?261354-Definite-manufacturing-issue-with-2k9-mag&highlight=micromag+2k9

My body has similar measurements. Basically the body hole is bored .150" farther than my classic mag body. So far, that is the only difference I have found. Now with my limited understanding of automags, if the body hole is bored farther, that would put less pressure on the spring equating to higher velocities. However, the exact opposite is happening. Does anyone know what the depth of the hole for the body is supposed to be?

[blackdeath1k]

Probably not. But that's an easy thing to check.

[sniper42]

Is it possible that my detents are causing enough friction to slow the bolt down and impede velocity?

[sniper42]

I have not. I suppose I should send them an email.

[audioSLAVE]

It is a 2k9 micro. I'm aware that some of those had issues with tolerances. Ill try some dykem and see if I can find any rubbing spots.

Alright, that's what I was afraid of. I hope you can get it figured. Did you contact PTP?

[sniper42]

It is a 2k9 micro. I'm aware that some of those had issues with tolerances. Ill try some dykem and see if I can find any rubbing spots.

[audioSLAVE]

What kind of Micromag body is this? I skimmed but might have missed this detail.

[nak81783]

I was expecting a shorter length on the Micromag body, not longer. F=kx, so adding a thicker shim (i.e. compressing the spring more), will put more force against the forward motion of the bolt, reducing velocity.

I'm running out of ideas, especially since the valve seems OK, and I have zilch for experience with Micromag bodies.

It sounds like you have access to machining and inspection equipment. Perhaps you could blue dykem the inside of the Micromag body to see if there is excessive rubbing/binding preventing the bolt from completing its stroke and/or releasing the air properly.


-Nathan

[sniper42]

Well that did the opposite of what I though it would. A thicker bushing, therefore increasing spring pressure, decreased the velocity. I took out the bushing all together and I had no problem getting it to 290 with a clipped spring I had in my toolkit. However being an aluminum body, I imagine it will peen over, over time. I am baffled because the valve works fine in the classic body.

[sniper42]

Just another idea before I forget, and I'm outside my personal experience with this one. Others will need to chime in.

I've focused this whole time on the valve, reading past the original post that you have this in a Micromag. I know very little about Micromags, but didn't some have an improper distance from where the bolt springs seats to the rear frame/field strip screw? If this distance is too short, will it compress the bolt spring excessively, causing sub-par velocities throughout the entire reg adjustment?

If your buddy's rig is fully functional and set to a desired velocity, just switch valves (including bolt and spring). See if his valve cannot obtain a desired velocity in your Micromag body and if your valve can achieve a desired velocity in his body.


-Nathan

You know what, I think you hit the nail on the head. I got air today to do some testing. I took my classic mag with functioning classic valve. It was shooting 280fps in the classic body. I changed nothing and put it in the micromag body and it dropped all the way down to 180fps. I tried my rt valve again in the micromag body. Wouldn't go above 250 fps. Changed nothing but put it in the classic body. It then shot beautifully all the way up to 300fps. So the fact that the hole is bored 0.150" longer on the micromag must be causing this issue. This should be a very simple fix now. I am off to turn a new steel bushing for the micromag that is just a little thicker to take up the extra space. I will report back with how a new bushing works.

[sniper42]

Interesting, I hadn't thought of that. I checked the micromag as well as my classic mag. The micromag body is actually .150" longer than the classic mag. And that is with the steel bushing in the micro. Would the body hole being too long cause this sort of problem? I have yet to get air, been busy with work and machining some parts for a buddy's gun. When I do get air I will put the rt valve in my classic body and put the perfectly functioning classic valve in the micro and see if anything changes.

[nak81783]

Just another idea before I forget, and I'm outside my personal experience with this one. Others will need to chime in.

I've focused this whole time on the valve, reading past the original post that you have this in a Micromag. I know very little about Micromags, but didn't some have an improper distance from where the bolt springs seats to the rear frame/field strip screw? If this distance is too short, will it compress the bolt spring excessively, causing sub-par velocities throughout the entire reg adjustment?

If your buddy's rig is fully functional and set to a desired velocity, just switch valves (including bolt and spring). See if his valve cannot obtain a desired velocity in your Micromag body and if your valve can achieve a desired velocity in his body.


-Nathan