Just got my first brass marker and I could use advice

[Impactfour]

Well I'll be sure to keep these things in mind when I can get in front of a Chrono.

So far the suggestions are:
Piercing 12g too little (could be this based off small holes in spent 12gs I pulled out of my dump pouch)
Main spring too weak/valve spring too strong
Valve stem is too long


For now I've got two valve pins and two valve springs to experiment with. I figure I'll bring the springs, pins, calipers and sand paper to the field.

First 'fix' will be messing around with the pins to see if one pierces better and makes a difference.

Second 'fix' will be mixing the valve springs up, and potentially main spring if I can find a replacement.

Last ditch effort will be shortening on of the valve pins as described by spider, as it's the most permanent.

I'll let you all know how I fair. If none of these solutions work out I'll come back to the idea of opening up the valve for better airflow.

Edit: I'm also looking into chronographs, so I can fine tune the pgp (and hopefully that spyder project) if anyone has any suggestions I'd love to hear them.

[Spider!]

One thing that is hard to grasp is that some valve stems are about a tenth of an inch longer than they need to be. That robs the hammer and main spring of usable energy. You only need between .25 and .31 of and inch of valve opening, .375 or more is not useful on a short barreled co2 marker.

I grind them down about .090". That sounds small, but remember what kind of adjustments you use on the rva.

[Spider!]

There should be enough space in the valve chamber to render any pierce size adequate. Iirc, BretG had often said smaller is better, which I firmly believe on normal configurations.

[JeeperCreeper]

Yeah I definitely feel like it should hit at least 260. Might be a weak hammer spring. I've also heard somewhere some of those PPS valves were just barely too short to properly pierce the 12g, maybe someone can verify

[Impactfour]

I'm gonna peek through my spring collection tomorrow and see if I have anything that matches the valve or hammer spring. While I'm at it I'll run a few 12 grams through it and see how well they are pierced.

[BrickHaus]

Sounds like your brass needs a bit more work to get up to speed. This is odd as typically these baddies shoot fine on co2. People usually report low 200s when switching to hpa. I think you just need a new hammer spring from the sounds of it. You are at the point of the hammer loading up against the RVA so you can't get enough tension to open the valve enough.

You can find a combination of stiffer drive spring, or lighter valve spring to allow the valve to open more and or increase dwell time. The issue is you find a super stiff drive spring and your pump stroke is harder.

Your valve spring being too soft causes you to run into potential leaking issues.

8s start by finding an equivelantish spring to replace the hammer one, and start there.

You may have to open the air transfer ports up slightly on your valve as well. But I'd start with the spring.

Another thought is you arent piercing the co2 enough. The pierce pin lengths are all over the place. If you are just pin holing your 12ie you may be running on starved air.

[Impactfour]

So the adjustment screw is 1/2" the ball bearing looks like it's 1/4" or 6mm. Either way, when screwed in just short of flush with the cap it hits about 240 fps, any further and it barely functions.

[Impactfour]

There's already a ball bearing in the RVA, maybe some more shimming will do it. I'll have to measure the adjustment screw when I get home, but it's currently nearly all the way dialed in if I give it another half turn or so the marker barely makes a sound and paint come out quite slow.

[Carp]

Have you tried putting a ball bearing/shim behind the main spring yet? I have had success raising fps with just shimming, between the RVA and the spring.
Edit.. shimming may not work with a stock rear plug converted RVA. How long is the adjustment screw?

[Impactfour]

So I brought it to the field a few times and haven't found a way to get it shooting above 240 fps or so. Screwing the RVA in beyond this point would cause a complete fps drop off.

Is this normal and should be expected, or will replacing the main or valve spring result in a higher fps?

[Impactfour]

I sure hope so. The first time I brought it out the valve was gunked up with brasso (oversight on my end), so tomorrow will be the real test to see if it performs as well as it looks. If I fall in love I think I'll get a brass k frame.

[Carp]

That there, is a quite capable looking..... Click, Clack, Blooper. 👍

[Impactfour]

JeeperCreeper generously hooked me up with a new pump handle bored out for a bb bearing, a front sight, and an entirely new trigger frame with a safety. With the PPS parts I got, this is how the marker currently sits.

I was able to cut down a mechanical pencil spring, and used a .177 bb as a bearing in the new pump, it works brilliantly. I'll drill out the plastic pump I started with to match in case someone else needs a pump with a bearing.

I plan to drill an allen key hole in the new frame, but
I'm debating painting this one matte black rather than gloss, any thoughts would be appreciated. On a related note, does anyone know how to remove the safety from the grip frame?

I also did a bit of research and found that drilling brass is a little more complex than I expected from my experience with aluminum and stainless. Apparently entirely different bits are required, so I was thinking I should get some practice first. Anyone have a good source for a comparable tube of brass to practice drilling on?

[JeeperCreeper]

It's amazing how simple they are. Just a good cleaning and some oil goes a long way with these

[Impactfour]

Well I just put it back together and put a couple of rounds through it, seems like just getting the gunk off it got it shooting much better. Hopefully this upcoming week I can clean up a few more pieces, and drill out the feed tube. Almost there!