PMI Trracer velocity

[Refoogee]

Hey all. I have a PMI Trracer that I can't get up past 260fps reliably. It's got a .685 SSC barrel adapter on it, an old 14 inch cocker barrel, phantom spring kit (red spring hammer, green spring valve), brand new powertube, cupseal, and all new O-rings, etc. It's been ran off of an HPA tank (an old Valken 26ci tank, and a brand new Ninja 13ci tank), both shimmed to 850psi output. The velocity averages out in the mid 250's, maxed out once or twice at 270, and sometimes dipped into the upper 240's. I've tried a longer hammer spring, and I've tried shimming the hammer spring, and those options both lower the max velocity.

I've been frequently running into really similar issues with all my older markers, older 98's, older STBB pistols, come to think of it. No idea what else is left to do lol. Any ideas?

[coyote]

My first thought is always a tighter bore on the barrel.

[Morgenstern]

Yeah, do you have some especially small paint locally if it’s even shooting slow in 98s? I know older Trracers always shot a little slow and the large bore long barrel won’t help that much.

[Refoogee]

It's GI Sportz of some kind. Didn't think about the fact it might be really small bore paint. Is .685 really that big these days? The barrel is certainly longer than I wanted it to be with the adapter. I might cut it down since it's a cheap garage sale barrel anyway.

[Warmongrel]

The GI Sports paint that I have used is 4 and 5 star and it bores typically small around .675 - .680. I would definitely try a smaller bored barrel.

[scottieb]

If it's an issue with small paint, and it sounds it is, you'll want a barrel with a smaller bore. Trracer barrels are too thin to Freak bore, however you can get the body rethreaded to Cocker threads. You'll open up new opportunities for barrels that way.

[Drachen]

Do you have any sources on rethreading the bodies? I would love to run my cocker barrels in mine.

[scottieb]

Here on MCB you can try Kit, or Doc.

BMC Fabrication should be able to do it as well.

[Brokeass_baller]

Super Stanchy Customs makes an Autococker-to-Trracer barrel adapter, but you'll need to bore out your Trracer pump handle from 7/8" to 1" in order to use it. People with 3D printers could probably print an entirely new pump handle for you. That might be the cheapest option.

[Jonnydread]

With an 850 PSI output you should have no trouble getting up to speed, even with a stock barrel. I wonder if your springs are worn out, but like the others said try a tighter bore first. I use a .679-.681 on nearly all my guns these days.

[Refoogee]

grabbed an ssc adapter in .685 that's about an inch long, would I be able to just thread on a smaller bore cocker barrel to that, or would I need to get a whole new setup do you think? The springs have been replaced by new Phantom springs.

[Warmongrel]

you don't want to use the 685 adapter on a barrel that's smailler in bore than the adapter as that will cause paint to break. I would see if you can find a smaller size adapter.

[uglyduckling]

Polish the powertube and hammer, use a shorter barrel

[Psycho91]

Have you tried a stock spring setup, like just basic silver phantom springs

[Refoogee]

Have you tried a stock spring setup, like just basic silver phantom springs

Yes. Currently working on getting some smaller bore barrels to try out.

[Brokeass_baller]

Problem might just be the valve volume. These old guns were designed for CO2, which needs less volume than compressed air because of the liquid and vapor. I had an SL68-II that refused to shoot above 260 on HPA, but hit 300 on a 12g. My Hammer is similar. It gets about 270 on hpa.

[Psycho91]

Yeah I love these old guns they are probably my favorite marker TBH, I'm glad I stumbled on this cause I'm fixing to start playing again and ima be running mine on hpa

[XEMON]

If you have access to a lathe, you can always enlarge the valve volume and enlarge the asa-valve transfer port.

[Brokeass_baller]

^^yeah, there are mods that can be done. Like trimming back the surface that the cup seal presses against, enlargening air ports, etc. It can be done.

[XEMON]

Enlarging the transfer post can also be done with a hand drill ... The position is already there, just step it up a bit.
Careful with trimming the cup seal, it can cause timing issues.
I know people have done it successfully, but when I tried it it wasn't as consistent as I was hoping to get. On the other hand, I've had great results with enlarging transfer ports and coring out the valve on Nelson based system design to run on CO2 ...

[zinger565]

This might be a silly thought, but would one of the reg extenders add sufficient volume? Couldn't hurt, right? Would be cheaper to mod than taking a lathe to the valve.

[Brokeass_baller]

I have the HK one and do not recommend it. It chokes the airflow and I get shootdown. I think it doesn't depress the valve pin far enough.