Traders Airsoft Forums

I’m slowly customizing my TM 5.1 Hi-capas, and would like some feelings about the best type of piston head available, as well as some input about floating valves. Since Traders seems to be the hands-down best place for GBB build-up advice, I’m love some input from the pistolero crowd here, if I may.

Some background: the pistols are TM 5.1 Hi-capas with stock plastic slides. They are my skirmishing pieces, for use in a CQB environment with 335fps max with .02g bbs. I’m running them on green gas. Right now they have stock barrels with Nineball Purple VSR airseal buckings, but the barrels will be replaced with PDI 6.01s in the near future. I have replaced the loading nozzles with Shooters Design units. Down the road ($$) will be Davidson Custom slides.

What piston heads would you guys recommend to maximize velocity, consistency, and reliability and minimize gas wastage? So far as I know, my choices include:

Stock TM
PDI
Shooters Design
Airsoft Surgeon
AS lightweight BBU with integral piston head, with SD ring replacements
Dyna
King Arms (saw them recommended on a thread on ASB, which had some input from Trader's members. Where can I get these? Den Trinity and WGC don’t seem to have them)
Action

Other stuff:
I’ve heard that the Dyna have a tendency to blow the O-ring off at higher pressures? Yes? No? Maybe so?

Does anybody have the O-ring size of the ones that come with the SD piston head, so I could just buy a bag of $1 rings instead of a $20 piston just to get two rings?

What is the deal with floating valves with O-rings? I saw in the other thread that the King Arms set had them. Action’s offering on Den Trinity seems to have them too. Do they convey real-world advantages? Worth while to get, or should I just stick with the stock floating valves (what I’m using now in my SD nozzles, since of course the SD ones stick notoriously).

Sorry for the longish post. Any advice or experience you guys could throw my way on these questions, or pertinent ones I don’t know enough to ask, would be greatly appreciated!

Thanks in advance,
-Tuthmose

IMO for your max FPS @ 335, I suggest:
NineBall Dyna Piston - this is actually not a bad deal since it comes with a stiffer floating valve spring (and extra o-ring) which helps with velocity (slightly). I have not blown an o-ring on mine, just make sure it stays lubed. It maximizes gas efficiency and seals better with it's little vent holes.
I don't think the Action (o-ringed) floating valve is worth it, unless you are trying to get every last drop of FPS you can.
There are only 2 other floating valve springs available: Proud or Action. The Action feels like stock, the Proud is nice, but the NineBall is stiffest.

As far as cost, accuracy and FPS are concerned, you'd be better off with the NineBall 6.03 inner barrel.
Damn the inner barrel discussion to spawn yet again. Though, there are now newer barrels to consider: Creation 6.03, PDI Palsonite 6.01, MabBull 6.03.

I won't get into the inner barrel thing other than to say that my preference is for PDI 6.01's and I think that you have made a good choice.

As far as pistons go, I run 9Ball dyna's in my low power guns and SD's in my powered up build. Right now that means I have Dyna's in my P226 and 1911 and a SD in my 400+ FPS Limcat.

As I recall there was a thread about the o-ring blowing issue on arnie's a while ago. I think that Brian was having issues with his Limcat when he was running it on Red (or something like that). I think that a Dyna would be a great fit with your setup though.

Thank you, gentlemen. That's exactly the input I needed.

Does the o-ring on the Dyna head work optimally, or should it be swapped out for a bigger/smaller/thicker/thinner one? Does anybody have measurements of the SD and Dyna rings for comparison?

-Tuthmose

The o-ring is fine, don't worry about it. I can go measure them if you really want.

That's the big plus with the ported piston head, it doesn't have to have a prefect size o-ring (since the ports push it out for a better seal).

Thanks again guys (sorry for the late reply!). Don't worry about measuring the o-ring, the4thpower3 - I was just curious as to the size difference, is all.

Again thanks for the advice,
-Tuthmose