Piranha HPA vs. co2 & recock questions

[glaman5266]

Hello. I've acquired a couple Piranhas & after rebuilding them I stumbled across a couple issues.

GTI ('03 maybe?): It airs up with no leaks & throws paint. However, if I rip a few quick rounds it quick-farts & decocks. In my testing I didn't have a bottomline, so I just screwed the HPA bottle straight into the VASA. Is the decocking simply because of lack of volume? I plan on putting a gas-thru on it anyway, so maybe the problem will fix itself?

'04 SRT: After a full rebuild, this one farts & decocks on the first trigger pull. As opposed to the GTI, this one has a bottomline. I've swapped out for lighter hammer springs and I can't get that behavior to change. Even with my lightest spring the bolt feels awful hard to pull back. This was also tested with HPA. Maybe start clipping the hammer spring?

As I've stated, I tested both with HPA. I haven't had a Piranha since before I bought my first HPA tank, which was maybe in 2007. When I ran co2 on Piranhas back then I had no issues. Do Piranhas simply function better on co2?

Thanks for reading.

[iamthelazerviking]

Tldr yes. For whatever reason Piranhas do better on CO2. Spyders can take an 800 psi+ HPA and be good to go.

[Toestr]

What is your tank output? I've had no issues with earlier Piranhas that have no gas through on ~800psi.

Typically if a blowback is sputtering you want to increase spring tension (although too heavy a spring can cause the same issue). Cocking it shouldn't be any harder than any other typical STBB.

[glaman5266]

Not sure what the tank output is. It has a plain, base model Ninja reg.

The SRT does feel like it cocks harder than others. I’m planning on tearing into it again to maybe see what’s up.

[Chappy]

Are you shooting paint? Silly question but the blowback from paint vs dry fire can make a difference with hpa on blowbacks in my experience.

[glaman5266]

Yeah, I’ve heard this as well, though I’ve never seen it myself. I ran paint through the GTI. It would shoot, but if I fired a burst it would decock. I didn’t try paint in the SRT.

[Trbo323]

Yeah shove a swab down the barrel and dry fire. Fish like back pressure this is why they typically work better when shooting paint over dry firing

Tldr yes. For whatever reason Piranhas do better on CO2. Spyders can take an 800 psi+ HPA and be good to go.

From what I've understood, it's an energy density thing. As co2 flows into the marker there are still tiny amounts of liquid vapor floating in the gas. That little bit that still needs to expand into a gas makes the difference.

It's also that fish have larger hammers than spyders. They still run an 015 o ring on the tip but after that the Piranha hammer has more mass and therefore needs more energy to recock.

The flip side is this is why piranhas are typically easier to get up to velocity

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