Can I modify, or am I angering the Brass Gods ?

[Oddbawl]

I got my greasy mitts on a Piranha Rifle. Seems pretty much un-messed with as far as mods, just as I remember the last new one I manhandled in a shop.
My question is this: is it total blasphemy to mod it a bit? I'm thinking Wedjits and a 12gram cut out etc, but don't want to incur any wrath from The Brass Gods by mucking up a relatively untouched example.
Thoughts? IMG_63241.jpg IMG_63231.jpg IMG_63201.jpg IMG_20210902_195055.jpg

[Jordan]

Do it! Although a DF 12 gram gun will be an oddity.

Just don't pirate the stock, please... I have an extra pirate stock if you really want one.

[BrickHaus]

As long as you still take sould with it on the field, rock it.

Though, I suggest opening up the valve, and body ports, then getting a 22ci tank for those ring mounts and running a 50 round hopper. I have a very similar rifle, and love using it open class like that.

[Brokeass_baller]

I have a 22ci/3000psi tank of you want one. Shameless plug.

[Oddbawl]

I personally don't really get the Pirate thing, to each his own, I prefer the M79 thing...
If I were going to do something similar, I'd make one rather than hack a perfectly good stock.
As far as a drop out, I like the versatility,. I made a dummy 12gram with perpendicular npt threads to do a vertical set up on various guns.

[Jordan]

Good... I get why it's done, just hate to see it.

[Oddbawl]

Oh my God I am about to throw this thing in the lake.
Total clean up, popped in wedjits, holds air fine. It lobs paint a bit slower than I can throw it only a lot louder.
I pulled the valve, opened up the ports, put shims behind the hammer spring, not a damn thing changes velocity. Tried HPA and co2
What am I missing here?

[ATBen]

Output pressure on your tank is too low?

[XEMON]

Transfer ports clogged/too small?

PS: shoot me a PM before throwing it ... I would re-home it in my greabag 😉

[Oddbawl]

I tried co2 as well. Nada.
I'm taking the same approach as with carburetors etc.
The fricken thing must've worked at some point in time, so what has changed?

[Mr. Hick]

the widgets only keep the small paint from rolling out. it still takes more air than a 12ie is possible to launch a .677 ball at field speed down a .695 bore.

[Oddbawl]

Aha!
That's the perspective I needed. I've never run into this before with PGPs and PMI-1s, but none have a barrel this long. That's what's been driving me nuts. It's loud, seems like it's doing what it should, that must be monster blow by.
I'll open up the transfer port next.

[BrickHaus]

I bring my kp to the field, and depending on how the paint sizes it may or may not get used. I have it dialed in at 290 ish on a nicely matched paint. I had some oblong and tiny field grade paint 2 weekends ago that I couldnt even get above 250 on any if my brass with that paint. Ended up rurning that case off that day with a mech just to be rid of it. But man, when its hot out, and paint is nice an fat. Sheridans are tack drivers.

[Meleager7]

Build a siphon tank and run it on sweet liquid! Actually, can the old Sheridan guns handle liquid co2? We should ask that first!

[Jordan]

The focus is going to be trying to balance valve dwell with flow... have you opened up the air transfer port between the tube? Are the ports in the valve lined up? How's the springing? How's the bolt opening - tiny?

I know people like to blame barrel size... but my Hurricane has no issues shooting .680 paint out of it's. 690 barrel at 280FPS with 800psi input, and I've built 12gram powered Snipers that used a stock bull barrel with nail polish wedgits that again shot 280FPS with 600psi input - and got close to 40 shots per 12gram.

Like carburetors, it's a matter of tuning using a bunch of adjustments.

[Oddbawl]

Agreed,
I've got big bore stuff that still lobs fine.
But again, the thing looks pretty factory, and must have been useable at some point in time, so I was looking at tuning before alterations.
Now, the factor that has changed is paint size, so I do suspect it's transfer port is too wee now as it needs to compensate.
Your Hurricane likely flows a helluva lot more than the wee orifices on this thing.

How are yooze guys doing it? I was thinking of drilling through the bottom, the either tapping it if there's enough meat for a set screw like the Snipers or sealing it up with more lead.

[Jordan]

Drilled it out - measured and drilled from the bottom.

I used a 7/32 drill bit and tapped for a 1/4"-20 setscrew - there's enough meat there for 3-4 complete threads, more than enough.

I also drilled out the bottom port of my bolt and angled it slightly, but haven't modified my main port much yet, I'm leaving that for tuning once it's all together.

I also modded my valve a bit - I'm running a custom Sheridan valve from JG Airguns that already has slightly bigger porting, I did a little massaging on the input side of the valve and blocked off two ports with setscrews to help force the air through the top port. I'm going to run a PPS Dynavalve which has a necked down valvestem similar to a Rat valve cupseal or Tornado setup.

I haven't settled on a valve spring yet, but I've got a bag full of misc that I can pick from.... PPS used a cut yellow Cocker valve spring in one of my Typhoons, so I'm sure it doesn't matter that much.

[Oddbawl]

I like the cut of your jib. I'm really not in the mood to separate the tubes!
I opened up the ports onthe valve, and have turned down stems in the past to mimic the Turbo Valve stems from back in the day.
Away I go!

[Gazoo]

Leave hammer spring stock and get a lighter valve spring. Will correct most of your issues

[anson]

Any update on this?
I am having the same issues with a P68