Larger plenum for Huma regulator??

[Rallyshark]

Well, 80 fpe is the hottest "hunting tune" I run on it(porker tune), but I have gotten it as high as 85 fpe at full tilt.  I consider a minimum power tune to be at least one magazine(12 shots).  That power tune is with it shooting 35.2 grain slugs a little over 1000 fps.  And yes, it is tweaked to the last micrometer, haha.  It also has a BT65 cylinder and a 700mm slug liner made into a barrel.  There ain't a whole lot left of the "original" gun.  I don't think there is any more power possible out of it at this point. 

I'd recommend getting a chrony first and foremost!  Without that, everything you do is just shooting in the dark.  You need to run a string with it like it is, then pull the reg and see what it will do.  With the reg setting you think you're at, I don't see how you're getting that many shots, unless it is tuned way below the knee?  If you're getting that many shots, I'm guessing the velocity would have to be pretty low.  Again, I'm shooting in the dark here too, since we don't know what speed you're shooting.  Can you tell me all of the mods that have been done to it? 

[Cableaddict]

I'd recommend getting a chrony first and foremost!  Without that, everything you do is just shooting in the dark.  You need to run a string with it like it is, then pull the reg and see what it will do.  With the reg setting you think you're at, I don't see how you're getting that many shots, unless it is tuned way below the knee?  If you're getting that many shots, I'm guessing the velocity would have to be pretty low.  Again, I'm shooting in the dark here too, since we don't know what speed you're shooting.  Can you tell me all of the mods that have been done to it?

I'm sure of the regulator setting. 
Velocity with the Griffin 36gr cup based slugs was about 870 FPS, according to my notes.

I don't know how far this was drilled, or if it has any other mods like hammer spring, pellet probe tweaks, etc.  I didn't do any of the internal work.

I'm pretty sure I dialed-back the hammer spring 1 or 2 clicks from stock, but again I just can't remember. I never wrote it down. That of course is critical for maximizing power without wasting any air.

Well, it's all moot until I get the new HUMA tube, and a new chrony.   I still haven't settled on my main ammo, either, so I'll have to re-tune regardless.   I'm really liking those Griffins, but lorda'mighty they are are expensive.

The only other mods I've done is to shop off the front of the main picatinny rail, as it's useless and weighs a lot,  and (seriously) I ground down the back rail, after removing the cheek rest.   I dunno what Hatsan is thinking with that useless rail and thick rest. They make your cheek weld ridiculously high.   Really bad for short-range hunting.  (Bullpups are bad enough, to start with.)

-  Just grind the sucker off, then grind an angle into the top-side edge as well. Then glue on some really thin dense foam.
The difference is incredible.
------------

BTW,  I would LOVE to see a detailed list of everything you did to that .22.   Holy cow......   

##  I assume you needed the longer barrel in order to fit a larger air tube, yes? 
I'd love to go larger with mine as well, but even if I could find something pre-made, there's very little room for going to a wider diameter. 
A BT65 cylinder would never clear the shroud on a stock Flashpup. But assuming I found a barrel for cheap, do the cylinder and barrel mount to the Flashpup without modification?  If so, it's a very interesting idea. 

Cost aside, you end up with a 23" barrel on a 35.4" rifle, and a separate pressure gauge for the air tube and gun chamber.  Plus you could go bananas and get one of those non-choked LW barrels from Poland, and be the Lord of the Slugs.  (Well, in .22 cal anyway. Sadly, they don't have them in .25)   No shroud though, but I suppose you could just extend the Flashpup's shroud with some plastic tube or something....

Oh Lordy, I have to stop all this caziness now!       
 

[AlanMcD]

In my experience tuning Marauder's with regulators for higher power, whenever I increased the plenum size (which of course takes away from the high pressure reservoir space), I usually got more power AND more shots as a result.  It turns out that the increase in efficiency that results from the higher average shot pressure in the larger regulated space typically more than makes up for the reduced volume of high pressure unregulated air.

Of course if you truly are going for "max power" you will probably find that you can get more power by tuning without the regulator . . .

[Rallyshark]

In my experience tuning Marauder's with regulators for higher power, whenever I increased the plenum size (which of course takes away from the high pressure reservoir space), I usually got more power AND more shots as a result.  It turns out that the increase in efficiency that results from the higher average shot pressure in the larger regulated space typically more than makes up for the reduced volume of high pressure unregulated air.

Of course if you truly are going for "max power" you will probably find that you can get more power by tuning without the regulator . . .

You ain't wrong!  I always err on the side of a larger plenum when regulating a gun for those very reasons  

I'd recommend getting a chrony first and foremost!  Without that, everything you do is just shooting in the dark.  You need to run a string with it like it is, then pull the reg and see what it will do.  With the reg setting you think you're at, I don't see how you're getting that many shots, unless it is tuned way below the knee?  If you're getting that many shots, I'm guessing the velocity would have to be pretty low.  Again, I'm shooting in the dark here too, since we don't know what speed you're shooting.  Can you tell me all of the mods that have been done to it?

I'm sure of the regulator setting. 
Velocity with the Griffin 36gr cup based slugs was about 870 FPS, according to my notes.

I don't know how far this was drilled, or if it has any other mods like hammer spring, pellet probe tweaks, etc.  I didn't do any of the internal work.

I'm pretty sure I dialed-back the hammer spring 1 or 2 clicks from stock, but again I just can't remember. I never wrote it down. That of course is critical for maximizing power without wasting any air.

Well, it's all moot until I get the new HUMA tube, and a new chrony.   I still haven't settled on my main ammo, either, so I'll have to re-tune regardless.   I'm really liking those Griffins, but lorda'mighty they are are expensive.

The only other mods I've done is to shop off the front of the main picatinny rail, as it's useless and weighs a lot,  and (seriously) I ground down the back rail, after removing the cheek rest.   I dunno what Hatsan is thinking with that useless rail and thick rest. They make your cheek weld ridiculously high.   Really bad for short-range hunting.  (Bullpups are bad enough, to start with.)

-  Just grind the sucker off, then grind an angle into the top-side edge as well. Then glue on some really thin dense foam.
The difference is incredible.
------------

BTW,  I would LOVE to see a detailed list of everything you did to that .22.   Holy cow......   

##  I assume you needed the longer barrel in order to fit a larger air tube, yes? 
I'd love to go larger with mine as well, but even if I could find something pre-made, there's very little room for going to a wider diameter. 
A BT65 cylinder would never clear the shroud on a stock Flashpup. But assuming I found a barrel for cheap, do the cylinder and barrel mount to the Flashpup without modification?  If so, it's a very interesting idea. 

Cost aside, you end up with a 23" barrel on a 35.4" rifle, and a separate pressure gauge for the air tube and gun chamber.  Plus you could go bananas and get one of those non-choked LW barrels from Poland, and be the Lord of the Slugs.  (Well, in .22 cal anyway. Sadly, they don't have them in .25)   No shroud though, but I suppose you could just extend the Flashpup's shroud with some plastic tube or something....

Oh Lordy, I have to stop all this caziness now!       
 

Fun fact, a Nova Star/Neutron Star barrel will fit the Flashpup   That would probably give you a long enough barrel to clear a BT cylinder.  Also, the BT cylinder will screw onto a Wood Flashpup valve, and is the same OD as the factory cylinder.  It will not fit a Synthitic Flashpup though.  I put a Wood Flashpup valve on my SFP so I could use a BT cylinder.  A LW barrel from Europe is not a guarantee for a good slug barrel, fyi.  That is why I made a barrel from an FX Slug A liner, because I knew the odds were good it would like slugs.  If you want less expensive slugs, order a sample pack for NSA to see if it likes any of theirs.  They are much less expensive.  That isn't a knock against Griffin, because he makes good stuff too, but NSA has the best prices out there.  I like Griffin slugs, because they will make you almost anything you ask for, but it will cost more.  They are my go to for heavy .177 slugs. 

Here's a couple of links to some of my posts on the Flashpups:

https://www.gatewaytoairguns.org/GTA/index.php?topic=164310.msg155833574#msg155833574

https://www.gatewaytoairguns.org/GTA/index.php?topic=166895.msg155869464#msg155869464

As you already mentioned, discussions on performance of your gun are kind of moot, until you can get a chrony back in your hands.  I'm guessing some of your info may be mixed up along the line, or your chrony was reading wrong?  I have seen many chronographs give some pretty crazy readings in odd lighting situations.  It would be darn near impossible to get 16-17 shots at 60 fpe on a regulated Flashpup of any caliber.  They have to be opened up pretty good to make 60 fpe unregulated.  It could possibly make that power with a reg setting of 180 bar, but you'd only be working with 20-25 bar of extra pressure in the cylinder.  The only way to get that many shots would be to massively over-fill the gun.  If you are over-filling, we don't want to know about that part, because this thread will get locked down faster than you can blink an eye.  The mods don't play about over-filling guns on here.  You know, safety and all   I'm not saying you're telling stories or anything like that.  I'm just saying that about the shot count, so you don't have unrealistic expectations is all.  You'd be lucky to get a 15 shot 60 fpe tune on a regulated 255cc BT cylinder, much less with a 165cc Flash cylinder. 

Cruise through those links I gave you, because there's some input from guys that tuned their .25 Flashpups in there too.  I'm sure some of that info will be useful   You are right, tuning these guns can be quite the rabbit hole though!  I look forward to seeing what you come up with either way! 

 

[Cableaddict]

Fun fact, a Nova Star/Neutron Star barrel will fit the Flashpup   That would probably give you a long enough barrel to clear a BT cylinder.  Also, the BT cylinder will screw onto a Wood Flashpup valve......

All this info is GREAT.  THANKS.

But thinking on it a lot,  I'm not sure it's worth the expense seeing as it would make my bullpup almost 36" long.
Someday I'd love to buy an RTI Prophet, or maybe an FX Maverick, but I doubt that will ever happen.
For now, living with slightly less velocity, and having to carry a buddy bottle seems like an acceptable trade-off.

Something like this:  (My actual goal)

https://www.dropbox.com/s/8prrw2gr8w5cuvd/Flashpup%20w%20bottle%20-%20variants%20-A%20%20.jpg?dl=0

[Rallyshark]

A user on here, darkcharisma has done exactly that.  I believe he posted about it in the last few pages of the "Sythetic Flashpup Adventure" thread I linked above.