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Flashpup .25, 810fps on 150 bar reg. Port?

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Droppingpins

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Jan 31, 2020
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hey guys. I put a huma reg on my flashpup. I set to 145 bar and got to about 810 fps on 145 bar, going up to 150 bar gained me nothing. That is on jsb 25.39. Is this the limit on the transfer port? The port on the flashpup has been reported to be .116(i havent measured it, but airgunners edge reported that in his video)

I have taken everything apart, checked o rings, all look good. Gun holds air pressure overnight. Replaced the pellet probe o ring just in case. Pushed a pellet through and it looks ok. I inspected all o rings from the valve to the barrel as closely as i possibly could, im pretty damn confident theyre great. I used a borescope to align the barrel port to transfer port(it was way off from the .factory, its not perfect but pretty damn close). Pushed a pellet through a clean barrel and it was very smooth. I am adjusting hammer spring tension with the 4mm allen key. When i tune it in to 810 on 150 bar i get only about 15 shots. This might be way past the knee of the curve but i think it might be valve dwell, possibly need to shim the valve spring(curious to see what you guys think on that)

My goal is 830-850fps with jsb kings. Any thoughts? Thanks guys, this is only my second pcp tuning, but i absolutely love the tedius work involved. So satisfying.
 
If you want power you are better off removing the regulator and tuning it without a regulator if you want the same or more shots at a higher power level.

You have a MAX 2900psi fill rating.The reservoir is only 165cc and rated at a maximum of 40fpe per factory unregulated specs that's just under 850fps with the 25.39gr JSB Kings. Adding a regulator already puts a cap and lessens that max power.

I would just tune it for maximum of 800fps shooting 25.39gr JSB Kings lower the reg pressure to make that regulator work for you and get a couple more shots as how it's intended. That's 800fps for 36pe vs your wanting 850fps for 40fpe that's wasting a lot of air and shots for only 4fpe. Even 777fps is 34fpe and only 6fpe difference and get there's a good number of extra shots. If it were me I would be content with 750fps for 31-32fpe that ought to have great killing effect on medium sized game.
 
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hey guys. I put a huma reg on my flashpup. I set to 145 bar and got to about 810 fps on 145 bar, going up to 150 bar gained me nothing. That is on jsb 25.39. Is this the limit on the transfer port? The port on the flashpup has been reported to be .116(i havent measured it, but airgunners edge reported that in his video)

I have taken everything apart, checked o rings, all look good. Gun holds air pressure overnight. Replaced the pellet probe o ring just in case. Pushed a pellet through and it looks ok. I inspected all o rings from the valve to the barrel as closely as i possibly could, im pretty damn confident theyre great. I used a borescope to align the barrel port to transfer port(it was way off from the .factory, its not perfect but pretty damn close). Pushed a pellet through a clean barrel and it was very smooth. I am adjusting hammer spring tension with the 4mm allen key. When i tune it in to 810 on 150 bar i get only about 15 shots. This might be way past the knee of the curve but i think it might be valve dwell, possibly need to shim the valve spring(curious to see what you guys think on that)

My goal is 830-850fps with jsb kings. Any thoughts? Thanks guys, this is only my second pcp tuning, but i absolutely love the tedius work involved. So satisfying.
Click to expand...

You don’t say which Flashpup you have, Wood or synthetic. I know there are a few differences. The Flashpup I have is wood .25 cal and was purchased new in December of 2019. I have spent quite a bit of time working on mine both regulated (Huma) and unregulated and have kept very good notes of everything done so the following information may be of value to you. BTW, I know all the spec data for that rifle says the barrel is 19.4” but mine measures 17 5/8” so take that for what it is worth.



USE ANY AND ALL OF THIS DATA AT YOUR OWN RISK. THIS DATA IS FROM A SAMPLE OF ONE GUN, YOUR RESULTS MAY VARY!





Miscellaneous data for the gun as it was delivered from the factory;

Hammer spring preload = 1.5 turns CCW from full CW (CW is min preload)

Valve exhaust port = .160”

Transfer port = Starts at .165” and funnels down to .145” …odd

Barrel port = .185”

Air tube ID is 26.5 MM



Initial velocity data with dead stock factory tune.

H&N Field Target Trophy 20.06 gr= 880

JSB Exact King 25.39 = 810

H&N Baracuda Extreme Hunter 28.24 gr = 764

H&N Grizzly 31.0 gr = 724

H&N Baracuda 31.02 gr = 780

JSB Exact King Heavy MK1 33.95 gr = 745

JSB Exact King Heavy MK2 33.95 gr = 741





Here are the mods I have done to boost the power;

Cleaned all the internals of the action and polished the hammer. Opened up the valve exhaust port and transfer port in receiver to .180” and chamfer and polish. Made a new valve seat out of ‘PEEK’ plastic with a bore size of .205”. Installed a very light valve spring on poppet.



With these mods done I was able to get the JSB 33.95’s running at an average of 811 FPS (50 ish ftlb) for 20 good shots unregulated but I was not happy with the Extreme Spread (41 FPS). At this tune the 25.4’s were running 920 FPS (48 ish ftlb).



I put a Huma regulator in the gun and started playing around with pressures. It appears to me that the plenum is much too small on the Huma reg to expect high velocities at low reg pressures. I played around from 140 bar up to 165 bar and ended up using 165 bar. Here is data doing hammer spring adjust at 165 bar reg pressure;

Bump reg pressure up to 165 bar (approx. 2400 PSI)

With JSB 33.95 pellets;

HS 4 turns CCW = 710 FPS

HS 4.5 turns CCW = 740 FPS

HS 5 turns CCW = 772 FPS

HS 5.5 turns CCW = 797 FPS

HS 6 turns CCW = 808 FPS

HS 6.5 turns CCW = 815 FPS

HS 7 turns CCW = 815 FPS



I settled on 4.5 turns CCW on the HS and here are shot strings with both 33.95 and 25.4 pellets. My gun shoots both pellets VERY well but the 25.4’s are flatter out to 75 yds so that is what I am using most. Please note that I am filling the gun to 3100 PSI instead of 2900 and am completely comfortable with doing that. 7% overfill… pressure gauges on these guns aren’t that accurate…















There is a guy over on the GTA forum that has done a TON of work / mods on Flashpups and most of the work I did on mine was influenced by following in his footsteps. His user name on GTA is "Rallyshark", you should go look him up. Good luck on your quest! Chip
 
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Thanks. I have the wood stovk but from little I understand I have the updated one because the hammer spring moves freely when you shake it it rattles.



Good to know, I was worried I should get more out if it than I was getting with the stock port.

I dont hunt, I mainly want the power because u feel it's the sweet spot for exact kings at longer ranges and gives me a chance to play with the wind tuning.
 
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If you are keeping the Huma in it, I would drill the TP to .125. I would also check the Huma manual for that reg. I know my Huma in my BSA/Urban said to drill the TP to .160 in the directions.
Click to expand...

So, interesting enough, the reg fits the flashpup and flash, being supposedly the same gun. However, for some reason the flash on airgunners edge video had a .150 port, while the flashpup had a .116 port. I dont have a full set of drill bits to try to size it myself, so I'm just going off his info. I did out some math, going from .116 to .150 port will increase the area of the hole by 75%(going to. 160 gives it damn near 100% increase in area).
 
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