Diana Skyhawk/ P15 what is the maximum FPE that you can reach in cal 22

The oem plenum is a little small for going above 30fpe with decent shot count. You can get to the low 40's but your shot count will be in the 20-30shot range.

You can do this with the OEM reg, but the huma is more consistent.

I've reas where the m10 reg can be used but the valve connector/OEM plenum requires modification. I don't believe this plenum is as large as the one vash545 makes.

Add vash545's 15cc plenum extension and low 40fpe tunes in the 30-40 shot count are attainable. I have measured the OEM plenum with water, it is approximately 10cc. Vash545 extension is another 15cc, giving a total of 25cc.

25cc is a big difference. My opinion on .25 is if I'm below 44ftlbs, then I'm going into a loopy trajectory. My old AZ Rapid was set at 44.69ftlbs 25.43 Kings at 880fps, so I don't wish to do with less.

The Skyhawk is a vERY attractive rig though I've yet to own a bull pup air gun and I'm considering one if I found off hand shooting to be easier, more stable.

I'm very interested in this rifle but I must close this out. Good luck

With that 10cc extra plenum the P15 from 27 goes 33 ft/lb without touching nothing

reg was at 120 bar, JSB 15.89

i suppose with the reg at 140 bar and HST you can get 40+ ft/lb

Where can I order the Vash545 extension? Google hasn't been much use.

Huma sells a regulator for P15 with extra 12cc plenum

zoom near the breach, this is the extension from my gunsmith, 70fpe in .22 with reg set to 135 bars, do not read the fx gauge she's wrong

I have Lee545 plenum, Huma at 145 and a 20 inch LWPOLY Chocked barrel, with the 22 cal JSB 25.4 I am 895-900 FPS/45 FPE. The 34 grain pellets pick up a bit more fpe, but don’t fit in the magazine, are not as accurate as the 25.4. This is all with preloaded maxed.



Roachcreek

I have too the Lee545 plénum extension and it's a very good pcs. Perfectly machined. 

I have this pcs pcs 2 years now and no problem

Huma power plenum, custom valve poppet, valve needle reduced 22.7 LW Barrel, custom hammer spring, in .22 i get 44 ft lbs no problem, reg at 140 bar, with a little tuning I could get 50ft lbs, but am happy with lower setting, most accurate around 34 ft lbs with 18.13 JSB

Great thing is although you have all that air on tap, you don’t have to use it. I can turn mine down by backing off the preload to flush and shoot 14.’s at 900 FPS. It does not quite have the shot to shot consistency doing this however still very accurate.

Lee does great work.



Roachcreek

My thought was to simply increase the plenum volume, drill out the transfer port from 5mm to 5.5mm, and tune the hammer spring to get better accuracy at 100 yards in the wind using NSA slugs for hunting. If this isn't going to end up being as accurate as the stock config with JSB 18's, I may just leave it stock.

Has anyone tried the NSA 17.5 grain dish base slugs in a stock p15 or Skyhawk?

My goal is to keep the accuracy/improve it while using a slug that will buck the wind better than diabolos and transfer energy with a POP when it hits. Sure, heavier is better but shot count is kinda nice to have as well.

Also, has anyone tried using the titanium tube on the Huben K1 to raise the fill pressure for more shots?

25cc is a big difference. My opinion on .25 is if I'm below 44ftlbs, then I'm going into a loopy trajectory. My old AZ Rapid was set at 44.69ftlbs 25.43 Kings at 880fps, so I don't wish to do with less.

The Skyhawk is a vERY attractive rig though I've yet to own a bull pup air gun and I'm considering one if I found off hand shooting to be easier, more stable.

I'm very interested in this rifle but I must close this out. Good luck

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It obviously depends on what pellets you want to throw out of it. There are lighter weight pellets than Kings that could get velocities necessary for "non-loopy" trajectory. I would agree, however, that the Diana/P15 is limiting for the .25, because of the smaller plenum. Better suited to .177 or .22.

How much does the plenum extension cost? At some point it would make more sense to buy a Cricket or Veteran for a little more cash. With their larger plenums +50 fpe isn't a problem in .25. I like to be able to push a 26 gr. Predator Polymag at +920 fps. My Veteran is doing it at 950 fps (52 fpe.) 

With that 10cc extra plenum the P15 from 27 goes 33 ft/lb without touching nothing

reg was at 120 bar, JSB 15.89

i suppose with the reg at 140 bar and HST you can get 40+ ft/lb

Click to expand...

that cost me 30 €

Lee charges 73 bucks, you can contact him on this forum. Lee installed my plenum while doing other work on my Skyhawk.

I started shootings slugs in air rifles 8 years ago, I did video’s of hitting 12 oz cola cans at 500-550 and 615 yards. It seems folks want to shoot slugs, but most slugs end up gathering dust on their shelves because the buyers are not educated on what needs to be done before you order a mold or slugs. SLUG YOUR BARREL or shoot pellets, it is that simple. A slug needs to be .0005 to .001 over groove diameter and your twist rate needs to be comparable with your intended slug weight. It seldom is a plug and play alternative to diablo projectiles. Also chocked barrels are not the best option for slugs, some make it work, but it is not ideal. Google Roachcreek 615 yard Haley airgun shot on 12 oz cola can, it is grainy and fuzzy, but you can see it is possible. It was also done with a 4.5x14 vx3 Leupold scope and 80 grain spritzers from a mold designed in the 1930’s for the 257 Roberts.

Roachcreek

My thought was to simply increase the plenum volume, drill out the transfer port from 5mm to 5.5mm

Click to expand...

Don't drill through... drill 3/4 of the way and then elongate the last bit forward, putting a little radius on it for better airflow without feeding problems. Never make the port wider where the pellet slides across it. The following picture is exaggerated for clarity. You can't get that much radius on it but you get the idea.

My thought was to simply increase the plenum volume, drill out the transfer port from 5mm to 5.5mm

Click to expand...

Don't drill through... drill 3/4 of the way and then elongate the last bit forward, putting a little radius on it for better airflow without feeding problems. Never make the port wider where the pellet slides across it. The following picture is exaggerated for clarity. You can't get that much radius on it but you get the idea.

Click to expand...

You have to be careful with that radius. You want to be sure the transfer port does not extend past the pellet skirt. I believe when I checked the Gauntlet's port there is no room to extend the port forward without compromising the pellet skirt seal.

Αnd how you can drill the TP like that at the P15 inside the block ?

Αnd how you can drill the TP like that at the P15 inside the block ?

Click to expand...

I haven't worked on this exact model but you normally get it with a rotary tool and a carbide burr.

You have to be careful with that radius. You want to be sure the transfer port does not extend past the pellet skirt. I believe when I checked the Gauntlet's port there is no room to extend the port forward without compromising the pellet skirt seal.

Click to expand...

I agree. If you chamber a pellet before disassembly you'll be able to see how far you can go while porting.