Tuning the Diana outlaw 25.

[Dwight]

Ok so I got a huma reg turned it up to 145 then turned the hammer spring all the way in till it wouldn’t cock then gave a quarter turn back out (it cocks fine)but at best for a 25.39 grain exact 655fps this thing is supposed to shoot them at 702 F PS what am I doing wrong? I would love to shoot these FX hybrids but yeah that’s not going to happen not at 655fps help please

 

[vmaxpro]

Im not familiar with that gun but sounds like you lost plenum volume. Also, back out your hammer spring a few turns and bring it in quarter turns at a time over a chrono and find your high then slightly back it off from there. 

 

[Dwight]

Ok.thank you, I will try that way in the morning. 

 

[vmaxpro]

Are these guns regulated from the factory?

 

[biohazardman]

Port size is important too. You may need to port out the valve, transfer port and/or barrel to match to get higher velocities. If memory serves best size is like 75% of the projectile diameter. If you get it too big you pellets will be damaged and accuracy suffers.

 

[Dwight]

Yes they come regulated I switched to huma Regulator but I don’t know how many shots it takes to break in

 

[prfssrlee]

I am using the oem reg and have it shooting 25.39gr JSBs at 850 fps. Gives me just under 41 ft-lbs. I don't remember how many shots I get, but i think its somewhere between 3 and 4 mags. The oem reg is good, but "twitchy" to adjust. By that I mean that very slight adjustments make big changes (like 1/8th turn). 41 ft-lbs was everything I could squeeze out of it with only adjusting the reg and the hammer spring tension. I think more than that might require drilling the xfr port.

 

[Parrotculler]

Breaking in should not be the issue. Yeah, drill out the transfer port to 5 mm, 80% of the caliber. It's easy because contrary to many other guns the barrel itself does not require dremel work.

This gun already has a good plenum volume because of the extension piece between the cylinder and the breech. That enables higher power with a relatively lower regulator set point.

After opening up the ports to 5mm, you can tune the reg and the hammer spring tension (HST). Start with a 130 bar regulator set point and shim the short stiff hammer spring with 4 or 5 pvc or metal washers. Chrony your shots, starting with a low hammer spring preload (HST adjuster turned out) then gradually increasing it. If your power plateaus at the initial 130 set point before you reach coil bind you can increase the regulator set point with 5 bar increments for more power. At each increased set point further increase the HST with the hammer spring adjuster.

You could also try a lower valve spring preload if all this does not give satisfactory power. However this valve spring is special/tapered/difficult to replace ! If you want to cut it, do not take off more than a mm or two! You will start wasting air and lose shot count (+ accuracy, potentially) if the spring becomes too weak -- and shimming it back again has its limits!

Please keep us posted. I have a .22 cal and like it; might go for a .25 if your results are good.

 

[smythsg]

I have the MrodAir Dominator (same as the Diana Outlaw) in .25 cal. It is also outfitted with a Huma regulator (not sure what I have it set at, been a while since I had it apart) and it shoots very consistant at between 48-50 ft lbs depending on the pellet/slug. Right now I am usually shooting the 29.5 gn NSA slug at a little over 48 ft lbs, but Baracudas shoot at 50 ft lbs. The one thing that I have done, that I did not see in your post, is shim the hammer spring with three washers. You might want to experiment with that approach to see if it helps.

 

[MBG]

From memory Internal breech porting is 5mm, check valve port size, it should be 5 mm, and you can drill out barrel Transfer Port to 80% of bore...Otherwise add a plenum , I have the extreme Airguns plenum on mine, so it does not take up space in airtube, reduce valve stem diameter only the last 40% towards valve poppet, reshape valve poppet only on the sides, not on the sealing surfaces...If you still need some speed you can add a longer barrel, however you will probably only be able to get this gun into the mid 800's...

 

[Parrotculler]

I have the MrodAir Dominator (same as the Diana Outlaw) in .25 cal. It is also outfitted with a Huma regulator (not sure what I have it set at, been a while since I had it apart) and it shoots very consistant at between 48-50 ft lbs depending on the pellet/slug. Right now I am usually shooting the 29.5 gn NSA slug at a little over 48 ft lbs, but Baracudas shoot at 50 ft lbs. The one thing that I have done, that I did not see in your post, is shim the hammer spring with three washers. You might want to experiment with that approach to see if it helps.

@Smythsg -- are you shooting the Baracuda Grizzly? What distance, and how good are your groups?

Shimming the HST spring by adding washers certainly helped in my .22. It came stock with a plenum extension piece (good) but also with a stiff hammer spring (good) that is excessively short (bad). Could not get the power up even with the adjuster all the way in until I reduced the reg to 125 bar and added 4 pvc washers to the HST. This increased power without creating hammer bounce that would have decreased shot count. In a .25 with an equally short hammer spring the shimming should be equally relevant, hence my suggestion of 4-5 washers. For reg set point you clearly need to start a bit higher than in a .22, therefore suggest to start at 130 bar.