Airgun Technologies Uragan 3 177 600mm Tuning

[Jfk742]

Got a new rifle and it came to me doing 1029 fps, ~24.5fpe. I got it to hopefully shoot silhouettes and HFT so it needs to be >20fpe. I probably should have gotten a different gun but here we are. I’ve been reading a bit on tuning this type of rifle and have had some input on where to start with it by some helpful members. My initial testing has shown JSB exact 10.34 are really accurate and stable at 46yds. 10 shot groups at that distance were a touch over moa, using my fist as a rear bag, forgot my sandbag….

I started tuning today. My plan was to start by cranking the HS out 3 turns and the fps dropped a whole 7 fps on average. Next I pulled the valve and did 1/8 turn in, regassed to 250b and took another 1/2 turn out of the hammer spring, fps dropped down to 906fps. After a 10 shot string I had an es of 15. I put a 1/2 turn back in on the HS and the velocity shot up to the 940’s. I decided to get back into the valve and lower the setting a little more, though I started to turn the valve OUT (ccw) by accident then turned it in another 1/8 turn. After putting it all back together my fps went up to the high 960’s, I didn’t bother shooting more than a few shots and had to put it away for another day.

My initial impression is that I can get to >20fpe, with a stable enough shot string, es and sd, hopefully with no more than a little fiddling with the valve and HS. I was shooting at 12 yards and everything was going in the same hole but that’s really no indication of accuracy ime.

My plan is to get the speed down some more with the valve and then tune the HS tension over the course of a few days, letting the rifle sit between adjustments.

I have zero experience with a balanced valve and only slightly more with a Mrod from about a decade ago, I’m green to say the least. Any input is appreciated!

 

[greenbeans]

This is what the U3 is capable of in terms of ES/SD:

Not sure whether you can get that right with a very low reg setting but you should be able to get somewhat close. For that to happen you have to accept how a balanced valve works though, which means you can’t use the hammer to fine tune the speed. You want the valve to open fully every single time, everything else is not going to be this stable. To find the right hammer setting doing this for a given reg pressure, turn the adjuster out until it doesn’t open. You’ll hear it and note a significant drop in fps once that happens. Then turn the hammer adjuster back in a 1/4 turn at a time. Once speed doesn’t increase anymore you’re there, maybe give it another 1/8-1/4 turn beyond that point to be safe. That’s it. FPS are 100% controlled by reg pressure.

 

[Jfk742]

I tried turning it out until it wouldn’t fire but that only left me with 1.5 threads of engagement in the block, that was before adjusting the reg. As it came from Talon it was about flush with the block, maybe 1/4-1/2 turn out. I also saw a big dip in velocity (~100fps) with it turned way out, is that typical? I didn’t shoot it much like that though. With the HS a few turns out from flush it’s much more quiet, like 7-8db(using my buddies decibel meter) seems over gassed when the HS is flush. I should have some more time to play with it next week.

 

[greenbeans]

Yeah they come fairly overhammered as long as the setscrew is still grabbing the adjuster you’ll be fine but yeah, could be that the reg is so low that the hammer can’t be lowered “enough”….

100 fps is very normal once the valve doesn’t open fully anymore. Another half turn and you’ll be another 200fps lower and another and the valve won’t open at all.

 

[Jfk742]

Ok, reread your instructions and realized I misunderstood. I definitely found that drop off. With my initial reg adjustment I was in the 940’s after turning the HS in a 1/2 turn from the drop off in speed. I think I blew it on the next reg adjustment with turning the screw the wrong direction initially, given velocity increased a few fps. I had the regulator valve body, locking nut and adjustment screw all marked but sharpie almost immediately came off when I stuck the reg back into the gun. I may use a scribe next time so I don’t have to worry about marks being wiped off.

Another thought, would shrinking the plenum volume help with shortening the air impulse at the shot? I have a loose understanding of how the balancing works in regards to the valve, not sure if that idea is even viable.

 

[greenbeans]

No worries hmm reducing plenum might help you to get down further but you’d need a pretty robust insert that can withstand the forces at work. I’d try to play with reg a bit more first, seems like you’re almost there. Maybe another 1/8 of a turn or a tiny bit more will do already… but I know, uragans are amazing guns but a pain to tune… on the bright side, once they’re tuned they’ll hold the tune forever.

 

[Jfk742]

Welp! We’re getting closer. I’m backed out 3/8 of a turn from factory and my fps with a jsb 10.34 is 877 fps. All pellets i have aren’t preforming terribly well at that power. Some fooling with HS tension helped with group size but I’m not happy with them and I’m assuming the reg isnt either. Degassing right now and will bump the reg a 1/16 of a turn in and see if that will help get me in the ballpark for accuracy and keep me under the power limit. The local range has an airgun only day tomorrow, gonna try and make that if i can get the gun back together and the wife’s permission.

 

[greenbeans]

If your reg was at 90b from factory 3/8 lower should put you really low… like 50-60b low. I think thats (way) too low for the reg, I’d go 1/8 in at least…

On other thing: did you ah e to carve out some part of the stock to make the hammer adjust fit? If not your hammer is probably still too much. On the U2 I had to take out quite a bit to make it fit at 90b tune with a properly balanced hammer…

 

[Jfk742]

If your reg was at 90b from factory 3/8 lower should put you really low… like 50-60b low. I think thats (way) too low for the reg, I’d go 1/8 in at least…

On other thing: did you ah e to carve out some part of the stock to make the hammer adjust fit? If not your hammer is probably still too much. On the U2 I had to take out quite a bit to make it fit at 90b tune with a properly balanced hammer…

I went in a 1/16 of a turn and the velocity is still low. I want to be around 900-930 fps with the jsb 10.34’s. Current average is 883, ESof 5, another 1/16 or a little more should get me there (velocity wise). Assuming the fiddling I've done tracks with what im seeimg on the chrono, I’ll be at a 1/4 turn out from factory setting after this next adjustment. Even at the current setting I’m able to back the hammer out enough to see a noticeable drop off on velocity. I’m about a 1/2 turn in past the point where i see the velocity level off, also noticed the ES and SD tightened up. The shot is a little louder this way but the groups and ES/SD are more favorable.

 

[greenbeans]

I went in a 1/16 of a turn and the velocity is still low. I want to be around 900-930 fps with the jsb 10.34’s. Current average is 883, ESof 5, another 1/16 or a little more should get me there (velocity wise). Assuming the fiddling I've done tracks with what im seeimg on the chrono, I’ll be at a 1/4 turn out from factory setting after this next adjustment. Even at the current setting I’m able to back the hammer out enough to see a noticeable drop off on velocity. I’m about a 1/2 turn in past the point where i see the velocity level off, also noticed the ES and SD tightened up. The shot is a little louder this way but the groups and ES/SD are more favorable.

Sounds good!! Yeah I basically adjust hammer until I’m right at the point of fully open valve and the. give it another 1/4 turn or bay be a bit more. As for reg, 1/4 down from 90 should get you to 70-75b, which is probably still ok with the reg.

 

[Jfk742]

What are you looking/listening for in regards to HS tension screw adjustment? Do i look for a plateau in speed then 1/4 turn when the fps flattens? There seems to be a lot of nuance with the balanced valve. Are there different spring’s that i can get? It would appear to my untrained eye that I’m within the adjustment range given my experience with this gun so far.

Sounds good!! Yeah I basically adjust hammer until I’m right at the point of fully open valve and the. give it another 1/4 turn or bay be a bit more. As for reg, 1/4 down from 90 should get you to 70-75b, which is probably still ok with the reg.

 

[greenbeans]

What are you looking/listening for in regards to HS tension screw adjustment? Do i look for a plateau in speed then 1/4 turn when the fps flattens? There seems to be a lot of nuance with the balanced valve. Are there different spring’s that i can get? It would appear to my untrained eye that I’m within the adjustment range given my experience with this gun so far.

Yeah basically plateau in terms of fully open valve, then another 1/4 to be certain that it opens fully even with a bit creep. “Plateau” means the point where a 1/4 turn only gives you 2-3 or maybe 5 fps more. That’s not because you still can open the valve more, those tiny increases are because you smash the valve open with (too much imho) force.