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Tuning Uragan Compact: Factory tune vs 1/4 turn on HS shot string's STDs

Okay, it is raining outside and I have a new gun, so I did some suburban indoor shot strings.

I wanted to see if the regulator was settling in with the shot string of a magazine, it was ups and downs see screenshot, labeled accordingly.

Data Geek Stuff:

  • AGT Uragan Compact 177
  • JSB 10.34 Heavy
  • Indoors
  • 70 F

Then I thought, "Let's do a 1/4 increase and see what we get (me, myself and I) FPE and things tightened WAY up in the STD range. I started with 10 shots was like "hhhhmmm" then ran a full magazine and things got even better after another 15 shots.

Okay, I am no expert at tuning a gun by any means. However, my understanding is that the harmonically tuned your hammer spring and regulator are, the tighter your shot string. Is this correct or is my Cheeto high messing with my brain logic?

Could have my Uragan come with the regulator and hammer spring a bit out of wack, and now that I tightened hammer spring up things are where they should be, harmonically speaking?

The rabbit is me right now.





Jul 26, 2020
CA, United States
    Sure it is correct Peter. HST and reg pressure are almost always a balancing act with both needing to be tuned together. Maybe that just didn't happen (or at least not optimally) at the factory, and I am unaware of what tuning Krale does on a gun before boxing it up and shipping it out.

    I was tuning my new .177 Priest 2 yesterday. Funny thing was that I could get no appreciable muzzle velocity change with +/-2 turns of the hammer spring tensioner. Only when I changed the reg pressure could I get muzzle velocity changes. HOWEVER at the reg pressure I chose, even though the hammer spring pre-tension didn't make any velocity changes, it did make a difference in the shot-to-shot consistency and thereby reduce the extreme spread of the shot string, and eliminated flyers.

    Curiosity got the better of me so I am decided to do a 50 shot string and things opened up. However, the base seems to be in a 875 FPS at around 17.5 FPE. I will be interested to see how it performs on groups later in the week when I get a chance to try a 25 and 50 yarder.

    Here is the 50 shot string using the FX Pocket Chrony:

    If you were able to raise your FPS basically 80fps yeah the HS was definitely out of sync. Ideally you want to find the max speed then back it down 3-5% off your max speed. That's where you'll usually get the best strings.

    Also @TMH you might need to back off the HS even more to see what your looking for. Having basically the same gun as that you'll need to back out the HS essentially out the back of the plate.
    @dairyboy I think things are stable, Monday evening I ran another shot strings using two magazines (30 shots) to see if things were stable, and it appears they are stable:

    Using JSB 10.34 gr Heavy after 90’s shot, these are the average numbers off the top of my head:

    • 875 FPS
    • 17.5 FPE
    • STD 5.2
    • Extreme Spreed 19 (no shots were removed from data)

    I will do my best to try to go to get some groups this weekend to see if it is grouping well.
    While waiting for my client to send me the next batch of documents to review, which for them is bad because our contract says they get billed per day, not hour.

    So I decided to do another shot string with the Precision Ballistics 10.3 gr Mako Slugs. I have a limited number and so I only did one magazine: 15 loaded, one got FBARed, 1 not read and I would up with this with the lowest removed the buggered up the whole data string. However, I will post the original numbers for transparency sake, screenshots.

    Lastly, with the type of consistency and if Shadow can shoot slugs (maybe maybe not and I have 4 types to try (2 look #s wise promising) without having to adjust anything to screw up the pellet "setting" then I will try for dual purpose depending on conditions.

    Now for the data:

    Make Ballistics 12 slugs 19-05-2022.1652990555.png


    Here is one more post then I’ll quit boring you. Last night in my boredom I decided to see if there would be any difference in the Data between my 3 magazines, one Carn and 2 AGT using JSB 10.34 gr Hades. To answer the former no! Before is a note pad of info. It the range is open today and weather allows I’ll post groups. Haven’t touched the gun since the adjustment of the hammer spring.