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Tuning FX Crown .22 First Impressions and Next Steps to Increase Power

Hi,

I just shot my new FX Crown and really like the gun. It's designed to shoot the 18 grain pellet at ~900 fps on high settings. I'm planning to use this airgun as one of my options in the next AOA Extreme Benchrest 2022 and will need to increase the power to make it more competitive. My goal is to shoot a 25 grain pellet at hopefully 940+, the projected Phase 1 activity limit after all the mods, upgrades, and increasing regulator pressure including lots of testing...The recommendations from Utah Airguns is to start with the following:

Phase 1 activities which are underway:

  • Upgrade to the HUMA Transfer Port (I ordered the gun with this upgrade) and high flow pellet probe
  • Heavier hammer spring, also from HUMA
  • Increase hammer spring by removing the stock, 2 full turns CLOCKWISE as a starting point.
  • Test fps on chrono and begin increasing reg pressure in 5 bar increments to start until peak reached, adjust hammer spring as required
  • Can go to 150-160 BAR as target maximum

Phase 2 activities TBD:

  • Consider the slug tuning kit from HUMA and heavier hammer weight may be an option

I will report the shot strings and outcomes of Phase 1 mods and testing in the next week or so but if anyone has additional recommendations, please reply. 

Steve
 

qball

Member
Apr 13, 2020
5,736
347
CA, United States
    Before upgrading all that have you tried to set your reg at 150 bars and max out the hammer spring? What you are looking for is easily achieved without any upgrade from a MK2.



    My MK2 with 600 barrel is comfortably shooting 50 FPE with 27.5 NSA slugs which requires a lot more power than pellets. Also for best accuracy try 820 to 920 fps range depending on the pellets.
     
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    Before upgrading all that have you tried to set your reg at 150 bars and max out the hammer spring? What you are looking for is easily achieved without any upgrade from a MK2.



    My MK2 with 600 barrel is comfortably shooting 50 FPE with 27.5 NSA slugs which requires a lot more power than pellets. Also for best accuracy try 820 to 920 fps range depending on the pellets.

    Interestingly enough my 600mm 5.5mm Crown MK2 couldn't get 23gr slugs above 870fps in stock form. In mine at least it seems to be that the hammer from factory is just too light.

    The max reg pressure I could open the valve reasonably fully at was 115bar, measured on a sekhmet. Anything more and velocities plummeted.

    A hammer weight sorted all that out and it's now easily getting to 950fps with those same slugs at 130bar and nowhere near max hammer. The shot cycle feels better with the lower HST too.

    I'm unsure how mine came so anaemic from the factory as I haven't seen anyone else complaining of this sort of thing. I also didn't notice anything missing or different on the various strip downs available on youtube etc. 
     
    .22 Crown Power Tuning Update:

    First, I am very happy that I was able to achieve my objective, an average of 975 FPS with the Crown MKII in .22 caliber with a 25.4 gr FX diabolo pellet. The reason I was trying to get to this speed was driven by the planned usage of the gun in extreme field target and EBR competition. I've found 25 gr pellets like speeds above 950+ FPS when going beyond 50 yards. For me, at distances over 50 yards (out to 100), .22 caliber 25 gr pellets spiral if shot below 950 FPS. In addition, I've found 18 gr pellets to shoot very accurately as well at speeds above 950 to as high as 1,030+ at distances beyond 50 out to 100 yards.

    I want to say that it may be possible to "get there" without any modes (addition of transfer port, probe, spring, etc.) as mentioned earlier in the thread, so I'm not discounting that. I did the modes at the same time as the adjustments in the following order to achieve my desired FPS with a FX 25.4 gr diabolo pellet of ~975 FPS.

    Mode 1 - I ordered the FX Crown .22 with 600mm barrel. I added a Huma transfer port to the order so this was installed by Utah Airguns. Once received, I adjusted the hammer spring maybe a full turn (it could go more) and chrono'd the gun. With the transfer port set to High and the hammer spring adjusted to 23 (highest setting) my results were as follows:

    • Reg pressure started at 110 (factory setting) ended at 130 bar. Beyond this the FPS slowed so I stopped here.
    • Average speed with 18 gr FX diabolo: 970 FPS
    • Average speed with 25.4 gr pellet - 850 FPS 
    • Adjusting the reg pressure above 130 decreased the speed of the pellets in this configuration

    Mode 2 - Installed the Huma Tuning Hammer Spring and High Flow Pin Probe. To do this, I had to disassemble the gun which allowed me to remove and better adjust the hammer spring at least another full turn. Its difficult to find the end of the hammer spring adjustment screw with it in the gun. Adjusting the hammer spring plus the heavier spring and high flow probe really opened things up!

    • Reg pressure turned to 140 bar
    • Average speed of FX 18 gr pellet - 975 FPS on power level 8!!! Previously I had the power wheel on power level 15 to achieve 975. It would be well over 1,100 FPS if set to power level 23, the highest setting.
    • MY GOAL ACHIEVED: Average speed for an FX 25.4 gr diabolo pellet - 971 average FPS on power level 23, the highest setting.

    Additional context. Since I achieved the average speed I was shooting for, I did not go higher than 140 bar on the reg, so higher speeds are possible, I think. One of the concerns I had continuing to adjust the hammer spring in the gun was not knowing when the adjustment reached the end and having the screw fall out...Removing the adjuster from the gun during installation of the new heavier spring and probe made it easier to adjust the hammer spring with full turns versus the smaller incremental turns you get with it in the gun. I watched the Ernest Rowe FX Crown disassembly video on YouTube for the first 5 or so minutes and it was easy to perform the disassembly and install. 

    The gun is very accurate out of the box and I'm considering using in the AOA EBR 2022...

    Now on to testing the guns accuracy at 50, 75, and 100 yards against a Safari, Wildcat and Thomas .22 HP. More to come...

    Steve


     

    qball

    Member
    Apr 13, 2020
    5,736
    347
    CA, United States
      Interestingly enough my 600mm 5.5mm Crown MK2 couldn't get 23gr slugs above 870fps in stock form. In mine at least it seems to be that the hammer from factory is just too light.

      The max reg pressure I could open the valve reasonably fully at was 115bar, measured on a sekhmet. Anything more and velocities plummeted.

      A hammer weight sorted all that out and it's now easily getting to 950fps with those same slugs at 130bar and nowhere near max hammer. The shot cycle feels better with the lower HST too.

      I'm unsure how mine came so anaemic from the factory as I haven't seen anyone else complaining of this sort of thing. I also didn't notice anything missing or different on the various strip downs available on youtube etc.


      Did you max out the preload first? Heavy hammer is great but be can easily make the dwell too long.
       
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      Interestingly enough my 600mm 5.5mm Crown MK2 couldn't get 23gr slugs above 870fps in stock form. In mine at least it seems to be that the hammer from factory is just too light.

      The max reg pressure I could open the valve reasonably fully at was 115bar, measured on a sekhmet. Anything more and velocities plummeted.

      A hammer weight sorted all that out and it's now easily getting to 950fps with those same slugs at 130bar and nowhere near max hammer. The shot cycle feels better with the lower HST too.

      I'm unsure how mine came so anaemic from the factory as I haven't seen anyone else complaining of this sort of thing. I also didn't notice anything missing or different on the various strip downs available on youtube etc.


      Did you max out the preload first? Heavy hammer is great but be can easily make the dwell too long.

      Yup. Did all of the usual stuff.
      The gun in factory state was simply unable to open the valve properly above 115bar. I did confirm that pressure across a few gauges too. I don't know exactly why, but can only assume the hammer was somehow made very slightly too light. The spring is identical to those in my impacts with no appreciable difference in rate.
      The 9gr hammer weight was the last option available. It sorted everything out nicely and there has been no loss of efficiency or other ill effect to suggest the valve dwell is too long. Given that it couldn't actually open the valve properly to begin with, dwell was likely super short pre weight, so I wasn't too worried making the change. Consistency has also improved vs running the light hammer with ragged edge hst.

       
      You can find pre made ones in different sizes at bagnall and kirkwood, huma air and several other sites. Just search hammer weight and they'll pop up. They are very easy to install between the the hammer and spring, but do require modifying (i.e.cutting off) the crowns spring guide. The hammer weight shaft acts as a guide in its place. 

      I don't know exactly who stocks them in the US unfortunately but I suspect most of the bigger retailers would.

      I just used a friend's spare huma weight for the maverick. It was pretty hefty (14.5gram) and long though, so I turned it down to the size/weight I wanted on my lathe. 
       
      You can find pre made ones in different sizes at bagnall and kirkwood, huma air and several other sites. Just search hammer weight and they'll pop up. They are very easy to install between the the hammer and spring, but do require modifying (i.e.cutting off) the crowns spring guide. The hammer weight shaft acts as a guide in its place.

      I don't know exactly who stocks them in the US unfortunately but I suspect most of the bigger retailers would.

      I just used a friend's spare huma weight for the maverick. It was pretty hefty (14.5gram) and long though, so I turned it down to the size/weight I wanted on my lathe.

      Purchasing hammer weights is an option. I ve done so myself once. Originally bought the 6 gram weighing FX 20271 intended for use in my Crown.

      But... since i wanted a somewhat smaller/shorter 6 gram weight (to combine with a Huma spring) , i made my own. For this particular purpose i chose brass because of its volumetric mass density being somewhat higher than in steel.

      So ... why not consider making some weights yourself, specifically to suit your own needs. Not at all that difficult, even if you re not technically schooled (like me).

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      I bought my Crown Saber MK2 600 mm barrel from SPAW. Ken set it up to shoot 24.5 gr pellets or slugs at 925 fps. Reg pressure is 150. I don't know if he changed anything internally, but I suspect everything is stock. I did add a dual transfer port and pin probe. The gun shoots very well at 100 yards.
       
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      I am not sure why one poster couldnt get his crown to work above 115 bar but sounds like something was tuned incorrectly or it had something wrong. You should be able to hit 900+ fps easily with no aftermarket parts. I have two crown mk2 both in .25 cal. I have one setup with a 700mm barrel and set at 130 bar on the reg. I have not touched the hammer pre load adjustment under the stock I have only changed the setting on the power wheel. That setup runs 25 gr. JSB at 975 fps with the power wheel at max. The other crown is setup with a 380mm .25 barrel. I adjusted the hammer preload under the stock to have just a little wiggle room with the wheel set at max. It could go higher but not a bunch. The reg is set at 155 bar and with that setup I still get 883 fps avg with 25 gr. JSB and 813 fps avg with the 33 gr. mk2 JSB. I would think you could get the same types of results with the same settings with a .22 barrel.
       
      Last edited:

      Smok3y

      Member
      Sep 25, 2018
      1,139
      49
      NC, United States
        I bought my Crown Saber MK2 600 mm barrel from SPAW. Ken set it up to shoot 24.5 gr pellets or slugs at 925 fps. Reg pressure is 150. I don't know if he changed anything internally, but I suspect everything is stock. I did add a dual transfer port and pin probe. The gun shoots very well at 100 yards.
        Same here. Stock Crown MKII 600 with no additional addons from SPAW came with 25.4’s shooting at 940, with 150 reg on high. I could flip to lowest setting and shoot 18’s at 880. It was perfect. Best shooting rifle I have owned and regret selling it. A 700mm barrel or those addons you mentioned could have gotten it higher, but my one liked 25.4s in the 930-940 range.
         
        I am not sure why one poster couldnt get his crown to work above 115 bar but sounds like something was tuned incorrectly or it had something wrong. You should be able to hit 900+ fps easily with no aftermarket parts. I have two crown mk2 both in .25 cal. I have one setup with a 700mm barrel and set at 130 bar on the reg. I have not touched the hammer pre load adjustment under the stock I have only changed the setting on the power wheel. That setup runs 25 gr. JSB at 975 fps with the power wheel at max. The other crown is setup with a 380mm .25 barrel. I adjusted the hammer preload under the stock to have just a little wiggle room with the wheel set at max. It could go higher but not a bunch. The reg is set at 155 bar and with that setup I still get 883 fps avg with 25 gr. JSB and 813 fps avg with the 33 gr. mk2 JSB. I would think you could get the same types of results with the same settings with a .22 barrel.
        Nothing was incorrectly tuned. Just couldn't get any higher. A friend who just bought one about 3 weeks after me, from the same shipment - his could go significantly higher out of the box. We opened it up the other day to see why and the only difference was his had a washer similar to that found in the impact slug power kit inside the hammer from the factory. Never seen that on any disassembly videos either. So maybe for whatever reason a batch of hammers were machined a little lighter than normal or something. Wouldn't take very much error to shave off 5 or 6 grams.
        Who knows? 🤷‍♂️ Bottom line is it now produces excellent power and consistency.
         
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        Nothing was incorrectly tuned. Just couldn't get any higher. A friend who just bought one about 3 weeks after me, from the same shipment - his could go significantly higher out of the box. We opened it up the other day to see why and the only difference was his had a washer similar to that found in the impact slug power kit inside the hammer from the factory. Never seen that on any disassembly videos either. So maybe for whatever reason a batch of hammers were machined a little lighter than normal or something. Wouldn't take very much error to shave off 5 or 6 grams.
        Who knows? 🤷‍♂️ Bottom line is it now produces excellent power and consistency.
        You never know. Theres always a chance something was incorrect during parts manufacturing or assembly that caused it to be different from the norm.
         
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