FX Maverick Tuning

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Chukar60

Member
Mar 15, 2022
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Idaho, United States
I need some advice, knowledge or experience on tuning a Maverick 22.
I recently converted my Maverick Compact 25 to a 22 with a 600mm barrel.
I have been struggling to get JSB 18.13’s to deliver the consistency I am accustomed to with the gun in 25 cal.
Found a full tin of .22, 25.39 jumbo monsters in my collection and decided to give them a try.
With the hammer at absolute max the gun tops out at 115 bar giving me an average of 820 fps.
Am I incorrectly assuming that the stock hammer should have handled the job of shooting these at 880-900 fps easily?
I put my 25 cal hammer weight in and got it to an average of 905 @115 bar. I backed off the hammer until I was at 880 fps and the gun sounds good and is shooting SD of around 5. I did not try to tune it any finer because I cannot quit believing there may be something wrong in the gun
Thoughts?
I wanted to check here before I go looking for a problem that may not exist.

Thanks in advance for any help or thoughts.
 
Chukar60 said:
I need some advice, knowledge or experience on tuning a Maverick 22.
I recently converted my Maverick Compact 25 to a 22 with a 600mm barrel.
I have been struggling to get JSB 18.13’s to deliver the consistency I am accustomed to with the gun in 25 cal.
Found a full tin of .22, 25.39 jumbo monsters in my collection and decided to give them a try.
With the hammer at absolute max the gun tops out at 115 bar giving me an average of 820 fps.
Am I incorrectly assuming that the stock hammer should have handled the job of shooting these at 880-900 fps easily?
I put my 25 cal hammer weight in and got it to an average of 905 @115 bar. I backed off the hammer until I was at 880 fps and the gun sounds good and is shooting SD of around 5. I did not try to tune it any finer because I cannot quit believing there may be something wrong in the gun
Thoughts?
I wanted to check here before I go looking for a problem that may not exist.

Thanks in advance for any help or thoughts.
Click to expand...
Have you tried lowering a hammerspring tension?
 
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(F)Airgunner said:
Have you tried lowering a hammerspring tension?
Click to expand...
Yes.
I started out with the hammer maxed out with the reg at 80 bar and worked my way up 5 bar at a time. When I got to 115 bar it plateaued at 820 fps. 120 bar and velocity dropped slightly.
I reset the 2nd reg to 115 and dropped the 25 cal hammer weight in it and it shot an average of 905 for 10 shots. I had to lower the PW from 7 to 5 before I got any drop in velocity so clearly the heavier hammer was having the desired effect.
My concern is that I didn’t think I should have to put the heavier hammer weight in to get to those numbers with the 25.39 pellet. I could see it for a slug but not a pellet.
I have no experience with any .22 pellets except the JSB 18.13’s. So I may be wrong in thinking that the stock hammer would handle the job.
I am just not wanting to go digging for a nonexistent problem if my assumption is incorrect.
 
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Chukar60 said:
I need some advice, knowledge or experience on tuning a Maverick 22.
I recently converted my Maverick Compact 25 to a 22 with a 600mm barrel.
I have been struggling to get JSB 18.13’s to deliver the consistency I am accustomed to with the gun in 25 cal.
Found a full tin of .22, 25.39 jumbo monsters in my collection and decided to give them a try.
With the hammer at absolute max the gun tops out at 115 bar giving me an average of 820 fps.
Am I incorrectly assuming that the stock hammer should have handled the job of shooting these at 880-900 fps easily?
I put my 25 cal hammer weight in and got it to an average of 905 @115 bar. I backed off the hammer until I was at 880 fps and the gun sounds good and is shooting SD of around 5. I did not try to tune it any finer because I cannot quit believing there may be something wrong in the gun
Thoughts?
I wanted to check here before I go looking for a problem that may not exist.

Thanks in advance for any help or thoughts.
Click to expand...
What are you trying to do? Shoot the jumbos or the 18.13's. I'm going to guess you might be able to do both, I changed a .25 sniper to a .22 compact, I left in the .25 hammer weight, put in a slug probe, not pin, and left the barrel on pellet. Here's my theory on the probe, WHO CARES how much air is going though the probe, you want max air flow but not so much as the slug port, using the slug probe reduces the turbulence/restriction of the air flow. I've tuned my Mav for 21 gr. RMR/FX Hybrids. My HSA is about 19.86mm OAL, 125bar on #2
 
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HogKiller said:
What are you trying to do? Shoot the jumbos or the 18.13's. I'm going to guess you might be able to do both, I changed a .25 sniper to a .22 compact, I left in the .25 hammer weight, put in a slug probe, not pin, and left the barrel on pellet. Here's my theory on the probe, WHO CARES how much air is going though the probe, you want max air flow but not so much as the slug port, using the slug probe reduces the turbulence/restriction of the air flow. I've tuned my Mav for 21 gr. RMR/FX Hybrids. My HSA is about 19.86mm OAL, 125bar on #2
Click to expand...

Trying to shoot the 25.39’s. I have them shooting with the 25 cal hammer weight.
My question is should the gun be able to shoot them with the standard 22 hammer weight
 
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Chukar60 said:
Trying to shoot the 25.39’s. I have them shooting with the 25 cal hammer weight.
My question is should the gun be able to shoot them with the standard 22 hammer weight
Click to expand...

No . The factory 7g hammer is not enough weight to shoot heavy pellets and only leads to frustration.

Keep using your 13g hammer. If it sounds good and is hitting 880-890 fps w a 5 fps deviation you should be gtg .
 
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Headshots said:
No . The factory 7g hammer is not enough weight to shoot heavy pellets and only leads to frustration.

Keep using your 13g hammer. If it sounds good and is hitting 880-890 fps w a 5 fps deviation you should be gtg .
Click to expand...
Took the gun to the indoor range and it is shooting fabulous. I was just wanting to make sure I did not have an issue with the internals.
I was very pleased with its consistency and how settled the gun was with the heavier hammer.
Ready for the indoor league shoot tonight now.
 
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DonaAna1 said:
You need the heavier hammer. You converted your .25 compact to a .22. It should have had the heavier hammer anyway.
Click to expand...

I have 3 barrels for this gun. One in 25 Compact, one in 600mm 22 and another 22 compact. So I did have the 25 hammer weight already. I had never attempted to shoot pellets heavier than the 18.3 JSB before. Now I know.

thanks to all for chiming in on this.
 
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