RAW HM1000X .25 with lighter hammer weight, peek valve

Umair, I just wanted to point out if you change the singular variable of hammer weight to reduce the velocity from 935 to 880, the resulting state of tune will likely not be optimally balanced...meaning the extreme spread will suffer.

Once you've finished lightening the hammer, you're going to want to fine tune the hammer spring tension until you get back to the velocity knee (95% - 97% of peak velocity). That will very likely bring the velocity back above 880fps. To achieve a balanced state of tune at 880fps, I expect you will need to reduce the regulator setpoint. Or you can restrict the transfer port to achieve the same thing...I would not recommend this approach if the desired reduction were significant but in this case it's just a modest amount.

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I agree with you on this point completely. 

The problem is that it is not fx impact that I can tinker externally. 

Here I need 880 fps at lowest hst and 990 fps at highest hst to use various weights of pellets and slugs.

I understand that for 25 grain pellets I will have to make an other transfer port with a smaller size.

I further understand that I should tune the gun to that limit where the increasing of hammer spring should stop increasing fps and from there I should reduce the hst a bit to get the best tune.

I plan to readjust the reg pressure to achieve the tuning balance of reg and hst as I have mentioned above. Right now I am at set point of 145 bars. I should try 140 bars and then 135 bars to find the best balance.

Am I right sir ?

Umair Bhaur 

An experiment completed. At previous reg pressure of 145 bars with min hammer spring tension 34 grain was doing around 935fps before reducing hammer weight. After reducing hammer weight by 6 gm the same 34 grain at same 145 reg pressure at minimum hammer spring setting did 900fps and at max hammer spring tension it did around 1000fps. With the same reduced hammer weight, I decreased the reg pressure to 135 bars. Now with same 34 grain pellets at Min hammer spring tension it gives 920 fps and with max hammer spring tension it gives 950 fps. Conclusion is that I will have to take the route of further reducing hammer weight a bit and keep the reg pressure to previous setting that is 145 bars. This will give me tuning space from around 880 fps to 970 fps with 34 grain pellets. This 90 fps room will be available by just adjusting the hammer spring without disassembling the gun.

Even LIGHTER HAMMER and then a stiffer hammer spring can shorten dwell enen further, save air and lower muzzle report.



it is a BALANCE ....harder you lean on it less the tuning tricks have advantage. if nearing maxing out any PCP platform you get at some point a powerful air hog !!

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Dear Motorhead, 

One thing strange appears.

My same RAW HM1000X .25 set at 145 bars and with original hammer weight lost its power.

Now it is doing maximum of 915fps and min of 865 fps with different hammer settings with 34 grain jsb pellets. 

I sm unable to understand the reasons as previously the same setting were giving me 935fps at Min hst and around 980 fps at max hst.

Is my pro chrony is deceiving or I should look some specific area of the gun ?

Regards, 

Umair Bhaur 

Got it fixed. How? Don't know exactly. 

Just disassembled the gun and reassembled it after thorough cleaning and luring.

Light weight hammer of 60 gm.

Reg pressure 145 bars.

34 grain .25 jsb

Min hst 880fps 

Max hst 975 fps

Finally objective achieved. 

Thank you all for the support. 

Regards, 

Umair Bhaur 

I just checked and I get 70 regulated shots at 61 ftlb with 34 grain jsb in .25.

Extreme spread is 15fps but 60 shots in single digit extreme spread