Tuning Impact Tuning - hammer spring vs reg

[bentaroh]

Tuning my .22 impact (with 70mm / power plenum) to shoot hybrids. I bumped the reg up to 125, then increased hammer spring tension until it was shooting around 960, and dialed it in from there with valve adjuster. I can increase my hammer spring preload more, and possibly decrease the reg to around 115-120 - but would this be preferable? 

Is the goal with tuning to find a nice mixture of reg / hammer spring that give consistent shot stings? Or is it advantageous to keep the reg as low as possible? From what I can tell the gun shoots exceptionally either way.

Thanks! 

 

[Kurt110]

I had the same question to answer with my Impact Mk2 PP with a 600mm barrel. I fitted the dual transfer port and pin probe which gave me a 50fps increase. I wanted to shoot 26 to 27 grain slugs up to 960fps and as low as 920fps, with accuracy coming first, not speed in that range. 


I set the reg at about 127 bar and maxed out the hammer spring, valve adjuster on line 4. Started shooting 5 shot strings to check speed and extreme spread by turning the hammer spring adjuster back by one turn at a time, for 14 turns. The ES was by far the lowest on three turns out from max, averaging 7fps, at a speed of 960 average. I have the similar question, is this a “balanced” combination? Is it efficient? I had a few HST settings where ES was 11 or 12 FPS and others as high as 30fps. 


Like yours, my Impact shoots very accurately. I used the valve adjuster by the smallest turns possible to tune the 27gr H&N slugs to shoot sub MOA at 100m. Out of 10, 4 shot groups it will be sub MOA for at least 7. 


Now, is the small ES the main contributor to this level of accuracy in the overall tune or should I try a lower hammer spring tension and accept a higher ES but have the gun under less tension, and tune from there with the valve adjuster?

 

[Glem.Chally]

I like a lower reg pressure and because I have a hammer weight it needs very little preload. Usually shoot on MIN on hammer wheel and adjust speed with the valve knob.

That's for .22 and .25, for .30 if I want to make high power I'll get into more preload otherwise I find it doesnt need it.

 

[Odoyle]

https://youtu.be/9K9uG2KOPt0

 

[tor47]

It is hard to tell what is best on an impact, shooting close to max speed at given regpressure, or user higher pressure than needed. I noticed on mine, the reg seems to be more consistent staying lower than 130 bar or so. If you are tuning for high power, it is probably a good idea to use low reg pressure to reduce vibrations, and wear on the gun. But if you shoot "standard" pellets at normal speeds, you are probably never stressing the gun anyway. Shooting a .177 which may require only 80 bar, would probably shoot as good on 110 bar, as you can usually achieve good accuracy and ES with combination of hammer spring, and valve adjuster. Many guns does not have a valve adjuster, so they often get better ES with low reg pressure. If you plan to tune the gun for just one pellet, and speed, it is probably a good idea, to leave the reg at low pressure. Ernest Rowe has a video, where he has different tunes for different calibers, and power levels, so leaving the reg where it is, make sence, as it is easier to get back to the same settings again. It is easier to adjust the hammer force, and valve adjuster back and forth, than to get back to the same setting where you are adjusting all three. Also the reg can be damaged if you adjust it to much, and are not carefull what you are doing.

 

[triggertreat]

I like a lower reg pressure and because I have a hammer weight it needs very little preload. Usually shoot on MIN on hammer wheel and adjust speed with the valve knob.

That's for .22 and .25, for .30 if I want to make high power I'll get into more preload otherwise I find it doesnt need it.

Can you say how much hammer weight you have total? Thanks! I'm thinking about pouring some lead in mine.

 

[Glem.Chally]

I like a lower reg pressure and because I have a hammer weight it needs very little preload. Usually shoot on MIN on hammer wheel and adjust speed with the valve knob.

That's for .22 and .25, for .30 if I want to make high power I'll get into more preload otherwise I find it doesnt need it.

Can you say how much hammer weight you have total? Thanks! I'm thinking about pouring some lead in mine.

I think 7 grams. Thats just the hammer weight never weighed the hammer.

 

[triggertreat]

I like a lower reg pressure and because I have a hammer weight it needs very little preload. Usually shoot on MIN on hammer wheel and adjust speed with the valve knob.

That's for .22 and .25, for .30 if I want to make high power I'll get into more preload otherwise I find it doesn't need it.

Can you say how much hammer weight you have total? Thanks! I'm thinking about pouring some lead in mine.

I think 7 grams. That's just the hammer weight never weighed the hammer.

I already do have the hammer weight that came with the PP kit, and a nylon spacer to beef up the spring, but would like to change this around with more weight and no spacer, or a thinner one. I may just go for the slug kit and be done.