SCHOOLS OF THOUGHT

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Drumsnguns

Member
Jun 14, 2016
959
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North Carolina, United States
I've noticed two schools of thought. Some guys do the tune where they tighten the HS to the point where the Power Wheel won't move then they turn back to the point where it does turn. Then I guess they set the reg anywhere they want after that.

The other school, I call the Ernest Rowe school where for a given reg setting you tighten the HS until the velocity maxes out and then slightly back it off. His method also allows for exceeding the target velocity with the HS and then pulling down to the target V with the valve.

I have not tried the maxed HS method. 

Anyone care to comment based on their findings?
 
I assume you are talking Impact?

I guess I'm from a different school. I don't tend to max out the gun, but shoot further to the center of the gun's capabilities. I've never seen the need to max the power wheel, though Ernest's method would be my choice if I were to do it. I could drive pellets near 1000 fps, but prefer closer to 830 or 850 because in my case it's more accurate. Your case may be different. 850 doesn't require maxing anything out, so never went there.
 
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I find the max HS for the given reg setting. You really don't want to shoot your gun there and call it a tune. With lets say a Dreamline, you can then back your HS down to 3 or 4 and be in a sweet spot. With an Impact, the gun has an extra trick up its sleeve by being able to control the valve. I see where it can get confusing. Why would you want to beat the crap out of your bumper with a maxed out HS setting to control velocity when you could back off the HS wheel a couple clicks then fine tune with the valve that isn't taking maximum hits. That's why pellet and slug manufacturers love the Impact. There is another step in finding your best setting and that equals more ammo. If a guy bleeds himself dry to afford one, ammo spending will finish him off. That's what happened to me in 2017 with my first Impact. I got tired of buying pellets to shoot over a chronograph. 


 
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With the old style valve adjuster with rubber ball I may have tried it just to see how it worked. The rubber ball actually was a bump stop probably had a little control on valve lift. I have no experience with that setup and wish it was implemented with the power plenum. I find the valve adjustment on the pp....just a spring.....a very very fine adjustment and can tune without even touching it. Its almost a novelty knob. I would rather have a positive stop to control lift, than another opposing force of a spring. I now leave mine on the fourth line. If 1 turn up or down doesn't get me the results I want, an adjustment of the hammer spring or reg pressure is in order.

So to me, maxing out the hammer spring would take away a large portion of my tuning abilities. 
 
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Yes talking about the Impact. I use Ernest's Method with a little bit of Matt Dubber thrown in. I start with the wheel on MAX then for the given reg setting, I turn in the Hammer Spring Adjuster screw until the velocity peaks then I just back off. Then I shoot groups at each wheel setting. I'm finding that setting 4 on the wheel gives the tightest groups.

Like I said I'm seeing where some guys turn turn the adjuster screw in to the point the power wheel won't turn then they back it off until it does turn and then I guess they control velocity by changing the the reg. I'm really not sure how that method works but was curious Perhaps this is good for hunting with heavy slugs???
 
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There are many guys in here who know WAY more about these things (PCP's) than I do but from what I've read in here, and adapted myself, is the 95% ('ish) max of hammer spring for a given reg setting. Ie; incrementally throttle up the speed until it no longer goes faster - you've likely found reg max here. Then throttle the HS back down a bit. A gun that I recently used this for - the 25 grain jsb knock outs seemed to max out at around 955 or so. 95% of that had me dial it back into the 9-teens. Didn't group well in there. I slowed it down a little - 1/8" turns on the HS and . . . it got worse. ( lol ) I dialed it back up - again - using just minor increments at 1/8" or so turns - I got it into the 920's - instantly visible grouping improvement. Cutting to the chase - low 930s turns out to be the magic speed for that gun w/that ammo.
 
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Cutting to the chase - low 930s turns out to be the magic speed for that gun w/that ammo.
Click to expand...

Im curious if how you get to that speed makes a difference in groups. Hi reg/lower hammer, low reg/high hammer Etc. or does 930=930
Click to expand...

I would jump in just to say that, in theory (from a first-order effect perspective), it should not make that much difference how you get to your desired projectile velocity. However, second and third order effects start to come into play. For example, the hammer impact force can cause vibrations that may effect accuracy/grouping. 
 
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Coming back to this topic. I tried the method by which you crank the HSTA all the way like some well known YouTubers have suggested. 

Well I suppose it’s ok if you want to get 20-30 shots. I had to turn the power wheel all the way down to 2 and it was still just blowing air. 


I started over, dropped the reg to 110 bar, did the Ernest method, found the best HSTA position and am getting 893 FPS. Groups at 50 y are between 0.2 and 0.3”. This is great. Tons of shots before refilling and super tight groups. 



 
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Guess I'm old school (definitely old), don't care for the FX adjustomatics. But, in general reference to tuning, I set the reg at a certain set point, and see where I am at around 95% of the max HST, then adjust the reg up or down accordingly. Seems to work. If the velocity is consistent, the groups are good, and the squirrels drop dead, I figure I'm done.


 
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Think it relies on missunderstanding. Many doeas not get the fact that thouse who max out the hammer on a gun like the impact, usually losen it back again when they have found the desired speed. It is more practical to max out the wheel first, if you are adjusting for high power, and then use the setting on the wheel to measure the max pellet speed. Othervise you had to turn that small allen screw on every step you increased the reg. After the wheel is maxed out you can start meassuring on setting 1-2-3, and upwards, and then loosen the set screw again when you are happy with the reg setting. 

If you in the end leave it so "max" on wheel is just below the max pellet speed you previously meassured, you have wide adjustment range on the wheel, to test for accuracy later.
 
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