Impact tuning via regulator

[Drumsnguns]

I have watched quite a few videos on Impact tuning and the one that really struck me was Matt Dubber's video. He advocates tuning by starting with the regulator's effect on gun harmonics. And it worked for me.

When it comes to tuning, the Impact has a lot of variables. You should only tune by adjusting one variable at a time and the reg. pressure has the biggest affect on harmonics and group size. So that's where you start. Determine this first and you've taken care of a big chunk of the tune process.

I followed Matt's video and photographed all of the targets to show what different reg. pressures do to groups to give a visual of what happens.

All other variables were left alone for each reg setting. I used settings from my initial tune so the hammer spring setting was on MAX with the spring adjust screw at 15.66 mm. Valve was wide open at 4 lines.

I turned the regulator down to 120 bar to start, shot groups then went up 10 bar each time and shot groups. The gun was refilled after each Bar setting change to 220 Bar.. "NOTE" Be sure to always remove the cylinder and empty the gun before adjusting reg pressure. It's OK to raise the pressure, (counterclockwise), with the bottle attached but I do it for all so I don't forget but that's just me.

I set targets out at 77 yards and shot groups at 120 BAR, 130 BAR, 140 BAR and around 150 BAR. I left all other setting alone. Ammo was King Heavy MKII using the STX Barrel liner "A"

I use HUMA gauges for both the cylinder and the regulator. Much more accurate than OEM.

RESULTS

120 Bar 

1.75" Ave group

826 fps Ave

130 Bar

1.247" Ave Group

832 fps

140 Bar

1.282" Ave Group

850-60 fps

150 Bar

0.95" Ave Group

900 fps



After you determine the reg. pressure, you then adjust the HS screw for highest velocity and then adjust the valve for highest velocity and then you're done. 

For grins, I decided to try shooting groups on PW 4, 5 and A. Here's the target for A which was best. Think I'll leave it there for a while. 

0.79 at 75 yds. 10 shots, 890 fps., 150 Bar. The hole at the far right, at first, looked like a flier after the 4th shot, so I measured 0.49" excluding it but I think I'll include it and say 0.79" but 9 shots went into a hole measuring 0.49" I think that's pretty darned good for this gun. And as always...this is my gun.....your mileage may vary.

I hope this helps some new comers to the Impact and I give all credit to Matt Dubber....watch his video. Cheers and Happy New Year! KP

https://www.youtube.com/watch?v=0B2doKk47BE

 

[Bob_O]

Thank you for the detailed yet concise post Drums!!

 

[ackuric]

Well is it possible the progression of better groups being you were just warming up your shots? If so each group getting better was likely more a reflection of that than the pellet speed, as I think that is quite the extreme variance from 830 to 900 fps being almost double the group size...would love the test to be done backwards to cross verify, additionally a chronograph showing any crazy variance in velocity (es) from shot to shot would be nice for this test. 



If I am wrong and it was 100% reg settings then I apologize, either way congrats on your findings so far! That last group was really superb!

 

[edosan]

That Match my personal testings, redesigned and mkII and similar pellets (new ones) will group better on speeds over 900fps (on the impact X 700mm barels), under that speed they still group good tho, but not as good. 
Thanks for sharing!

 

[Drumsnguns]

Acurik this is the second time I’ve done this with similar results . The first time I think around 130 bar the groups tightened up and then got looser at 140 then tightened to the best group at 150. This time it didn’t seem to do it. I was hoping it would so I could just set to 130 and not have to recharge as often. Actually I think the final reg pressure was like 148 Bar. Who knows what the real pressure actually is with these small, cheap gauges

I was hoping to get the rifle shooting best at 130 to save air but it really likes shooting around 890-900. At the A setting it shot the best group at 889 ave. So that’s where it stays for now. 

I did shoot at 150 Bar to start where groups were tight then went to 120 where they opened up as posted so I don’t think anything was warming up. I didn’t bother to post the start but the groups were just slightly looser than the finish at 148 so maybe around 145-148 it’s best and at 150+ you start seeing things start to loosen up again. I’d be curious to go over 150 but don’t trust the o-rings to hold.

I’d Be interested to see what other guys results are. That’s why I posted. 

 

[AirSupply]

My results are very similar. I think the new heavy pellets like the King Heavies and the Redesigned Monsters need the quick spin rate the higher velocities give them. The .22 redesigned monsters lose stability under about 900fps The people who say they are stable at slower speeds are nearly always shooting at short distances before the pellets become unstable. +1

 

[Drumsnguns]

AirSupply,

With this setting or rather the velocity range of 900+ fps with MKII and the X barrel I have gotten my absolute best groups at 104 yards with the reg at 150 bar and the velocity at 915 fps

Two 8-shot targets both measuring at just under 1.2" or 1.18". I also have a target at 100 yards with the reg at 145 and the velocity at 887 measuring at 1.28" for what looks to be 8-10 shots back in August.. 

You might be right...and maybe it's the barrel and velocity more than the reg. I had better results with the reg at 120 bar and a velocity of about 830 with the old Smooth Twist barrel. What Matt says in his video is a compelling argument for regulator tuning though.

I originally tried this tuning back in August and kept the targets and a note book. I'll go back and just post some figures if anyone is interested. Might be a few days though.

 

[tor47]

On Matt Dubbers facebook page, there is a post where he test slug liners at FX factory(I think), where he shows different groupings with the same velocity, but different reg pressures. Even he was testing slugliners, the basics should be the same for pellets.

If you want to cover "everything", you can pick a velocity range (say from 850, and all the way up to 920 if you like). So you then start with the reg pressure which gives you max speed a liltle more than 850, and adjust hammer down to 850 speed. You then can raise pressure 5 bar in steps (10 bar may be a litle big step if you want to cover "everything") and start from new max velocity and again adjust downwards again with hammer. You will slowly find out as you increase regpressure there might not be a point of adjusting all the way down to 850 anymore, as the extreme spread will get to high. But instead you will cover a velocity range in maybe 50 fps downwards from every new max speed. It will be time consuming as you have to test fire every velocity, and pressure for groupings. But having an impact should make it much easier

 

[Drumsnguns]

tor47, what you describe reminds me of Ted's tuning method video.. Definitely worth investigation!

 

[Drumsnguns]

I wanted to post numbers from the first time I tuned via regulator back in September. So here they are. I forgot to note the distance but pretty sure around 60 yards give or take.Valve at 4 lines and HS screw at 15.72mm for all.. Three to four groups each, then averaged. MKII.

I took more time with this one and went for 5 bar increments. afterwards I optimized hammer spring for the reg setting I chose to go with.

Reg.=120

Vel.=830 fps

Groups= 0.75"



Reg.=125

Vel. = 840 fps

Group = 0.91



Reg. = 130

Vel. = 860 fps

Group = 1.02"



Reg. = 135

Vel. = 882 fps

Group = 0.93"



Reg. = 145-150

vel. = 905

Group = 0.72"



Conclusion:

120 Bar had good groups (second best) @ 0.79"

145-150 Bar had best group, @ 0.72 

Nice bell shaped curve.

So maybe two harmonic points for my gun?

The most recent tune on 1/1/19, the 120 Bar groups were not so good; maybe me not shooting as well as in Sept. or the fact I was shooting further out I was trying to beat the setting sun as well. May have to repeat and go for 2 out of 3.

Anyway...just passing along info for what it may be worth.

 

[ackuric]

Nice drumnguns, your results are more in line with what I'd expect...really marginal difference more likely to be the shooter than the rifle...certainly in OP's test. JMO!

 

[tor47]

Interesting stuff. I believe you are using max speed on every reg setting? From a harmonics point of view I am curious what would happen if you adjusted down the speed a litle with less hammer force. Like if still shooting at 830fps at reg with 125 or 130 bar. I am just thinking out loud a litle here: 

As I understand barrel harmonics, the muzzle flips, or stay calm in maybe millisecond intervals. So hitting the exact moment where barrel is calm would be just random luck finding it at the max speed for a particular reg pressure (but to be honest that is why we try different settings, so nothing wrong in that). But let us say in 50 percentage of your test shootings with different pressures, the barrel is about to calm down but is there not yet on pellet exit. Adjusting down the hammer spring in thouse cases, and delaying the pellets exit, might lead to the pellet exiting the barrel on a calmer point in time. If on the other hand the barrel just have been calm a few milliseconds before pellet exit (the other 50 percentage of the test shootings), delaying the exit would in that case make it worse. Since we obviously can not increase more speed than already maxed out, the only way to fintune for a given pressure is to go down on speed. I know pellet speed will fluctuate more if adjusting to much below max speed, but finding a more calm point in time in the barrel harmonics behavior might lead to better end result anyway. I may be wrong in my thinking though

 

[Drumsnguns]

The "A" target (0.79")I shot at 75 yd was shot at 148 Bar and on the power wheel setting "A" which is like Power wheel setting 5 but maybe more of an in between like 5.5 if that makes sense. I think it might be better than Max. I need a good day and some free time to shoot more with it set there.

 

[edosan]

Try @ 810 - 820 fps, to my surprise they group very good too at that speed

 

[DanT55]

Interesting. So the IMPACT doesn't have the plenum volume to drive the MkII to 900+ with a lower pressure so it needs a higher reg pressure to achieve these results?

Seems like a lot of wear and tear on the gun at this setting but it does improve the groups. 

Regards,

DT

 

[Drumsnguns]

Can't really answer your question regarding plenum volume and velocity Dan. I do know that Ernest had created a plenum extension for the Impact. Might direct that question to him.

I'm not really happy to rack the gun to that level but if it groups best there then there it will stay. I will try the 810 vel when the weather starts to cooperate. It's winter and the weather is not good.



KP