Harmonic tuning the FX Impact - VIDEO

That's impressive Mark! 

Here's another tidbit....the accuracy nodes can generally be found 20fps apart with 22 caliber. A good tune on one weight can often be good with a different weight as has been my experience. 

So it seems if I'm reading your results correctly, you got these results at 966 and 986fps? I'm not surprised being they are 20fps apart.

I hope this gives you tighter groups down range. Let us know please. 

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Bad news Bob, back to the drawing board with reg tune I think, my heart sank as the groups were 2+ inches at 100yards just like the instance you had!

I knew it wasn't me though as the groups from the Redwolf at 100 cheered us up a bit!

That's a nice group

Thanks Ghost,

Hi Bob. Thanks for posting the video. I am currently playing with my Impact .22 slug barrel as well, and this very valuable info. Keep up the great work!

A very good video Bob_O. I understand the explanation. Unfortunately I don't shoot slugs. I have a Gen 1 Impact and I don't feel it's up to the task. So I'll stay with MKII. If you have any comment for diabolo pellets then please share but I think I might be asking questions in a slug only Thread. Sorry if I'm out of line here.

That said, I have tried both Matt's Harmonic tune method and Ernest's Velocity method. Matt's is an interesting approach because, what is the real magical velocity of the MKII? I don't know if anyone knows for sure. Some guys swear on 900+ fps while others say anywhere from 830 -860 fps. Kinda hard to tune when that variable is unknown. So with Matt's, the regulator harmony dictates the speed of the pellet. When the groups get tightest then that's your reg. setting and your velocity, whatever that might be. I found two settings where this happened, 130 bar and 145 bar. Following Matt's video I got good results but at the cost of wasted air as he says not to mess with the valve....leave it wide open, (if I heard him right). Closing the valve both quietens the gun and conserves air as per Ernest's video. I'm using Ernest's tune now but am just going along with a guessed target velocity of 865fps at 140 bar. Now if the wind will ever give me a break.

Anyway, keep the good videos and info coming.

A very good video Bob_O. I understand the explanation. Unfortunately I don't shoot slugs. I have a Gen 1 Impact and I don't feel it's up to the task. So I'll stay with MKII. If you have any comment for diabolo pellets then please share but I think I might be asking questions in a slug only Thread. Sorry if I'm out of line here.

That said, I have tried both Matt's Harmonic tune method and Ernest's Velocity method. Matt's is an interesting approach because, what is the real magical velocity of the MKII? I don't know if anyone knows for sure. Some guys swear on 900+ fps while others say anywhere from 830 -860 fps. Kinda hard to tune when that variable is unknown. So with Matt's, the regulator harmony dictates the speed of the pellet. When the groups get tightest then that's your reg. setting and your velocity, whatever that might be. I found two settings where this happened, 130 bar and 145 bar. Following Matt's video I got good results but at the cost of wasted air as he says not to mess with the valve....leave it wide open, (if I heard him right). Closing the valve both quietens the gun and conserves air as per Ernest's video. I'm using Ernest's tune now but am just going along with a guessed target velocity of 865fps at 140 bar. Now if the wind will ever give me a break.

Anyway, keep the good videos and info coming.

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You could add a slug liner and shoot the monster redesigned at 980fps if your gun is .22.

A few minutes modifying the brass transfer port and probe will give you a big power boost.

Heavy-Impact. Appreciate the tip. My Imoact is a .25. 

The brass breech on my original ST has been oval-ed out by Ernest. When I get the chance I want to swap that onto my pellet liner. I’ll probably ruin the o-ring with the heat gun which is what keeps me from doing it. Not sure it’ll be enough. Need a 700 mm slug liner, a Huma regulator and a heavier hammer before slugs will happen. 

Sorry not meaning to hijack this thread 

Thanks for the reply, Bob. I have been sitting frustrated for 13 straight weekends with rain and very high winds. Well today that changed. 

Winds were calm. I set up and ran the valve out all the way then shot groups as I slowly closed the valve one mark ( the unpainted ones on the knob itself), at a time. Suddenly things tightened up. Measured the final valve distance at 9.95mm. I deviated from your procedure slightly and started at fifty yards. 

I got three shots into one small hole. 

Then, I set up a target st 100 y and got this group. I’ve never seen this



Pellet liner A; MKII 34.4 gn Didn’t chrony but guessing around 880-890. Three shots, 0.452” 

This was the best group but almost all the others were 0.7xx-0.9xx” personal best to date

Great helpful info here, Bob. Many thanks! And keep it coming

Cheers

KP

Thank you, Bob

I just have to reiterate that I don’t expect something this good to be consistent with pellets. Slugs maybe. But I have never shot a group like this at that distance since owning this Impact. The planets aligned for that one target. I don’t expect another target like that again but even still, it shows that there’s something at work here. With the exception of one target that measured 1.25” all the others were from 0.9” down to 0.7.” I used to be happy with 1.3”

I’ve tried several different tunings, gotten the liner and worked with indexing but this has been the best. I think you’re really onto something here. 

Cheers

KP

Hi Bob, I just watched your tuning video and reading up on these posts. Very invaluable information that you are sharing with us and I am sure a lot of people will benefit from your guidance. It made a lot of sense to what you are explaining. I will definitely try your methods shooting at 25 yards and then 100 yards. Maybe I got lucky with my Crown setting with the way it has been hitting them starlings out to 97 yards. Keep up the good work!

Alex

Hi all,



Meathead Marksman has a very good video on tuning and he uses a more experimental/scientific way of doing the tune of your impact.

Have not tried his method yet, but have a lot of confidence in his methodical way of doing it.

Will try it next week.

Great thread! I wanted to thank the OP and Bob_O for sharing his video. I am currently using Bob's harmonic video guidance to tune in some cast slugs at 30 yards with my MKII. I have been able to get the groups from 1.5-2" down to a half-inch or stacking at Bob's suggested 25-30 yard starting point. After the rains, I'll take them out to 50 and 75 yards. I have already been popping 2" spinners consistently now at 50 yards, and have been smacking old shrunken/dried tangerines out at 75 yards. Saves on slugs staring at 30 yards and doing 3-shot groups until you figure out best speeds and hardware tuning. Great Idea Bob...Keep them coming!

I just came across this thread. Biggest take away is I have been (likely others as well) making much to large of a change in my adjustments. I've got my gun shooting pretty well but I'll bet I can do better using this information. THANK BOB. I thought your video was very to the point and understandable. Some times information is presented but too much is taken for granted. Assumptions made that the reader is on the same page. Basically just the concept of small adjustments making slight changes on the harmonic curve. Makes sense.

Guys. THIS WORKS. 

Wanted to reach out with a big thank you to Bob. Finally got my new Impact .22 harmonized using the method that Roelf and Bob use. Took a while but finally got 4 shots near on through the same hole at 36m. Due to terrain constraint with the available backstop I could not use 25m. At 100m, shot 4 groups of 18mm to 21mm ctc. So incredibly satisfying after near on 1000 slugs of various types. 
The group at 36m before the final group was much larger and I moved the valve adjuster by the smallest fraction possible and suddenly, 4 shots through the same hole. 

Final settings for my tune with a 600mm Slug A liner is:

H&N 27gr .217

Avg speed 963 with an ES of 11

Reg 127, HST 15.30mm, about three turns out, Power Wheel on 5

Valve setting on 8.68mm from the little lip to the knob (slight more than 3 lines)
Thanks again. 

The slightest movement in the valve adjuster had 4 slugs go through the nearly the same hole at 36m. Less than 1:16 turn. Just goes to show how sensitive a tune can be. And it takes forever to find that spot.