I need some help with my Impact MK2

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K

Kgphotos

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May 31, 2015
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CA, United States
My Impact MK2 has been great shooting pellets (18.3 JSB). Now I am experimenting with NSA slugs and a slug liner. My gun is MK2 in .22 with a 700mm barrel, all factory stock. I have watched all the videos on tuning that I can find. My goal was to power tune the 24.8 grain slugs into the mid 900s and then slowly harmonic tune down in velocity until I find the sweet spot. 

My problem is that I can not get past 900 with any setting. I have the power wheel set to max and have adjusted the pre-load up to the point that the power wheel won’t turn and then I backed it off a bit so that the power will turn smoothly again. The valve adjuster is open all the way passed the fourth line and I have experimented up and down the other lines. I have played with the regulator set from 130BAR up to 165 BAR. throughout all that, all I can get is about 900 FPS with the NSA 24.8 grain slugs. I have used both the .217 and the .218 diameter slugs. I even set up a second chronograph to verify the velocity and both chronographs are within about 5 fps of each other.

I am wondering if my regulator gauge might be off and I’m not really up to 165 BAR. I sure thought I would get higher than 900 fps at that setting. Does anybody know if the regulator gauge and the tank gauge are interchangeable? I was thinking about swapping them to see if they still give me the same readings.

My other thought is that my regulator is not working properly. The velocities I am getting are very consistent. The extreme spreads and standard deviations I am getting are really low; like an SD of 3 over a 10 shot string.

I would love to hear anyone’s opinion or any advise. Thanks,

Kenny




 
So before diving deeper, into new parts or modifying existing ones, the quick and easy validation is to simply turn your reg up while shooting over the chrono with your hammer spring maxed out. When your velocity peaks and starts to drop off with more pressure you know you're maxed out with that configuration. Go in small increments and keep track. Should be easy enough to do, and doesn't require your gauge be perfectly accurate etc. 

I hope that helps/makes sense. 
 
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One important thing to check before doing a bunch of testing is port alignment. When I first got my ImpactX it was doing the same as your's as far as power went. I discovered that the ports were nearly half closed off because of the cocking rod length was wrong.

To check port alignment, clearly mark the pellet probe where it is seated into the breech of the brass transfer port. I used a razor blade and scored the metal and marked that with a lead pencil to highlight the score. Then, pull out the barrel out of the rifle and also remove the pellet probe. Now, with the barrel and probe in hand, put them back together and see if the probe hole and transfer port are aligned with each other. 

If they are not aligned there's two fixes. Opening the probe's hole is one, and the other is adjusting the cocking rod length. More on that later, if need be. 

Now that everything is aligned, test for maximum speed with the regulator adjustment as STO explained.

(Only do one modification and test at a time to verify your results of your mods.)
 
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IME a stock impact will not shoot a .22cal 25gn + slug over 900-910 fps without modifications. 

You need to go light in your slug choose or make modifications to your impact, whatever fits better for you. My Choice will be go lighter, today you have may many options, when some old timers start with slugs, options were just not there (lighter and good slugs), FX Hybrids, NSA and H&N 

Anything 23gn or less should be fine
 
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Thanks for everybody’s input so far. I don’t really want to modify the rifle beyond what was intended in the design. In other word I don’t want to take it to the “ ragged edge” of performance. I just thought from videos I’d watched and posts I’d read that my rifle would be in the 930-940 range in its factory stock condition with the 25 gr. pellets/slugs. If 900 fps is tops then I will be happy with that and enjoy that my NSA slugs have a BC that is about double what my pellets have. I will also try some 23 grain slugs and see how they do. Thanks again for everybody’s time. I really appreciate it.

Kenny
 
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Thanks for everybody’s input so far. I don’t really want to modify the rifle beyond what was intended in the design. In other word I don’t want to take it to the “ ragged edge” of performance. I just thought from videos I’d watched and posts I’d read that my rifle would be in the 930-940 range in its factory stock condition with the 25 gr. pellets/slugs. If 900 fps is tops then I will be happy with that and enjoy that my NSA slugs have a BC that is about double what my pellets have. I will also try some 23 grain slugs and see how they do. Thanks again for everybody’s time. I really appreciate it.

Kenny
Click to expand...

25gn pellet, will be like 30-40fps faster than a 25gn slug, slug have more surface in contact with the barrel. 
 
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I do this work with a li-ion rotary tool and a carbide burr, second one from the right in pic ⑲. Single cut burrs are for non ferrous metals while the double cuts are for ferrous.

You want to flare the entry of the brass port to cover the 7mm hole that feeds it and then elongate the port forward about 2mm without making it wider. Never make it wider.

Then open up the pellet probe to be larger than the brass port. You want smooth airflow with less resistance.

Polish the area last using a felt tip and red polishing compound.

Use low to medium speed when removing metal for best control. Light pressure and a tight grip. Polish at high speed.

When done correctly you'll get the same velocity at about 30 bar less pressure or have much higher velocity at the same pressure. 22cal only, larger calibers will benefit less as the caliber goes up.

1572045775_9393476105db383cf3e8b71.27592898_1566849471_231067135d6439bf5cb1d1.45688243_61BMycI...jpg
1570814052_3612213255da0b86475d435.16036272_Port1 - (2).jpg
1570814052_18948973155da0b864a24ad3.38412677_Port2 -.jpg

 
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My Impact X will push redesigned .22 Monsters at 900 with the reg. @110 BAR.



Barrel inlet flared and polished, probe opened up and polished on bottom , and Delrin C3 bumper installed. Hammer wheel on max, valve stop between 3 and 4 lines out.



FX Hybrid 22 Gr. Slugs run at 880 using my Monster pellet settings with plenty of room to get into the mid 900s.

Forgot to add, 700mm barrel.
1577119284_8866366275e00ee346ac1f4.59810963_20191222_152728.jpg
1577119285_15802215055e00ee35cf1a44.27230943_20191222_152653.jpg

 
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