FX Impact MK2 PP 25 cal - how to start tuning for power?

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bigHUN

bigHUN

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Jan 16, 2020
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L4G7X4 Canada
This is my first regulated gun and a first FX. And I am walking the learning curve with reg pressure and hammer tension - in my basement. 

The weather at my place is still shy out of winter, about 4-6 C temperature, it is not wise these days to go to a cornfield and get cold (especially me @ 60).

I am not planning to get a slug liner for now, I would like to tune the JSB King Heavy MK2's, 33.95 gr 25 cal for longest ranges possible.

I watched and following the steps in these two youtube movies, 68.Whiskey tune (Feb.2010) and Ernest Rowe (May.2019)

I did some progress so far but couple days ago replaced the stock brass TP swap to Huma dual port and the speed jumped from 901 to 931 fps (I did not targeted that speed it was just a coincidence that I was there at that moment) but with the larger port I also noticed that two magazins eated up a decent amount of air (from 230 bars to 140 bar drop). Also I think that almost ran out with Hammer Spring adjustment at 110 bar Reg Pressure.

Also today I got finally the new pin style pellet probe from a machine shop. So tomorrow start all over again from scratch.

What would be a good ballpark for chrono speed I shall target before I touch the valve-stop adjuster knob? Assume best way to start again turning out all the way to 4th line, or beyond? (btw I don't know if this new PP Impact still have a rubber ball or a spring?)

At what speed range these pellets (JSB King Heavy MK2's, 33.95 gr 25 cal) group tightest let say 100-150 meters/yards?
 
What speed you have set for best POI consistency?

Pellets and slugs?

I got currently 926 fps "flat" consistent (per 6 shots strings) with about 110 bar, power adjuster screw fully to the end (I can still turn/rotate the dial) and the valve adjuster at 4th line, Huma dual transfer port and reasonably enlarged (the original) pellet probe. So I shall be able to dial the power down (with a knob) but not sure with this hammer spring that I can dial the power up higher.
 
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How can I translate my archery tuning to airguns tuning?

I was competing FITA and Field up to 90 meters and 80 yards for a decade, I built myself jigs to help for tuning my equipment.

Before every fletching I indexed my arrows for weak/stiff spine - would this be translated to indexing the pellet/slug liner? I know the material is carbon vs steel but I am expecting to be measurable...

1585853952_15566530395e86360088fde7.85082437.jpg


Also I shoot-to-tune the arrows maximum distance I was competing, that would translate to some sort of shooting jig or rest? Also measuring/sorting pellets...

1585854101_9240056395e863695bdd565.77714518.jpg


I was reading somewhere here about indexing liners...how to do? Simple rotate the liner in certain angle sequence or anything measurable? Also I saw some people putting several orings in sandwich in between the liner and the barrel tube, I assume to dampen the oscillation when the projectile is launching?


 
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All the videos I watched all these youtube vloggers talking balancing regulated pressure and valve power adjustments.

I got it, I got to a very consistent 926 fps and I stop there, assuming if I don't need that fps I can dial down on power adjustment knob, right?

But nowhere saying shall there be more power (to buffer) available and how to get there.

In example your slugs likes the 900 fps but to find a sweet spot you had to play and test within let say +10% to -10% range, so that range I am calling "power in reserve" you don't need it but it is there (you know that now but you didn't knew when you started tuning).

Currently I ran out with a screw travel on a Power Adjuster and the Reg Pressure is about let say 120. How can I get more adjustments there?


 
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I have the mk2 700mm but not the power plenum yet, and my regulator is @160bar. When FX sends me the power plenum I will tune it to were the set at now hoping to get more shots not power at this time. When I turn the gun @920fps that’s on max in 90 degrees temperatures but I turn to power 5 and are 4 to stay @900fps, because the gun drops about 10fps for every 10 degrees so as temperatures drop I can turn my power wheel back up to 5 or max. But when it drops to 40 degrees the gun on max drops to the 870fps but accurate I just my scope accordingly not a big deal because I anticipate this to happen. I am retired and shoot in my back yard almost every day so I know what to expect. Also I shoot jsb 25gr on power min or 1 and 2 I just adjust my scope up or down its simple. This is what works for me hope that helps.
 
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I have the mk2 700mm but not the power plenum yet, and my regulator is @160bar. When FX sends me the power plenum I will tune it to were the set at now hoping to get more shots not power at this time. When I turn the gun @920fps that’s on max in 90 degrees temperatures but I turn to power 5 and are 4 to stay @900fps, because the gun drops about 10fps for every 10 degrees so as temperatures drop I can turn my power wheel back up to 5 or max. But when it drops to 40 degrees the gun on max drops to the 870fps but accurate I just my scope accordingly not a big deal because I anticipate this to happen. I am retired and shoot in my back yard almost every day so I know what to expect. Also I shoot jsb 25gr on power min or 1 and 2 I just adjust my scope up or down its simple. This is what works for me hope that helps.
Click to expand...

This what I wanted to know for the power knob. But as you sad you know now - because learn it along the line.
 
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With my new FX Impact Plenum (Originaly mounted, coming from Krale in Holland) .25 the reg was set to 100 bars.

Now, I set it to 115 bars and setup the hammer to get +/- 900 fps. So, if I want a little bit less I place the roll adjuster to 4-5 or A-B; fantastic results ...... for me.
Click to expand...

I assume for pellets the speed is plenty, but at one point you decide to go with slugs - how can you raise the fps? adding more reg pressure? or adding more hammer spring pressure?
 
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I'm surprised your at max spring at 120 bars. What does 5 give you compared to max at your current settings?
Click to expand...

I am below 120 bar in between 110 (I shall maybe put there the Edgun gauge instead), sorry for grammar - the hammer spring is out from 4th + line but the valve spring tension screw is bottomed.

I have the Huma dual port and I made the slots wider. Scroll up somewhere there is my drw
 
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Valve spring has the lines. Hammer spring is the dial on the side. I'm confused. If you have the hammer spring on max and the small adjustment screw maxed out for the hammer spring at 115 bar...you need to start over. It shouldn't take that much hammer strike at 115 bar.



Try something. Run a couple over the chronograph with the power wheel on 5 a couple more on 4 and 2 more on 3 and tell me the speeds
 
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Valve spring has the lines. Hammer spring is the dial on the side. I'm confused. If you have the hammer spring on max and the small adjustment screw maxed out for the hammer spring at 115 bar...you need to start over. It shouldn't take that much hammer strike at 115 bar.



Try something. Run a couple over the chronograph with the power wheel on 5 a couple more on 4 and 2 more on 3 and tell me the speeds
Click to expand...

Agreed, the power plenum has a hammerweight also if im not mistaken. Turn the little screw back until you see the slider move between minimum and 1/e and start over.
 
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Valve spring has the lines. Hammer spring is the dial on the side.... Ah OK, then this way, the Dial screw is bottomed...I'm confused. Tell me about :) If you have the hammer spring on max and the small adjustment screw maxed out for the hammer spring at 115 bar...you need to start over. It shouldn't take that much hammer strike at 115 bar.



Try something. Run a couple over the chronograph with the power wheel on 5 a couple more on 4 and 2 more on 3 and tell me the speeds
Click to expand...

I had a bad feel that I got to a wrong place but I just don't know how to call it, I need to quiet down my backstop box, a weekend is just at the door I will re-do the things
 
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Valve spring has the lines. Hammer spring is the dial on the side. I'm confused. If you have the hammer spring on max and the small adjustment screw maxed out for the hammer spring at 115 bar...you need to start over. It shouldn't take that much hammer strike at 115 bar.



Try something. Run a couple over the chronograph with the power wheel on 5 a couple more on 4 and 2 more on 3 and tell me the speeds
Click to expand...

Agreed, the power plenum has a hammerweight also if im not mistaken. Turn the little screw back until you see the slider move between minimum and 1/e and start over.
Click to expand...


I can still dial the knob from Max all the way around without feeling any resistance but look like not enough length on that small screw to tighten it further if I would raise the Reg pressure higher.
 
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