Tuning A tune for testing ammo

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Corvid_hunter

Corvid_hunter

Member
Dec 21, 2019
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Ontario, Canada
I have a .25cal 700mm (Regular Superior liner with carbon fiber sleeve bonded) MKII with Power Plenum, Huma V2 transfer port and the Huma probe installed. Currently I have a good 90 bar tune that shoots 25gr Kings very well at 900fps (Max). I'm getting some slugs and Exact King Heavies to test. As the King Heavies are the heaviest of the bunch I was thinking of upping the reg to 150 bar and gradually increasing the hammer spring tension until I get the Heavies shooting around 975fps and then backing off to about 950fps. My thought process has me being able to push lighter slugs at 950+ and still being able to use the Monster Wheel to bring the velocity lower. Harmonic tuning shouldn't be as big of an issue with the carbon fiber bonded sleeve as opposed to not having it installed. Am I on the right track, or somewhere off in left field? Slugs tested will be, FX Hybrids, NSA 26.8gr, NSA 29.0gr and NSA 33.5gr. I'm not expecting miracles with the heavier slugs/pellets, but I have to try them so I know what they are like instead of doing a test and wondering what they would have been like.


 
If you're going to do that, I suggest you wait til you get some slugs to test. Max tune it on the slugs then see what you get from the power wheel as you go down.

Best results are tuning for each round but should get ya close. 

I've got a Griffin .249/.250 assortment for sale in the classifieds. Also have nsa's in the weights you mention above...lemme know if you interested at all!
 
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That’s pretty much my approach now and days, this approach is extremely versatile and can shoot many different ammo with just a turn of the dial. 


HOWEVER!!!! Please keep in mind that with versatility it’s very hard to get ES of sub 10 and SD of 2-3. That kind consistency can be easily achieved but at the price of versatility because the tune is at the edge of barrel, TP and reg/HS balance, in another word that’s dedicated tune for 1 ammo. However with the versatile tune you still should get ES of mid teens and SD of around 5-8 which will still be plenty accurate. 


Also with high reg pressure each setting on HS will have a large speed delta especially with lighter ammo so only way to fine tune is the valve adjustment which is NOT repeatable like the HS. BUT with the carbon liner the harmonic is a ton better so the need to find tune isn’t as important. My MK2PP with .25 heavy liner boned with ER sleeve and ER should tensioner simply shoots everything at almost all settings. It’s terribly boring LOL! 


another beauty of high reg tune is high efficiency and very quiet especially with 700mm barrel. With 34 grain NSA at 920FPS it’s quiet with just a FX moderated on top of the shroud. Will need a sumo if you remove the shroud and go straight carbon barrel tensioner but not bad and bout the same length. ALSO with high reg tune the low power setting are even lower which makes the tune crazy versatile, granted .25 pellets should never be shot closer than 20 yards still but it can easily get down to 500fps. 


 
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At 125bar reg on my similar 700mm sniper MK2 .25 cal. I have tried my NSA 26,8 gr slugs through my slug A liner. I have the slug power kit and Ernest Rowe dual port transfer port. The NSA were zippin around 1020 fps. my custom NOE 34.2gr decked tailless boat tails run about 930 fps. and my NOE .249-39-rf are around 37gr and run 920's.

My monster power wheel is set on 13. close to 2 lines on the valve adjuster. so your headed the right way. I tried dropping my .22 cal barrel onto the gun but I could not get the 23 gr heaviest NOE Hunter pellet to slow down enough to get decent accuracy from them.
 
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Yes, 150 bar is a good starting point for testing. You may find later on that a lower setting will work just as well for more shots per fill. Make sure you tune with PW set to max and valve all the way out, then backing off the max by 5% using the valve knob for best efficiency and tune. From that point you should be able to lower the PW and see at least a 100 FPS drop from max to min. Good luck and remember to size the slugs to the choke and also lube them for best luck.
 
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I have a .25cal 700mm (Regular Superior liner with carbon fiber sleeve bonded) MKII with Power Plenum, Huma V2 transfer port and the Huma probe installed. ...
Click to expand...

Do you have two Impacts? because I got an impression in your other post you talk about .22?

I have my .25 MK2 heavy ported DIY (7.5 mm valve port up from 6.5mm) and I don't want to buy slugs until I spend these over 6-7K JSB MK2 34 gr pellets I had collected over a year of waiting for my shooting range to open.

.25 cal 34 grain @ 132 bars I got a rough ballpark about 975 fps with ES less then 5 so this is OK for me and I just let it sit there, because I dialed the power down to #1 for my target speed of 918 fps. I believe if I want to get this my 34 grain pellets to 1000 fps I can get there with this same 135 bars. So your lighter slugs shall be even faster.

Also If you want to save on air you can go higher Reg about what you saying 140-150 and balance with VS, I did not care how much air I am loosing, I will be tethering from a fireman tank.

btw, I cannot recall seeing where you located? somewhere in GTA? I am @ L4G7X4
 
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