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The ImpactX experience, jsb .217 knockouts

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H

Hunter82

Member
May 2, 2020
40
2
MA, United States
I am guilty of chasing white rabbits, I have "upgraded" my ImpactX to current production mk2...I think..

In typical Tarantino style ill share the end of the story first. I am now consistently shooting unsorted/uncleaned .217 JSB Knockouts at 975fps dime size groups at 50yards, with a new 700mm superior liner that needs braking in. At 75 yards it opens up to a quarter. I am happy.... Just minor tunes from here out... fingers crossed.

The gun I started with was a ImpactX .25 600mm stx. It has evolved into a FXpower plenum, mk2 gauge, FX580cc bottle, 700mm superior, DonFL sumo, Huma transfer port, Huma single shot, NSA probe, money pit... This "money pit" does not include the include the K&L "cosmetic" parts, extra mags or optics, I am just trying to focus on what it takes to shoot the knockouts. I really could have saved time and money just buying a new mk2 impact, damn rabbit.

This upgrade started with the PP and 700mm then turned into a domino effect of problem solving. With a 700mm STX pellet A, I started the tuning and ran the .216 .217 KO at various speeds. The .217 grouped better across the board. The groups seemed to get tighter as the speed increased (all testing done at 50yards). I wish I documented this process better, sorry I don't have actual numbers. At this point I am grumbling at my Power Plenum because it is now set at 145bar offering me zero air savings, so after reading a ton about transfer ports here I thought I'd give it a shot. I didn't want to modify my only .22 TP so I ordered the Huma Set (probe and TP). The Huma TP style has dual elongated ports with a "slug catcher" between them. The process of removing the factory TP and installing the Huma for me involved a blow torch ac the factory TP was loaded with black loctite. If i remember correctly I gained about 10fps, and more mag issues. The Huma probe would catch the magazine as it traveled rearward and it would tilt the KO slugs when feeding. So I ordered the NSA adjustable pin probe. This did nothing for my Mag issues, it had a tendency to turn the slugs sideways in my mag. I was unable to find the K&L single shot loader that i loved in .25 for the .22, out of production maybe even discontinued. I settled with the Huma single shot hinge style. 

So if this is the end of the road in my journey to shoot JsbKo well out of my impactx, I ended up with a few extra parts, 700mm stx, 2 sideshotFX plastic mags, huma probe, and a set of gauges. When/if I switch back to pellets hopefully the only thing I would have to do is swap the NSA probe to the FX probe and ill be able to use the mags again. I am done chasing the white rabbit, I am done messing with this gun. My modifications have created a bench gun that has real potential for long range, but not something i want to bring hiking anymore. I have been thinking about buying a wildcat for that purpose, but with all the extra impact parts it feels like a waste. I hope my experience helps some of the new guys plan their upgrades, save some money, and dissolve some of the hype. 


 
I can't even begin to tell you how many times, and in every hobby I've had, I do the exact same thing as you have done with your Impact. I have now coined it the A, B, C, buying tactic. I start out wanting gun "A". Then after learning a little bit, and wanting more, I buy gun "B". Gun "B" will last just long enough for me to find out what is really going on. Then, you got it, I buy gun "C". Usually the price of gun A, and B covers most of the price of gun C.

I would love to tell you that I have learned my lesson, but unfortunately, I seem to be a very slow learner, and part dumb ass! The collection still grows! LOL What can I say?

I hope you catch yourself "learning your A,B,C's"

Eamon
 
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Hunter82, I have what sounds like a similar Impact evolution from an X to an MKII. I moded my TP 1mm to make it oval and notched the probe too. Got 30fps out of it. Just for the heck of it I bought the NSA probe to try it, no change in FPS. That black loctite was a b*^#! to get off. Shooting the KO .217 @ 960 has me MOA at 100. My reg is set @ 95bar. Up to this point after 3-400 slugs through it with no cycling issues with any slug I tested, then things changed, just like that, boom, the next magazine wouldn't feed slugs. After a few minutes of Why? I discovered that my barrel thumb screw had come slightly loose and the barrel had moved forward a couple mm and the slugs were "dropping" a bit so the feed was angled, no go. Re-seated the barrel so the rear brass TP was flush with the breach and bingo, no feeding problems. Just an idea.
 
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Hunter82, I have what sounds like a similar Impact evolution from an X to an MKII. I moded my TP 1mm to make it oval and notched the probe too. Got 30fps out of it. Just for the heck of it I bought the NSA probe to try it, no change in FPS. That black loctite was a b*^#! to get off. Shooting the KO .217 @ 960 has me MOA at 100. My reg is set @ 95bar. Up to this point after 3-400 slugs through it with no cycling issues with any slug I tested, then things changed, just like that, boom, the next magazine wouldn't feed slugs. After a few minutes of Why? I discovered that my barrel thumb screw had come slightly loose and the barrel had moved forward a couple mm and the slugs were "dropping" a bit so the feed was angled, no go. Re-seated the barrel so the rear brass TP was flush with the breach and bingo, no feeding problems. Just an idea.
Click to expand...

Firstly thank you for the tip, my barrel was seated properly. I always make sure of the barrel seating because i pull my barrel to install the huma single shot loader, so much easier than fighting it in place.

Otherwise.... Posts like this make me pull my hair out. No offense to you 2L8, I read this stuff all the time. I say my .217 JSB KO out of a 700mm barrel is 975fps at 145bar reg, and I hear 960fps at 95bar. Really makes me think I missed something in my upgrade, honestly that is why I changed gauges and did the transfer port and pin probe.



I can't even begin to tell you how many times, and in every hobby I've had, I do the exact same thing as you have done with your Impact. I have now coined it the A, B, C, buying tactic. I start out wanting gun "A". Then after learning a little bit, and wanting more, I buy gun "B". Gun "B" will last just long enough for me to find out what is really going on. Then, you got it, I buy gun "C". Usually the price of gun A, and B covers most of the price of gun C.

I would love to tell you that I have learned my lesson, but unfortunately, I seem to be a very slow learner, and part dumb ass! The collection still grows! LOL What can I say?

I hope you catch yourself "learning your A,B,C's"

Eamon
Click to expand...


Eamon, I hear ya. I thought I learned my lesson with my various benjamin/hatsan/gamo purchases of the past. I once sat down and did the math of all my previous air rifles and bb guns. I could buy every gun I have ever bought again for the cost of 1 Impact.. and if I stayed away from PCPs entirely id probably have $5k in my pocket. Talk about preaching to the choir , I bet that is almost everyone's experience . If I were to do it all over again, Id probably not buy the benjamin armada, or the hatsan torpedo otherwise no regrets.



If the path to success was easy we would have nothing to talk about......
 
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Hunter82

Are you still running the stock hammer spring adjustment slider from your X model, or did you replace it with the new spec Mark ll slider?

I did basically the same upgrades as you did to my X model, and until I modded that adjustment slider from 18mm down to 16mm, I was leaving power laying on the table.

I am shooting the 22 JSB Redesigned Monsters at 960 on a 115 bar reg setting.
 
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Hunter82

Are you still running the stock hammer spring adjustment slider from your X model, or did you replace it with the new spec Mark ll slider?

I did basically the same upgrades as you did to my X model, and until I modded that adjustment slider from 18mm down to 16mm, I was leaving power laying on the table.

I am shooting the 22 JSB Redesigned Monsters at 960 on a 115 bar reg setting.
Click to expand...

I have not done that yet. i was under the impression that high hammer preload at lower reg pressures would beat on the valve. Ill take the last bit of slack out of my power wheel, see what that does.
 
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You can adjust the hammer spring tension until you get a 15mm or .590 gap measured on your slider. That is the max you will get out of it until you mod the adjuster or purchase the shorter version. You can adjust the new shorter slider down to the same 15mm measurement, which will gain you an extra 2mm of preload on the hammer spring leading to higher valve lift and longer dwell.



I do not think that you can get to the point where you are beating on the valve due to the design of the valve rod and how it is buffered at the front with the valve adjuster. Of course I could be wrong about that, so proceed with what you are comfortable with.
 
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Hunter82 said:
Otherwise.... Posts like this make me pull my hair out. No offense to you 2L8, I read this stuff all the time. I say my .217 JSB KO out of a 700mm barrel is 975fps at 145bar reg, and I hear 960fps at 95bar. Really makes me think I missed something in my upgrade, honestly that is why I changed gauges and did the transfer port and pin probe.
Click to expand...
Well, today I measured similar values like 2L8. My Mk2 700 mm barrel sends .217 JSB KOs at 985 fps, reg pressure set to 115 bar.
My Mk2 is equipped with heavy liner, HUMA high flow V2 dual hole transfer port and FX slug power kit.

1690902661679.png
 
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