Tuning Yes, another MK2 Tuning Question

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CoyoteGod

CoyoteGod

Member
Mar 25, 2021
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Hesperia, San Bernardino County, CA, United States
I bought a SPAW power tuned MK2 Compact 30 CAL. The tune was doing 925 at 165reg and two Lines out on hammer spring with 44.5 hybrids. It was doing 100 yard groups really well and had a 23 shot count on the bottle. This was of course at a different elevation, humidity, temp, etc. 

Now that I have it I was expecting differences but I am surprised at how different. I am shooting 901-903 FPS for first 5 shots. drops down to 899-897 next 5 shots, then I have a steady drop in velocity from 11-21 shots count. At 21 I am all the way down to 860 and I start to get all over the target and the POI drops. I haven't changed the original tune.

Spread is 45 FPS over 21 shots and deviation is 11. I should be doing better than this right? I know the bottle is small and I wasn't expecting a miracle, but this much of a difference from Florida to California without changing one setting?

Do I basically need to start over with the tuning process?




 
Something happened during shipment. Trust me, it’s happened to me with a guys gun I worked on. If it was shipped fully filled with air, you don’t know where this gun has sat while in route. Air expands when heated, and in my case the owner of the gun came back to tell me after someone else looked at it that it was a stuck valve, or a sticking valve. That will cause erratic velocities, and most certainly a drop in velocity. Fast forward to now, and on my own wildcats I’m experiencing the same. I put my two WC away fully filled with air, and after 10 weeks I pulled them out. It’s gotten a lot warmer in those 10 weeks, and shooting thru the chronograph I experienced a velocity loss, erratic velocities, and a leak that my gun had never had before(stored at 250 bar, 10 weeks later at 190 bar).
 
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Well it appears that my impact is not working correctly if I am getting all of your drifts. I don't have the technical knowledge to take the gun apart and adjust the C1.I guess I have to just hope it's not that. The PW is sometime I can figure out. As far as a stuck valve, same scenario as the C1. I don't have a bottle tether, but I can keep the bottle fairly full as I go through the trouble shoot process. I was really hoping to have it show up and just have fun with it at the SPAW tune. 
 
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If you don’t have the skill to investigate the C1 or the valve, you shouldn’t have bought an Impact. Or any other semi complicated PCP for that matter. All PCP’s require you to perform surgery at some point. These things aren’t set it and forget it like a firearm. You’re gonna have to go for it or you might be on a first name basis with a shipping company.
 
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If you average 902 ("901-903") for the first 5, and average 898 ("899-897") for the next five, that's only 4 FPS difference on the first 10 shots. And that's considering there is no margin of error in your chronograph, if you are using the same chrono as before. It sounds like at 23 shots your compact Impact is falling off the reg. Maybe you will only get 20 good shots.
 
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Well it appears that my impact is not working correctly if I am getting all of your drifts. I don't have the technical knowledge to take the gun apart and adjust the C1.I guess I have to just hope it's not that. The PW is sometime I can figure out. As far as a stuck valve, same scenario as the C1. I don't have a bottle tether, but I can keep the bottle fairly full as I go through the trouble shoot process. I was really hoping to have it show up and just have fun with it at the SPAW tune.
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Give us a call at FX USA. We can walk you through checking the C1. 866-639-0772 option 1.
 
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If you don’t have the skill to investigate the C1 or the valve, you shouldn’t have bought an Impact. Or any other semi complicated PCP for that matter. All PCP’s require you to perform surgery at some point. These things aren’t set it and forget it like a firearm. You’re gonna have to go for it or you might be on a first name basis with a shipping company.
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Thanks for the reply and straightforwardness. Yes I am going to just go for it, I will check the C1 and record the current tune and retune and see if I can get a full mag shot string that will group well at 100. I will also call SPAW. Thanks for the reply. 
 
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Started following all of your advice. First call was to Ken Hicks. Felt like he would spend all day with me. Great guy. He looked up the rifle for me and saw everything he did in real time with me. He said this rifle was purpose built to be a hot rod slugger for hunting and if benched, tethered to a bottle. He normally doesn't make compacts this hot, but it was for Dr. Mike Long's PTSD Veteran' Shoots in Washington so it was made for this event and after for hunting. He built the rifle just this April. He said this gun is basically maxed out while still being accurate.

So I explained every issue (I thought I was having). He said 905-896 for 10 shots at this power level on a compact is pretty good. He said the rifle is pretty consistent to 17 is normal with the tune the gun has. He said it will definitely shoot different from Florida to California and a 25 FPS difference on my Chrono vs his is nothing to worry about. He guaranteed that the C1 was fine and there is no need for me to worry about it, as he "locktite's the hell out of them". He had me check the power wheel, which it was fine. We checked the hammer spring adjustment and the reg pressure at 165. So the rifle is still at his tune. He said there is noting wrong with a 15 shot count hunting rifle on a compact and sounds about right for this rifle with this tune. He said "you bought a hot rod and you are not going to pass up any gas stations". He said I can do some slight movements and get a little more out of the rifle, but if anything I should detune it if I am doing anything other than just hunting. He told me to pass on a 480CC bottle and just keep filling. he said 15 shots in the field walking around is a full day for most folks. 

I did buy this to hunt with, not target shot with. Ken told me how to power it down for pellets for the backyard to play with if I desire. He asked me to do 10 shot groups at 50 and 100 this week and call him back and see how it was grouping. Only 10 shots a time and refill between shots and we would go over the results, which was really nice of him.

He said I would be fine dropping the power wheel to 5 or 4 and dropping 10-20-30 FPS and get 4 or 5 more shots on the bottle. Also he said he would help me retune if I wanted to shoot lighter slugs or move to pellets, which would most likely get me to a full magazine shot count or more on the 300CC bottle.

According to Ken, just enjoy the hot rod and have lots of air on hand. 
 
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That all sounds good to me. I should have paid more attention to your 165 bar set point and considered the compact bottle before replying. Once you hit the set point, or very close to it (gauges aren't precise) you are off the reg and all will go downhill from there.
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Ditto for me. I should have seen what Jayson obviously saw and mimicked his reply. You’re asking a lot out of that tiny tank and short barrel. 
 
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According to Ken, just enjoy the hot rod and have lots of air on hand.
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That Ken is a real pip!





On the level though, if Ken says you are good, then it's pretty safe to bet that everything is OK.
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Ken was super nice, he set me at ease. He basically said enjoy the 17 shots of power and get to it. lol
 
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I was able to get out an do more testing on the MK2 30 CAL Compact. I shot 44.5 hybrids and FX pellets 44.8. Tested superior liner and heavy liner.

All shots were at 45 yards. This is as far as my yard can do safely. Had a little bit of wind, but didn't really affect accuracy. So what I figured out right away is I have 17 shots with both slugs and pellets before it falls off regular. The rifle is super hot but super consistent to 17 shots.

*FX Hybrid slugs 44.5 superior liner - Average of 903FPS, Spread 8FPS,. Deviation 2FPS, average FPE 80.39. Groups were a ragged one hole with my shooting ability. Shot 10 shot groups and the hole was about 1 inch, give or take a few centimeters. I had a few first shot fliers after refill to 250BAR but I just discounted that. This slug is what my rifle is zeroed to shoot. 

Interesting fact, changed to superior heavy liner and shot 17 rounds. About the same in all categories, however the POI shifted 4 inches higher at 45 yards. I was shocked. Changed back to superior liner and POI was back to normal. Was not expecting that.

*FX Pellets 44.8 superior liner - Average of 908FPS, Spread 11FPS, Deviation 3FPS, Average FPE 82.83. The groups were fantastic, slightly better than the slugs, but I was shooting at only 45 yards. I know the slugs like to have a little longer distance to stabilize. POI was of course way off. They hit low and left about 2 inches, but were one hold groups. Wish the slugs and pellets shot the same POI. 

I have plenty of air to deal with the 17 shot count (bottles and a compressor). I think I am willing to let the rifle be hot and deal with any issues of wear and tear that might come up instead of tuning it down and starting over. Like VetMX said, get to know your rifle if it stops being what it was. Honestly when I am comfortable and the scope is doped to 150 on paper I will only use this for hunting so I won't shot 100s of rounds a month, unless I can get to Florida for iguana! 

Just sharing my experience. I have never had such a consistent rifle before. I have some Nielson 43.8 coming to play with in about a week. I bet they will shoot great too (hoping). I wanted to try the 47.5 also but I will wait and see how the 43.8 will do. 


 
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Thanks for the post, following! I haven't tried any slugs that I can remember in my .30 setup (700mm 580cc), so it's good to see how others are fairing with slugs. I know the JSB 44.75s probably can't be beat for groups with the STX liner. That setup has yielded 10 gray squirrels with all headshots at 62 yards and 15 at 85 yards with all headshots but two. Plus three coons so far this year, but only at 25 yards on the coons digging up my garden and yard. I do have the Slug A liner, but it does not do as well with the JSBs. I do also cast my own pellets for the .30 cal so ammo around the house is endless as I reclaim the lead from a rubber mulch bin and recast them.

I also have a .25 cal setup (600mm), which I'll be switching over to here soon since hunting season is over and I'll just be plinking around the house and maintaining the homestead with less range. I also drop the power back for more shots, sometimes. I cast pellets and slugs for the .25. I have the STX and the STX Superior for the .25. Gotta keep the shooting skills up.
 
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