Im curious, when they say you know when the gun sounds right, what exactly are you listening for and what is it suppose to sound?
Tuning Fx impact mkii .25 tuning help
- Thread starter california.airgun
- Start date
Describing a sound it words is more than difficult unless you have heard it. Ted has a tuning video from several years back that has the information you are after. It also has a recording of the sound you are after. It should help you on your way into the depths of the addiction a little further if that is your desire. ;^) The recording of the sound is at around the 9:10 minute area.
https://www.airgun101.com/component/allvideoshare/video/how-i-tune-fx-impact-and-crown?Itemid=362
https://www.airgun101.com/component/allvideoshare/video/how-i-tune-fx-impact-and-crown?Itemid=362
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A crisp shot sound is what you're looking for not a bonng. More like a pthhp.
Haha typing sounds is fun, you should be able to tell when the gun is efficient and happy.
Haha typing sounds is fun, you should be able to tell when the gun is efficient and happy.
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No shortcuts. Lots of trigger time and tuning and you won’t have to ask this question. Your gun even has a cheater knob to attain this. If you haven’t heard the change in sound while adjusting your gun, you are in too much of a hurry to sling lead. Pay attention to your gun, you will hear it. Think, is my gun blasting air or is it sipping air. The sound at the muzzle doesn’t lie. Hanging a giant can on the end of your barrel doesn’t help. A perfectly tuned gun can get away with a smaller can than the same gun that’s wasting air. The little Donny that came with my .25 Impact is plenty quiet when the gun is tuned perfectly but it lets me know when I’m wasting air at the start of a tune.
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Airgun 101 - PCP Air Rifle Tuning Demonstration (the secret is in the sound)
I can barely hear the difference, but it's there
I can barely hear the difference, but it's there
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All good info above. One quick way to tell if you are wasting air (louder report) from being out of balance between the hammer spring, valve knob and reg set point is to lower the power wheel a click or two to see if the report gets quieter without losing velocity. If so, this will indicate that the hammer spring was set too stiff/high. Also, when you are able to shoot below the reg set point a good ten shots or more without losing velocity, you then know that you have a well balanced tune set just below the knee of the desired velocity. With this, the gun will be the quietest it's going to be regardless of the desired velocity you are tuning for with a particular projectile weight.
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I'm not trying to thread highjack, but I didn't want to start a new thread with the same subject. I have the 25 impact compact (500mm barrel) with a power plenum, slug kit, and dual transfer port. I have the 25-grain kings shooting at 980 on max and 917ish on min. I'm essentially tuning for hybrid slugs and lower weight NSA slugs with pellets to get me into the speed ballpark, so I don't have to waste too many slugs. I have made adjustments to the reg (roughly 135 bar), hammer spring preload to where adjusting it down brings the pellet speed down, and micro-adjustments on the valve. I'm a little over line two with the stock spring in the valve adjuster, not the slug kit spring. My issue is my extreme spread. For some reason, the rifle will shoot in the 980s for a couple of shots, then I'll get spikes in speed up to 1000 and lows down to 970, on max. I let the rifle sit with tape on the reg overnight, and it's staying consistent with no creep. I feel the hammer and reg are good as I reduce the hammer, there is a reduction in speed, and when I make a micro-adjustment with the valve inward, my speed drops and vice versa. My current setup is at the point where any little adjustment makes a difference, which is good, I would think, meaning I'm not overdriving the valve with too much hammer, not wasting air, etc. How can I reduce my extreme spread? Maybe it's the ammo as I'm not sorting ammo, and I am lubing the pellets with a light coating of Slick 50 one Teflon spray. I want to make sure that I'm not missing something adjustment wise on the rifle before I transition to tuning with slugs. My theory with the tune is a short burst of high pressure to make sure that the valve closes before the projectile reaches the end of the short barrel.
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Quit lubing your pellets with Slick 50. It’s not necessarily and you are adding another variable. Another thing that concerns me is why aren’t you using the spring from the power kit? Did you read somewhere not to use it? Consistency comes from a balanced system so by you leaving out part of the system, could be a problem.
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Here is also something else to think about. I have a .25 Impact PP with a 600mm barrel. With absolutely no mods to the gun, my base tune is exactly like yours. I shoot 25gr pellets around 980fps after backing off the HS a little and turning in the VLA. But I do all this at 115b and the gun is very efficient. So you have to ask yourself, are you over driving the gun chasing speed.
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It could very well just be some undersized heads in the mix or some lighter loads. But, with lubing the pellets that's not as likely as the lube helps some overall. I get the best consistency when using lubes (silicon). I have my valve set to just a hair pass the first line edge using the slug kit for best consistency. Tuning with the slug kit is a little different when seeking consistency and the dwell knob needs to be dialed in more for consistency. Just make sure you tune ~5% higher in velocity than your target goal and use the valve knob to drop the velocity by the 5% back to your target velocity for best consistency.
The slug kit HS is just slightly shorter than the original to allow for the two additional spacer weights is all. If the valve rod is smooth and not scared or bent and the hammer bumper is good, that should be good there. Also, make sure the valve rod cap hasn't come loose on you and measures no more than 5.5mm or 6.5mm (memory block may need to look that up) from the action block.
The slug kit HS is just slightly shorter than the original to allow for the two additional spacer weights is all. If the valve rod is smooth and not scared or bent and the hammer bumper is good, that should be good there. Also, make sure the valve rod cap hasn't come loose on you and measures no more than 5.5mm or 6.5mm (memory block may need to look that up) from the action block.
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I wasn't using the slug valve spring based on how much more substantially stiff the stock valve spring is than the slug valve spring, which feels slightly on the weaker side, making sense seeing how it allows the valve to remain open longer. I was using the stock spring, which is the theory, being a stronger/stiffer spring, should provide the same amount, if not more, adjustability range as the slug spring without having to turn the valve in as far, but even with the stock stiff spring, it's turned in to almost line 2. Hell, I have to completely close the valve to get air to seal once I release pressure from the system. I can try with the slug spring when I get home. I have a 600mm slug liner on my bench, just waiting for parts from FX to complete the barrel build. Not chasing speed perse, trying to find a happy place where I can put the rifle on max and shoot slugs with the 600mm heavy liner and put it on min, throw the 500mm barrel on and shoot pellets.
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I would agree that I like using lube as a bit of the lube rubs on the breach o-ring making the probe fit and seal smoother. I didn't get an HS with my slug kit, mine came with a spring that I would use on the valve adjustment side. I just watched the Airbuks slug power kit install again and it shows him removing the stock valve spring and replacing with the less stiff slug valve spring. Before I tore it all apart, I measured the cap extension to about 6.2-6.5mm and marked the rod before removing so I should be good there but I can measure it again when I get home.
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The shorter valve spring comes with the PP kit, or with a PP equipped model I would assume. Also, a new brass HS spring guide to replace the original plastic guide. That's strange about your ES spiking. For a while I was running a hybrid setup using the long original valve spring inside the new PP that was being used in the non PP MKII. Plus of course the rubber ball valve cap with that, and the original HS. I had excellent ES results with that setup. The slug kit includes the two additional spacer weights and new valve spring and valve cap, or maybe I have them mix up a bit. It has been a while. I am currently setup with the full kits now as designed using the new, shorter HS and both spacers along with the new valve spring and cap. I am still getting a very tight ES, but maybe not quite as tight as the hybrid or pre PP kit. Do you have a PP? And if so, how are you preventing the old valve spring inside the PP from dropping into the air inlet of the PP?
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Ok, so there are only two springs that I know about in the system based on the breakout above. We might be using terms that are not meshing with each other, so I'll refer to them as the part number. I have the newest MKII Power Plenum. When I initially broke the rifle down, I noticed that it didn't even come with a rubber ball as the previous-gen did. I called service, and they said it is no longer included with rifles built with the power plenum (pictured above). So, when my slug kit came in, which I don't believe was old stock as I had to wait on pre-order to get one a few weeks ago, it only came with one spring and the rubber ball, which replaces C42 on the top drawing. My kit didn't have a replacement for the spring C7. I did put the spacers on C6 and adjusted the C1 back to its proper place. There were no other modifications I made to this area. When you say old valve spring inside the Power Plenum from dropping into the air inlet of the PP, what do you mean by dropping into the air inlet? I've seen a spring there on the older non-power plenum and MKII models like the one below but mine doesn't have a spring inside the power plenum like the old C42 in the below picture:
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Right, so no need to concern yourself with the older parts, like the old valve spring in the plenum C42. It sounds like you have all of the latest upgrade offerings from FX for your MKII. It's hard to keep up as some MKIIs didn't come with power plenums, like mine. The rubber ball gets placed inside the valve spring that is placed over C1 as a safety check valve, just incase something went awry with the valve seating to prevent a full dump of the tank. C3 is now incorporated into the tip of C5 for better durability. As a side note, Earnest Rowe has just come out this week with a C1 removal tool that will make removing/installing the C1 much easier.
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Ok sounds good. I'll try replacing C42 and testing again to see if I'm still getting a wide ES, but I honestly can't imagine having the stiffer stock spring in there would cause the issue. I would think that putting in the lower power C42 spring will just mean that I will be screwing the valve down to just outside line 1 instead of line 2 but that's theory and it's worth a shot, literally. I'll also recheck the C1, I do recall that after putting on the spacers, I had to screw the C1 a bit further on so I might be outside to range still by a little bit. It was 6 to 6.5 mm right?
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FX mentioned producing a slug kit tuning video a while back, but nothing I have seen yet. I am running my 600mm at 70 FPE with 37gr weights with reg set at 125 bar. If you are not running heavy weights at high speeds, maybe the slug valve spring isn't for you, or the extra hammer weight spacers. All of which are harder to control the ES with unless tuned well, I do see 3 to 4 duplicates in a row run across the chrono at times, but my projectiles are weight sorted down to a 10th of a grain and are all sized to 0.251" and lightly lubed. with using the STX or the STX Superior liners.
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