Tuning Novice trying to tune .22 Dreamline Tac Compact bottle

[Vetmx]

Not meaning to hijack this topic but it did inspire me to do a full shot string with my gun. I knew I was at about 6.5% below my max velocity but I left it that way because from time to time I will experiment with slugs or the JSB 25gr .22 pellet. I needed room to jack up the speed considerably while testing. The string definitely confirmed I was operating on the downslope because I had a rise in velocity before it came off the reg. I dropped the reg and worked my way up to 920fps on Max. I set the wheel to #5 and it was still too fast. But #4 was too slow. I wound up putting it back on #5 and backed it down to the 890’s with a hex wrench. What’s interesting is my HS wheel was much more linear controlling my speed at the slightly higher reg setting. At my new reg setting, the FPS drop between #5 and #4 is significant. I agree with qball, when you get your gun in sync, it’s a noticeable change. Whether tuning upwards until you feel it get crazy or tuning backwards until you feel it calm down. With my Leshiy it’s really noticeable. Good luck and follow what qball and jasmlowe recommended. Our DL Compacts are just a little different and I was giving bad advice.

 

[TN_Yankee]

Alright, I got a little time today to throw some 15.89 lead over the chrono. At 110b, PW max & TP medium, I couldn't really get past 800fps. I bumped it up to 120b, PW max, and got 820 on TP medium, 835 on TP high. I went back to TP medium and played with the power wheel. PW4 gave me 790, PW3 gave me 725, so I went back to 4 (since it was closer to the 760 goal) and dialed the HS screw down a tad. I ended around 765 on PW4, TP medium. I quickly zeroed it at 20 yards and called it a day. FWIW, the hammer spring adjuster gap is 18.1mm, so it's quite a way from being max'd out.

I have more testing to do, but assuming the speeds stay where I left them today, I won't be touching the regulator or HS screw. I want to do some accuracy & speed testing with the Hades & 18g pellets, as well as the CPHP & domed. I getting low on air, so won't be running a full string over the chrono any time soon, but I definitely want to do it.

Thanks for your help, gentlemen, and hopefully this will get me on the right path moving forward. Now to get a compressor...

 

[qball]

@tn_yankee: nice!!! It’s actually really easy once you find the range. If your gun is at 120 Bars and 16 grain is at 760 FPS on HS4 then the 18 grain is very likely to shoot around 760FPS with HS of 5 and CPHP would likely to shoot in the same speed at HS of 1 or 2. All three can have the same speed range and same POI at 20 yard zero, so with a twist of dial you can shoot 3 different ammo without changing anything else. If you get bored you certainly could adjust the HS preload a little at a time to push the speed up a little but listen for the tone change in muzzle blast, the reason I suggest 760fps target is because it’s in the safe range where you will get very good results without a lot of time fine tuning at the edge. Practically speaking the extra 20fps you might squeeze out fine tuning doesn’t do anything even down range besides very slight drop decrease. But keep in mind that lighter pellets will be less accurate/consistent if there are more muzzle blast. 


BTW the CPHP is freakishly accurate even out to 100 yards out of the superior liners if condition permits, they have Low BC. Under 60 yards they are crazy good for under 2 cents a pop! They are so good I haven’t bought JSB pellets besides a few tins of hades in over a year. 


Also I found CPHP to have noticeable increase in consistency with a little bit of lube/pledge(not wash). I found no need to wash CPHP at all, just lube with paper towel using Tom’s method in the video.







https://youtu.be/b_9fP1z8D08

 

[Vetmx]

Something is perplexing me so maybe qball can help me understand why you guys are tuning the gun with the TP set on medium. If TN is content with starting his tune at 820fps at 120b with the TP on medium, why wouldn’t he back the reg down to 110-112b and set the TP on high. His gun showed a 15fps increase when he increased the flow. Just curious because I don’t choke off any of my regulated PCP’s unless I want to quickly go to a much lighter pellet. 

 

[TN_Yankee]

why wouldn’t he back the reg down to 110-112b and set the TP on high.

This question had occurred to me later, too. I had limited time available yesterday, so I was focused on following @qball's specific advice.

 

[qball]

Something is perplexing me so maybe qball can help me understand why you guys are tuning the gun with the TP set on medium. If TN is content with starting his tune at 820fps at 120b with the TP on medium, why wouldn’t he back the reg down to 110-112b and set the TP on high. His gun showed a 15fps increase when he increased the flow. Just curious because I don’t choke off any of my regulated PCP’s unless I want to quickly go to a much lighter pellet.

Good question, depends on the tune in my experience there is little to no difference for 177 and 22 when using TP between Medium and High. Also in my experience when I put TP on high the lower HS settings actually lose speed. I've opened the TP before a few time the medium TP port is about the same size as .22 bore while the high setting is about size of .30 bore. When not on higher tune I found lost of speed using TP on high because that's extra volume compressed air has to fill before reaching the actual transfer port. This in theory will delay the energy transfer to the pellet by filling the TP chamber first, in a short barrel a very slight delay could mean the valve might not close in time before the pellet leaves the barre. As soon as the pellet leaves the barrel the pressure in the chamber almost immediately drop and if the valve isn't closed you will waste a ton of air, air travels much faster when the pressure delta is much higher between 2 sides of the valve. On my 600mm .22 barrel on my crown I do get about 20fps faster speed if I use TP on high but the barrel is twice as long so a little delay isn't an issue. The 300mm barrel is so short timing the valve to close between the pellet leave the barrel is a lot harder, I found right around 760fps is a comfortable speed almost regardless how you get there. 

IF you get a medium hammer and set reg at 150 bars then TP on high might get you the extra 20fps without worry too much about valve closing too late since there is a lot more force on the valve from the tank air pressure itself. Key is listen to the muzzle blast as you increase speed, as soon as you hear the muzzle blast change tone to louder then just back it off a little. This is from the great Ted Holdover and IMHO one of the best tuning techniques of all time regardless of the endless Reg, TP and HS combination. Listen to your gun! 

 

[qball]

why wouldn’t he back the reg down to 110-112b and set the TP on high.

This question had occurred to me later, too. I had limited time available yesterday, so I was focused on following @qball's specific advice.

The specific instructions are to get you in the ball park of an efficient tune. Once you are familiarized with a good/efficient tune you can start tinker with different settings to push toward the limit/edge a little but without knowing how a good tune suppose to sound and feel like you most likely won't know when you push a little too far. With longer barrels it's no where near as sensitive but the short little 300mm barrel is very sensitive to being over powered and waste air while creates more flyers/degrade accuracy. Keep in mind there isn't a definitive "right way" to tune it, there are endless combination with the 3 possible settings for each ammo at each power level you want to shoot at. It's a lot of fun if you like tinkering but some people don't like to tinker then stick to a conservative/efficient tune is the best way to stay out of frustration. 



A good analogy is a drag race: if you are given 600 feet of pavement to get to 60 mph you will likely say it's not too bad or easy, but if the pavement is cut to 300 feet getting to the same 60MPH then it's not so easy anymore. If you learn how to tune a short barrel airgun well then tuning longer barrel airguns will be piece of cake. 

 

[Vetmx]

So basically you’re choking the gun to control dwell instead of shaving some weight off the hammer and running it wide open. I would like to see a shot string with the gun at 112b wide open and the gun at 120b on medium. With a 820fps max speed and HS backed down to 785-795fps. Then an accuracy comparison. Dirty air might be a deciding factor. This is very interesting but that’s probably why my short barrel is laying on top of my gun safe. I guess to bottom line is if you’re going to have a pistol barrel on a rifle, you should focus on tuning around pistol velocities.

 

[qball]

So basically you’re choking the gun to control dwell instead of shaving some weight off the hammer and running it wide open. I would like to see a shot string with the gun at 112b wide open and the gun at 120b on medium. With a 820fps max speed and HS backed down to 785-795fps. Then an accuracy comparison. Dirty air might be a deciding factor. This is very interesting but that’s probably why my short barrel is laying on top of my gun safe. I guess to bottom line is if you’re going to have a pistol barrel on a rifle, you should focus on tuning around pistol velocities.

100% correct. Only exception would be Edgun L2, reason for that is because of extreme high reg pressure. L1 and L2 main method of increase speed/power is to raise reg to over 200 bars. Being a hammerless valve system it has the ability to control the valve closing a little better compared to traditional hammer and valve. Obviously the disadvantage would be low shot count and loud.


For most normal airguns with traditional hammer and valve setup a given barrel length will have an optimal speed range given the “normal” reg range. 


also going back to the drag race analogy, by cutting the distances to reach 60mph by half the power required would be more than double and at some point even impassible. Same thing in the PB world, you don’t see rifles rounds reaching 3600fps with a 12 inch barrel.