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PostPosted: Sat Jul 05, 2014 5:01 pm 
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Location: Central West River Nova Scotia
I was tuning my at44 reg recently and relied heavily on airgun regulators chanel on you tube. What I have concluded is it is almost impossible to attain perfection in efficiency, because of all the varriables that have to work together but have seperate varriables each. Just as an example . The barrel length is a varriable , the twist rate of the barrel is a varriable, the size of the transfer port, the hammer weight, the hammer spring, the valve spring, the pressure setting, the pellet type, size, weight, brand, and probably a few more I cant think of right now. So getting every one of the varriables working together would require having a supply of barrels and hammers and springs and tp's and trying each one in unison with each other. Numerous ammounts of pellets and time and air. Mathematics can help a lot if you know which measurements and what numbers are optimal for performance.If you happen to be on of those people who seeks perfection, I advise you not to undertake the task of finding the perfect combination of varriables for the perfect , efficient , pellet gun. Instead, just have fun shooting.

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PostPosted: Sat Jul 05, 2014 7:30 pm 
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Location: Nova Scotia
But Joe, don't you think it is worth it when you finally achieve a fairly flat pellet string? You also left out temperature and humidity which seem to have an affect on pellets, ever notice the puff of vapour condensation when you shoot.


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PostPosted: Sat Jul 05, 2014 8:00 pm 
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I think there are worse fates then your journey becoming the goal.
One step at a time..


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PostPosted: Sat Jul 05, 2014 8:39 pm 
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Location: Coalmont BC
I understand that trying to get a regulated PCP running well can be frustrating, but in fact it's somewhat more straightforward than an unregulated one.... Assuming you don't want to start trying every conceivable combination of pellet, barrel, transfer port, twist rate, hammer, hammer spring, etc.etc.etc.... which you are very unlikely to do on an unregulated PCP.... you are left with really only two major variables, the setpoint pressure and the hammer spring preload.... This is much like the major variables in an unregulated PCP, where the major variables are the fill and refill pressure and the hammer strike.... the combination of which gives you the "sweet spot" for the gun....

Assuming you are installing a regulator in a previously unregulated PCP, you will already have sorted out many of the variables, such as finding a pellet that shoots well in that barrel, and finding out how much power the gun delivers at various pressures.... Then you have to make an intelligent decision about how much power you want once regulated, and decide on a regulator setpoint that has a decent chance of delivering that.... Usually that will be maybe 100 psi more than where your unregulated gun made the FPE you wanted, at the low pressure end of the shot string.... For example, if your gun shot 20 FPE when full (say 2000 psi), peaked at 22 FPE (at say 1600 psi), and dropped to 20 FPE again at say 1200 psi.... and you want 20 FPE, you would choose about 1300 psi for your setpoint, and when installing the regulator, try and leave about 20 cc (1 cc per FPE) as a plenum (pre-chamber) between the regulator and the valve seat.... This gives you a basic setup, and now you are left with playing with the hammer spring preload to make the gun efficient.... This is where most guys have a problem....

If they don't change the hammer spring preload from the unregulated gun, they are likely to be pretty close to their intended FPE level, but get a dismal shot count.... That is because the hammer strike is strong enough to produce their 20 FPE goal at wayyyyyyyyyy higher pressure, so the valve is staying open too long, and blasting air out the barrel after Elvis has left the building.... Fortunately, if you understand that, it's pretty easy to find the optimum preload by shooting only 1 or 2 fills.... Don't change anything, and shoot 2-3 shots and record the average fps.... Back off the hammer spring preload a turn, and repeat.... Keep doing that until the velocity starts to decline, and go a couple more settings beyond that.... Then take a piece of graph paper and graph the results like this....

Image

For almost every unregulated gun converted to regulated, you will be starting up on the "plateau" on the left on that graph, and reducing the hammer spring preload will save air with every turn, but initially you will lose little or no velocity.... Then suddenly, the velocity will start to drop a bit, and a turn or two later it will be dropping a lot with every turn, as you will be on the "downslope" on the right side of that graph.... Where those two straight lines meet, on what I call the "knee" of the curve, is where you want to tune the gun.... 4-5 turns out in this example.... You will be giving up 2-3% in fps yet using about half the air per shot you were when the hammer was tuned to work at 2000 psi....

Once you get used to tuning a regulated gun, you will be able to recognize where you are on the curve just by the way the gun behaves.... If you are on the plateau, the gun is loud, uses a ton of air per shot, and when it reaches the setpoint the velocity plummets with every additional shot.... It may even exhibit a slight downtrend in velocity from full to the setpoint due to slight pressure creep in the regulator.... As you approach the knee, the gun will start to get quieter and use less air.... When it's just right, the velocity will be very stable from full to 100-200 psi BELOW the setpoint and then start to drop gradually.... That's the tune you want.... When you are on the downslope, the gun will be very quiet (and efficient), have noticeably less power, and when you hit the setpoint the velocity will start to INCREASE and the gun get a bit louder, just like an unregulated PCP does as it goes over the peak of the sweet spot.... and that's exactly what is happening.... It may also show a slight upward trend in velocity between full and the setpoint pressure, due to regulator creep.... before the big rise in velocity....

It's all a matter of understanding what is happening inside the gun after you install the regulator.... and realizing that you have to back off the hammer strike to retune the gun for its now much lower operating pressure.... It's not rocket science, and it doesn't need to take up tins of pellets, or tons of air, to find a very efficient tune.... Of course if you guessed wrong on the setpoint and you need more power (or less), then you have to increase (or decrease) the setpoint and start all over again.... Fortunately, you can hone in on your new "best" tune within about 20 shots or so, and by the end of the second fill you should have it dialed right in....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
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Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sun Jul 06, 2014 10:28 am 
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Location: Central West River Nova Scotia
I was talking about the PERFECT BALANCE OF ALL FACTORS. Sure a dacent tune once, as you said, you understand whats happening inside your regulated gun, is fairly easy. But theres always more fine tuning that can be done to improve efficiency. You Bob, seem to have a penchant for math, so getting close to perfection for you, is a lot easier, because you can figure out before hand what you "should" get, instead of trying some thing then testing to see what you did get, and then making changes and testing again, which is the way I procede.
How ever frustrating it might be searching for the best combination at times, I totally love every minute of the journey.
For those of you regulated gun owners out there, who wish to persue a better efficiency, Robert lanes videos are indispensable. Even if you aren't, they are interesting to watch.

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PostPosted: Sun Jul 06, 2014 11:37 am 
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I would still suggest that taking the same journey (trying all the variables) with an unregulated PCP is even MORE difficult....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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