Setting up the regulator & hammer spring tension correctly is a simple but tedious process, but done correctly yields great results. Something to remember is that you want your regulator set at the lowest possible pressure that will achieve the velocity you seek, so as to give you the most shots and the least wear and tear on your rifle...you don't want to run your gun at the ragged edge of its performance capability.
For example, let's say you want to shoot 34 grain pellets at 800 ft/s... which yields 48 ft/lbs energy at the muzzle. Let's say you start out by setting your regulator at 120 Bar...then the next step is to set your hammer spring tension. My advice is to back the hammer spring retaining nut all the way out, and then screw it back in until it just catches the first threads, then make a reference mark at the top of it at the 12:00 position. Then screw it in using the mark to count your turns to say 6 turns in...then shoot a few shots over your chrony to see what the pellets velocity is. Then turn it in a half turn so it is at 6 1/2 turns in and shoot a few shots over the chony...then to 7 turns in...then to 7 1/2 turns in...etc. As you turn the hammer spring adjustment nut in and shoot over the chrony you will see the velocity increase. You will keep turning it in until you get to the point where the velocity begins to fall back lower, and that is when you back it off until you find the "peak" setting where even 1/4 turn in more will cause it to decrease. This then is the optimum hammer spring tension for that particular regulator setting.
So now let us say you did all of the above and your peak velocity turned out to be 750 ft/s, which is lower than you wanted. So then you would set your reg pressure up to 130 Bar and repeat the hammer spring tension adjustment procedure until once again you reach the peak of adjustment and determine if the velocity is where you want it to be. Setting the regulator pressure up 10 Bar results in about a 30 ft/s increase in the pellet velocity, providing you adjust the hammer spring tension to its peak setting.
To confirm the regulator setting, simply fill the air tank on your gun up to say 150 Bar and shoot pellets over the chrony until it eventually falls below the reg pressure as shown on the rifle's air gauge. You will know when this happens because lets say all your pellets are shooting close to 800 ft/s and all of a sudden a shot will show on the chrony at 780 ft/s...and the next one will show at 745 ft/s for example. If you have your regulator pressure set too high and the hammer spring tension set incorrectly, you will actually see your pellets velocity go up higher when it falls below the regulated pressure as shown on the air gauge, instead of the velocity going lower.
As I said before, it isn't very complicated but it is somewhat tedious. For those of us who appreciate the best accuracy and performance from our rifles this is a labor of love and is a pleasure to do. I do caution you not to rely too much on what others may say the "best" regulator setting is for a particular pellet from a certain rifle...because you will find a great disparity of settings from one gun to another. One gun may have a real high reg pressure setting with the hammer spring nut adjusted only 5 turns in, while another gun has the regulator properly set lower but with the hammer spring nut adjusted 8 turns in.
An example of the disparity in settings would be my Streamline .25 that has a Huma reg in it set at 120 Bar, and shoots the 34 gr. pellets at 825 ft/s average...whereas my Wildcat .25 has the same type of Huma reg in it set to 140 Bar, and shoots the 34 gr. pellets at an average of 800 ft/s. Both rifles have the hammer spring tension set at the perfect peak of adjustment and yet there is a 20 Bar difference in their regulator settings. Is there a difference in the regs? Is there a difference in the pressure gauges from one rifle to the other? I surely don't know! What I do know is that my Streamline originally got about 30 shots and now gets 51...and my Wildcat originally got 40 shots and now gets 64. And the best news is that I no longer have regulators that creep up & down every time I turn around, and I get an extreme spread of around 6 ft/s now.
To me this is the foundation for accuracy to which I add cleaning my pellets with Acetone and lubing them with Napier Pellet Lube, and using a Huggett suppressor which also acts as an air stripper, and drilling small holes in my shroud tubes to vent the blast of air diverted backwards, and set my triggers to about 4 ounces, etc. This is how I get 5 shots exactly in the first hole at 50 yards. I hope any of this helps someone out there who may be struggling to understand how to set up their rifle. And for heaven's sake if you have an unregulated rifle find a way to regulate it!
Best regards, Chuck
As a footnote I want to make one last comment regarding accuracy, and that's the fact that even though I can put 4-5 shots in a row into exactly the same hole at 50 yards with either one of my FX rifles I have several friends who cannot. The best one of my friends can do is 1" to 2" groups, and my other two shooting friends can't do any better than 1" groups with my rifles. My point is that regardless of how well the rifle will shoot, you still need to learn the right way to use the trigger, and how to control your breathing, etc. And above all you have to practice...A LOT! And as you practice a lot you will have moments of sheer joy when you realize you just figured out some new little trick to shooting better. This is what makes shooting FUN for me.
