is it better to have a low reg pressure or high if you can shot the same pellet speed.
On a fx impact cal. 22
On a fx impact cal. 22
Fx impact reg pressure
- Thread starter spyde82
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Yes but some say that a higher reg pressure help close the valve and then give a better shot count. 
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I've often wondered that. And I've heard different versions of how to tune from different very good successful tuners. The question is:
- Do you use the lower reg. pressure with a high hammer spring tension or heavier weight, or both.
or
- Do you use a higher reg. pressure with a lower hammer spring tension or weight, or both.
I've heard arguments on both sides that make sense... For the same pellet at the same speed of course.
- Do you use the lower reg. pressure with a high hammer spring tension or heavier weight, or both.
or
- Do you use a higher reg. pressure with a lower hammer spring tension or weight, or both.
I've heard arguments on both sides that make sense... For the same pellet at the same speed of course.
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The gun might be more accurate with a higher reg pressure than necesarry to get the desired speed, and good efficiency. But you have to test for yourself. The impact is a different than other guns, as the valve stop adjuster allows you to experiment with a wide range of reg pressure, and still optain litle velocity variation from shot to shot. I have personally shot in the low 700 fps range, where the max speed of the gun have been 900fps, and still optained an ES within 10-15 fps. You can do that by just lowering the hammer strike, and control the ES with the valvestop. That is like 150 or more fps lower than max speed, and not the most common way to tune most guns. It also depends on what velocity you intend to shoot at. If you intend to shoot at low velocity, the reg might give more stable pressure if you do not lowering it to much (not sure the reg likes to be as low as 80-60 bar). If you intend to shoot at high velocity, the hammer strike might not be able to hit hard enough to get the desired speed, if you go to high on pressure. If you intend to keep the same speed, you can increase reg pressure 5 bar at a time, and adjust the rest of the gun, to see if it gets more accurate.
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I am not an expert tuner, but it is probably easier to pick a velocity range, and adjust hammer tension to find the speed which gives you the best accuracy with different reg pressure. Fine tuning reg in small increments is not that easy, while it is much easier to fine tune speed with hammer tension or valve stop. I do not believe the gun care that much if you shoot 840,860 or 880 fps as long it is accurate.
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Just a brief comment about the relationship between efficiency and shot count. They are related but more of one does not mean more of the other.
The highest efficiency is possible with high pressure. Very short valve dwell uses a very small volume of high pressure air. This high pressure air produces faster acceleration (a kick in the pants…or the skirt as it were), and the smallish volume of air continues to expand and accelerate the pellet all the way to the muzzle.
However, the highest shot count will almost always be at some lower pressure. That’s because there is more overhead available…the difference between the fill pressure and the regulator’s setpoint. For example, a 3000psi fill pressure and a 2200psi regulator setpoint has 800psi of overhead, versus a 2500psi regulator setpoint having only 500psi of overhead. For a given velocity/energy, the former will almost always give a higher shot count but its efficiency will be lower.
The highest efficiency is possible with high pressure. Very short valve dwell uses a very small volume of high pressure air. This high pressure air produces faster acceleration (a kick in the pants…or the skirt as it were), and the smallish volume of air continues to expand and accelerate the pellet all the way to the muzzle.
However, the highest shot count will almost always be at some lower pressure. That’s because there is more overhead available…the difference between the fill pressure and the regulator’s setpoint. For example, a 3000psi fill pressure and a 2200psi regulator setpoint has 800psi of overhead, versus a 2500psi regulator setpoint having only 500psi of overhead. For a given velocity/energy, the former will almost always give a higher shot count but its efficiency will be lower.
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Really good point nervous.
we tend to run high reg pressures but we just turned down an impact for barn shooting. It would not go slow enough with the higher reg pressure and stay accurate. Plus the way that gauges vary, its best to tinker with your own gun. I know thats a horridly unhelpful statement but it is true for sure. Tinker away!
we tend to run high reg pressures but we just turned down an impact for barn shooting. It would not go slow enough with the higher reg pressure and stay accurate. Plus the way that gauges vary, its best to tinker with your own gun. I know thats a horridly unhelpful statement but it is true for sure. Tinker away!
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not necessarily, it is all about a balance between the pressure of the regulator and the tension in the hammer spring, if you have the pressure of the regulator low and the hammer hitting very hard, you will waste a lot of air and your rifle will be inconsistent, the ideal is to achieve a balance.
https://youtu.be/9K9uG2KOPt0
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When I first got into regulated PCPs, I read a lot of random / subjective info on tuning. What I have adopted is a personal belief that every projectile has an "appropriate" reg pressure that should be used to drive them for that platform.
With my Crowns, I started machining hammer weights with the goal of using the minimal weight needed to open the valve at the pressures I needed it to open. I was surprised that the scale of the weight difference required for going from (example) 160 bar to 190 bar was only .6 grams with the ~21 inch/pound factory spring. At one point, I had jumped up 2 full grams from what was needed in gross hammer weight, and it just shot really sloppy.
My point to that is that I found perfect harmony with my reg pressure and hammer system with a custom hammer weight, but I had to build like 8-9 different weights to get there. That perfect match never gives me more than a 3-5fps ES when I tune for 18gr pellets or 28-36gr slugs.
Also, I don't screw around with slamming my hammer into a valve that's holding +20fps's worth of pressure above the target velocity. I tune the pressure aggressively with configurations like what I have in my Crown, and just scale back the spring tension until it's a nice and quiet little psst, with consistent ES.
So for me, it's higher pressure with tiny VDT.
With my Crowns, I started machining hammer weights with the goal of using the minimal weight needed to open the valve at the pressures I needed it to open. I was surprised that the scale of the weight difference required for going from (example) 160 bar to 190 bar was only .6 grams with the ~21 inch/pound factory spring. At one point, I had jumped up 2 full grams from what was needed in gross hammer weight, and it just shot really sloppy.
My point to that is that I found perfect harmony with my reg pressure and hammer system with a custom hammer weight, but I had to build like 8-9 different weights to get there. That perfect match never gives me more than a 3-5fps ES when I tune for 18gr pellets or 28-36gr slugs.
Also, I don't screw around with slamming my hammer into a valve that's holding +20fps's worth of pressure above the target velocity. I tune the pressure aggressively with configurations like what I have in my Crown, and just scale back the spring tension until it's a nice and quiet little psst, with consistent ES.
So for me, it's higher pressure with tiny VDT.
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