Relationship of Air Pressure & Cocking Lever

[Hate The Rain]

Hello from Oregon,

Saw a comment in a post I was reading that stated something like this, "the higher the air pressure, the harder the cocking lever is to use". I hunted a bit and didn't find anything supporting or disproving this statement. And since my logic elevator sometimes doesn't get to the top floor, I thought I would toss this out to the group.

To me, there is no relationship between the pressure of the air in the PCP and the difficulty of operating the cocking lever???? Am I full of #$#%^ or is there any connection between the two? From my limited, and new to the PCP as a way to invest your retirement dollars perspective, there doesn't seem to be a mechanical connection.

Please educate me or please point me to the correct post to get that education.

Thanks

 

[JimD]

You are basically right but when you raise the regulator pressure on a regulated gun you also need to raise the hammer spring force or the velocity won't go up. Increasing the hammer spring force does affect the cocking a little. But there is no direct connection between pressure and cocking.

 

[Hate The Rain]

Thank you. Hadn't thought of increasing the hammer spring as a necessary step, but it does make sense. But that brings up another question, if you don't mind. Why wouldn't it be necessary on a non- regulated gun as well?

Would seem that a pressure increase is a pressure increase and the hammer would need that adjustment on both types of air gun to utilize/take advantage of that increase???

I do appreciate the education and your time.

 

[Ezana4CE]

Thank you. Hadn't thought of increasing the hammer spring as a necessary step, but it does make sense. But that brings up another question, if you don't mind. Why wouldn't it be necessary on a non- regulated gun as well?

Would seem that a pressure increase is a pressure increase and the hammer would need that adjustment on both types of air gun to utilize/take advantage of that increase???

I do appreciate the education and your time.

@Hate The Rain Let’s establish this understanding first - the maximum air pressure recommended by the manufacturer to fill your reservoir is your ceiling in an unregulated PCP airgun. In a regulated PCP the ceiling is dictated by the pressure setting of a fully functional regulator aka “the reg’s set pressure” (“reg” is short for regulator). The set pressure is maintained until the reservoir pressure drops below the reg’s set point.

In an unregulated PCP that is the top of our “sliding scale” of air pressure per shot. If the max pressure in the reservoir requires more force from the hammer one would increase tension in the hammer spring to overcome the pressure on the reservoir side of the valve. Once the shooter presses the trigger, the hammer hits the valve with enough force to overcome the pressure contained within the reservoir releasing air through the valve, to the transfer port, and into the barrel between the pellet probe and the rear of the projectile. This pushes the projectile down the barrel into the rifling and propels it towards your target.
After the shot, the reservoir pressure decreases. On the next shot (and on subsequent shots) the pressurized air in the reservoir continues to decrease, but the hammer still hits the valve just the same. The result is a changing velocity string that affects where your projectile impacts your target even when you do nothing else to change your point of aim (POA).

In a regulated PCP, you still need to heed the manufacturer’s recommendation on max fill pressure, BUT this pressure is not what dictates the ceiling of your shot string. Instead the regulator is set at the desired pressure level that will often be set significantly lower than the reservoir’s maximum fill pressure. There are some advantages to this. The primary advantage is that there is more shot-to-shot consistency because when the regulator functions properly it ensures that very similar amounts of air will be released per shot until the reservoir’s pressure approaches the regulator’s set pressure. With that said, where you set your hammer spring tension to overcome the valve at the reg’s set pressure level should ideally provide the most consistency between shots (we’re talking velocity here) demonstrating efficient use of the compressed high pressure air stored in your reservoir. This is where hammer spring tension correlates to air pressure. To my understanding - the higher the pressure, the heavier the cocking. For me it’s easier to feel on bolt action PCPs, but I’ve experienced feeling more tension on side-lever action PCPs as well.

This is my understanding. My understanding may be flawed and more experienced members will likely correct me where I’m wrong. In the interim I hope it helps you some.

 

[nervoustrig]

Why wouldn't it be necessary on a non- regulated gun as well?

It is. The fundamental effect of elevated pressure is the same whether we are dealing with a regulated PCP or an unregulated one. I think it’s just easier to conceptualize what is going on if we talk about a regulated PCP.

So for example, let’s say I have a regulated PCP set up for shooting paper targets in the basement. I might have the regulator set pretty low at 1000psi.

Later on I decide I want to reconfigure it for smacking ground squirrels, and I crank the regulator up from 1000psi to 2000psi. I know I just made the valve harder to knock open. It’s like I’m trying to push open a door while someone is pushing against it on the other side, and my dainty daughter just stepped aside for a grown man to take her place.

So conceptually it’s really easy for me to grasp that 2000psi is harder to overcome than 1000psi. Number A is bigger than number B.

Whereas with an unregulated PCP the pressure is progressively falling with each shot. However much hammer spring tension I have it set to will give me some kind of velocity bell curve. For some number of shots the velocity will be gradually increasing, until eventually it peaks and then begins tapering off. Just an example:

If I increase the hammer spring tension, I make it harder to cock (at least in some measure), but also two things happen together. The center of the bell curve moves up to a higher pressure, and the peak velocity grows higher. Maybe that’s exactly what I wanted and I’m happy with the result. Or maybe it pushed the useful part of the bell curve out beyond the safe fill pressure for the rifle. That’s about the simplest scenario for which one might adjust hammer spring tension, and hammer spring tension alone, on an unregulated PCP. But often times it will be part of a more meticulous set of adjustments that include things like porting, hammer stroke (travel), etc. Just a deeper rabbit hole to go down.

Comparatively, regulated PCPs are easier to understand and easier to tune... the direct benefit of being somewhat more complicated in their construction.

 

[JimD]

I agree with the other comments on guns without a regulator. An easy way to think about it is the hammer force on an unregulated gun is usually set to handle the maximum fill pressure. On a regulated gun the hammer is mated to the regulator pressure.

 

[Hate The Rain]

Thank you all for taking the time to give an excellent explaination.

I was missing the max fill pressure angle of the unregulated versus the "static" hammer set point of the regulated air gun.

I have ghosted many forums on as I have attempted to learn things throughout the years. This is the first I have joined. The educational approach here is amazing.

Thank you all again!

 

[Ezana4CE]

@Hate The Rain
No problem