PCP Air Rifle Consistent Shots – Does Pellet Weight Change It?

Here’s a question that has exercised me for some time. If we measure the number of PCP air rifle consistent shots, is it changed by different pellet weights?

I have never seen this aspect of PCP air rifle performance discussed before. So I decided to do it myself. The results are surprising – read on to find out!

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PCP Air Rifle Consistent Shots – Defining The Issue​

In other words, do we achieve more consistent shots from a regulated PCP when shooting heavy pellets than with lighter ammo? Or the other way round? Or does it make no difference?

For HAM air rifle reviews, we always produce data and a chart for this performance. We call it the “shootdown test”. This is always undertaken with a suitable “mid weight” pellet. For example:

But I have never tried this test on the same air rifle using pellets of different weights. Until now…

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PCP Air Rifle Consistent Shots – Test Protocol​

To examine this issue, we need a test protocol. It’s not complex or difficult, but just needs to be repeated consistently multiple times.

As I have just undertaken a shootdown test on the Umarex Notos G2 as part of our comprehensive test review, this seemed a good gun to use for a number of reasons:

1. The regulator performance is outstanding!
2. The gun displayed a clear “break” where the regulator set point is reached. So it’s easy to count the consistent shots.
3. The Notos G2 has a conventional “poppet-style” valve, operated by a conventional hammer and hammer spring. So, it’s a representative average PCP configuration.
4. We have one test already completed, with “mid weight” 15.89 Grain JSB Hades pellets.

For consistent filling, I used a Benjamin Traveler HPA compressor, set to a consistent shutoff pressure of 3,600 PSI. The gun was filled before each test, then allowed to cool and topped off before starting the test.

The gun was fired on magazine feed (except for the 32.4 Grain Eunjins as they are too long to fit in the magazine). Why 45 shots per test? Well, that’s 3 full magazines capacity for the Notos G2.

To be clear, no changes were made to the gun. The regulator and hammer spring settings were identical in each case and as set by the factory.

Let’s go…

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PCP Air Rifle Consistent Shots – Summary Results​

To add to the existing shootdown test undertaken with 15.89 Grain JSB Hades pellets, I also tested the gun in the same way with four other pellets. The aim of the exercise was to make comparable tests with the widest-possible range of pellet weights, as follows:

H&N Field Target Trophy Green	RWS Hobby	JSB Hades	JSB Jumbo Monster	Eunjin
9.57 Grains	11.90 Grains	15.89 Grains	25.39 Grains	32.40 Grains

Here’s the summary chart of results.

Overall comments are as follows:

1. The Notos provides extremely consistent regulated velocities with all pellet weights.
2. The lighter pellets shoot faster – of course – than heavier ones.
3. After passing the regulator set point, muzzle velocity falls faster with light pellets than with heavy ones (at least out to 45 shots). I had never thought about that before.
4. The heaviest pellets gave more shots before reaching the regulator set point. That I did NOT expect!

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PCP Air Rifle Consistent Shots – Detailed Velocity Results By Pellet​

Now let’s zoom in to that summary graph to find the precise number of shots achieved before reaching the regulator set point for each pellet. It’s the same pressure in every case, of course.

In each case, the “Y” (vertical) axis of our chart is extended to cover a range of 100 FPS (although the values are different in each chart). All the charts cover 45 shots on the “X” (horizontal) axis.

Working from lighter to heavier pellets, this can be seen easily as follows…

Let’s now summarize those charts in this table.

H&N Field Target Trophy Green	RWS Hobby	JSB Hades	JSB Jumbo Monster	Eunjin
Pellet Weight	9.57 Grains	11.90 Grains	15.89 Grains	25.39 Grains	32.40 Grains
Shots To Regulator Set Point	31	31	29	36	40
Average Consistent Muzzle Velocity	891 FPS	827 FPS	780 FPS	635 FPS	561 FPS

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PCP Air Rifle Consistent Shots – Power Comparison​

OK, that’s fine for Muzzle Velocity. But what about power?

For most airgunners, power is far more important than velocity. And this is where we find the biggest surprise in this comparison test.

You see, not only did the heaviest pellets give the greatest shot count, but – as we always find – they also generated the most Muzzle Energy per shot.

So this is the surprise. That means that the TOTAL Muzzle Energy from one fill of High Pressure Air is almost twice as much for 32.40 Grain pellets than it is for 9.57 Grain pellets, as we can see below. WOW!

In other words, given that we have the same amount of air at the same fill pressure and same regulator pressure in every case, the Notos G2 is considerably more efficient in generating shots with heavier pellets than with lighter. That – I believe – is typical of most all PCP airguns, but it’s very clearly demonstrated by this test in a way I’ve rarely seen before.

H&N Field Target Trophy Green	RWS Hobby	JSB Hades	JSB Jumbo Monster	Eunjin
Pellet Weight	9.57 Grains	11.90 Grains	15.89 Grains	25.39 Grains	32.40 Grains
Average Energy Per Shot To Regulator Set Point	16.9 Ft/Lbs	18.1 Ft/Lbs	21.5 Ft/Lbs	22.7 Ft/Lbs	22.6 Ft/Lbs
TOTAL Muzzle Energy to Regulator Set Point	523.5 Ft/Lbs	560.7 Ft/Lbs	623.0 Ft/Lbs	817.4 Ft/Lbs	905.7 Ft/Lbs

So now we know the answer. Pellet weight DOES make a difference to shot count for PCP airguns. With the Notos G2, we achieved more consistent shots from a regulated PCP when shooting heavy pellets than with lighter ammo, together with a lot more power.

I hope you find this analysis interesting – and possibly useful. There’s always something new to discover about our airguns!

BUY FROM PYRAMYD
Umarex Notos G2 PCP Air Rifle 0.22​

The post PCP Air Rifle Consistent Shots – Does Pellet Weight Change It? appeared first on Hard Air Magazine.

 

[Linehauler73]

Makes sense to me with everything else being equal but pellet weight, the heavier the pellet the more back pressure created thus closing the valve ever so slightly faster using less air . Why if you are a perfectionist in tuning results you have to slightly tweak hammer tension for a given reg pressure when changing just the pellet weight to continue to maintain a perfect tune.

 

[hameditor]

Personally I don't have a comprehensive explanation or theory for this yet.

What I have are the test results achieved with one specific PCP airgun with careful, precise testing. That I can stand behind.

Are these results typical for other PCPs? Dunno.

I think there would be much to be learned by similar tests on other PCP airguns. The issue - as always for me, at least - is getting the time to do so.

In my mind, the design elements that come into play here are likely to include:
Hammer weight
Hammer spring spec
Valve return spring spec
Valve poppet travel
Valve poppet dwell time
Air volume between closed (?) valve poppet and pellet at the moment of firing
Regulator pressure
Barrel length
(Possibly) plenum volume

But I'm sure of this. A fulsome explanation of these results is waaaay beyond my pay grade!

 

[Solo1]

Well ill try to give you some more data in a few days i have what i feel is a very good tune on my drs 500 with 21.9 aea at 950 and it gives 20 shots on reg. It will also push 25.3 aea to 912 i just need to shoot down from full.

 

[Solo1]

I’m see it along the same lines, to me it’s like tuning with pellets. But if the end result isn’t effective at the target, then what good is it?

I feel that a perfect tune air pressure is basically equalized just before the pellet leaves the barrel therefore there is no excess air or pressure acting on the pellet after its out therefore no disturbance to its flight which should give the most precision down range.

 

[FL22]

I feel that a perfect tune air pressure is basically equalized just before the pellet leaves the barrel therefore there is no excess air or pressure acting on the pellet after its out therefore no disturbance to its flight which should give the most precision down range.

I have seen this, not going to lie it’s because I did things wrong or shouldn’t have and seen the results.

 

[Solo1]

I always like when you see little clover leaf holes on target it tells me that harmonics are good too.

 

[Solo1]

Well i just shot 21 shots through the 500 and got 20 shots on the reg with 25.3 aea i deleted the shot that went below 900

 

[Solo1]

Hey this might be a good way to check your tune- if you get more shots with a heavier pellet you could cut back a bit on your light pellet tune

 

[Papa-Smurf]

I feel that a perfect tune air pressure is basically equalized just before the pellet leaves the barrel therefore there is no excess air or pressure acting on the pellet after its out therefore no disturbance to its flight which should give the most precision down range.

How can you tell if you've reached this state of equilibrium. I've heard people say you can tell by the sound. ?????

 

[Madhatter]

Looks like back pressure might be causing the valve to not be able to release the same volume of air.

The pressure in the barrel stays higher longer due to the slower Acceleration of the heavy pellet. The valve closes in around the same amount of time as with the lighter pellets. So with more back pressure the amount of air volume flow will be less.

 

[Madhatter]

How can you tell if you've reached this state of equilibrium. I've heard people say you can tell by the sound. ?????

If the pressure is still flowing out of the barrel after the pellet/slug has left the barrel it's just wasted air volume which will cause it to be louder.