Setting the power on a new PCP

[Ultrastu]

That is the formula .

Pcp more energy with heavies

Springer more energy lights

 

Generally

[Mice!]

Very nicely done stu, hope that clears it up for everyone, well one🤔

 

Taking the above info if the pcp is using the falcon pellet and he has it doing say 11.6/11.8 then three other pellets take it over, like everyone said.

[Ultrastu]

Just as a side note, at high fac levels the difference between pellet types can make as much as 10 fpe difference .

 

An airguns muzzle energy is never really set as it ALWAYS depends on the pellet type .

So in .177 i always check with falcons exact and bismags all my guns springers and pcps .and adjust the guns energy to be nicely legal with the most efficient .

[Mice!]

I was surprised that spring and pcp were so different, I new the fpe would change with pellet weight but thought they would both follow same lines.

[Ultrastu]

Ah well .the reason why they behave differently .is due to the air blast that drives the pellets .

In a pcp its a relatively low pressure long burst of air .thats why a pcp with a long barrel can accelerate the pellet up to higher speeds or increase shot count .

On a springer the air blast is VERY high pressure 300 -400 bar .but for a very short duration so a ling barrel can actually slow the pellet down as there can be very little air left driving the pellet when it gets to the end .

This is why its often said that you can cut a springers barrel shorter without loosing energy . (Not possible on a pcp .)

 

This short high pressure air blast in a springer can often increase the bc of a pellet compared to a pcp .

Typical bc values of jsb exact between my 2 guns above (as you can see they both make about 11 fpe ) is 0.021 for the pcp and 0.03 for the springer .this means that although the 2 guns have to same energy at the muzzle .the springers pellet retains more of its energy down range and hits with significantly more energy

[Gonk]

Very interesting and informative Ultrastu, thanks for taking the time out to do this 👍🏻

[Hendrix's rifle]

That's why if police check air rifles they use a range of different pellets to see if it goes over the limit with one of them nice test

I am not. The equation is correct but you dont understand it. The rifle power once set is fixed. Changing the pellet mass will alter the velocity not the power. The equation shows you how mass and velocity are related but power is fixed and is only changed by manual adjustment.

 

You cannot alter the power of your rifle by changing the pellet. Dont get confused by how ftlb drops with distance. Thats a different thing.

In a pcp all it does is let out the same amount of air each time, the rest of it is up to the pellet

[Ultrastu]

Yes in a regulated gun thats about right .

But not in a unregged gun .

As the gun goes through its shot charge from say 200 bar down to 100 bar the air delivery changes .

So at first the air burst delivered to the pellet is high pressure but short duration .as you take more shots the pressure drops but the firing valve gradually allows the valve to stay open a bit longer allowing a longer pulse of air eventually you get to 100 bar where the pressure is now lower but the duration of the air is a lot longer

[Ultrastu]

Very interesting and informative Ultrastu, thanks for taking the time out to do this

Thanks mate much appreciated .

[Mice!]

Anyone seen DC??

 

The facts are there in black and white, are you now a believer?

[Hendrix's rifle]

Yes in a regulated gun thats about right .

But not in a unregged gun .

As the gun goes through its shot charge from say 200 bar down to 100 bar the air delivery changes .

So at first the air burst delivered to the pellet is high pressure but short duration .as you take more shots the pressure drops but the firing valve gradually allows the valve to stay open a bit longer allowing a longer pulse of air eventually you get to 100 bar where the pressure is now lower but the duration of the air is a lot longer

Wasn't going that in to detail 😂😂😂😂

[Guest]

Hi, just seen the data. Ultra thanks for doing this and holy crud look at the variation! I knew heavier pellets were more efficient for a PCP and so expected a small variance, but not this much! I was clearly confused by actual power vs measured. Someone else put it very neatly: the gun delivers the same force each time but what happens next is up to the pellet. It's all down the pellet......which is very troubling to me.

 

The Ultra's figures varied by 11%. The springer by even more. Which begs the question: how do you actually know what your gun's ftlb rating is when it comes out of the factory?

 

Thanks again, Ultra. I've learned a lot from this thread .

[Hull wolf]

Heavy's in a PCP gives the highest Power no it doesn't tried bismags in my HW 100 ks and I had a power of 10.5 ftlbs

JSB Jumbo's 15.89 gave a power reading of 11.5ftlbs ..

.

Edited June 10, 2017 by Hull wolf

[Ultrastu]

As always said .every gun is different .

My mate had a hw98 for a while and it basically made the same energy with every pellet we put through it .

Very little energy difference.

Air arms guns are known to produce less energy with bismags often as a bis mag has a very large head and skirt size and this can cause extra drag in a tight lotherwather barrel .especially in .22 .

[Ultrastu]

Hi, just seen the data. Ultra thanks for doing this and holy crud look at the variation! I knew heavier pellets were more efficient for a PCP and so expected a small variance, but not this much! I was clearly confused by actual power vs measured. Someone else put it very neatly: the gun delivers the same force each time but what happens next is up to the pellet. It's all down the pellet......which is very troubling to me.

 

The Ultra's figures varied by 11%. The springer by even more. Which begs the question: how do you actually know what your gun's ftlb rating is when it comes out of the factory?

 

Thanks again, Ultra. I've learned a lot from this thread .

Your welcome dc .but as ive stated the above is a trend only and its often broken with individual guns .

 

The answer is you dont know what your gun is doing unless you test it with a variety of pellets .jsb light med and heavy are usually the best place to start .

Also the legality of your gun is 100 % your responsibility. so owning a chrono is as essential as owning pellets .

[GingerCat]

Ultrastu has done some excellent work and it's without fault. It's basic science and math so I don't get why people are arguing.

What's interesting is the minimal differnce to poi and shot count vs the 1ftlb loss of power.

Something I shall look into.

[Guest]

That was my mistake. The science & maths are simple but the fickle nature of pellets gives you unexpected results.

[Ultrastu]

That was my mistake. The science & maths are simple but the fickle nature of pellets gives you unexpected results.

Very true mate .

Just when we feel we have it figured out something breaks the rules and proves us wrong .

I had that recently when tuning a bsa ultra it just wouldnt do as i expected

[Guest]

Very true mate .

Just when we feel we have it figured out something breaks the rules and proves us wrong .

I had that recently when tuning a bsa ultra it just wouldnt do as i expected

 

Out of interest, what do you think the power rating is for a .22 Ultra SE? From your figures, and the published muzzle velocity I'm thinking 10.1? Putting that into Chairgun and it's pretty close to my range yardages.

[Ultrastu]

Most likey the pellet that would gibe the highest energy would be 16 grn jsb jumbos (aa fields )

Id expect about 10.9 -11.2 fpe with them .

When i bought one last year thus is what it did with jumbos .

Bsa pcps have a tendancy to increase a bit in energy after a tin or so of pellets from new .

This is well known by bsa so they tend to set the guns initially around 10.7 fpe .knowing it may rise to 11 .3 ish

Personally i like the 13.4 grn falcons or jsb rs .these shoot flatter and kill better in my experience than the 16 grn .pellets but do have a touch less energy around 10.8 - 11 fpe when run in .

[Guest]

Most likey the pellet that would gibe the highest energy would be 16 grn jsb jumbos (aa fields )

Id expect about 10.9 -11.2 fpe with them .

When i bought one last year thus is what it did with jumbos .

Bsa pcps have a tendancy to increase a bit in energy after a tin or so of pellets from new .

This is well known by bsa so they tend to set the guns initially around 10.7 fpe .knowing it may rise to 11 .3 ish

Personally i like the 13.4 grn falcons or jsb rs .these shoot flatter and kill better in my experience than the 16 grn .pellets but do have a touch less energy around 10.8 - 11 fpe when run in .

 

Thanks again Ultra. I'll work on 11.0 for now but I've submitted an email to BSA. So let's see what they come back with.

 

AA DFs 16Gn do work nicely with the Ultra but I'm going to test out 14Gn now as well.

[Ultrastu]

What did you ask bsa ?

[Guest]

I asked what power the SE was set at.

[Guest]

BSA Response:

 

Thank you for your enquiry.

 

Our products are tested using a wide variety of pellets such as BSA Red Star, JSB Exacts Bisley Magnum and H&N Field Target Trophy.

 

I suggest you set up your rifle using 16 grain JSB Exact pellets which are a mid - range pellet weight and will give you velocities of approaching 570 ft/sec and kinetic energies approx. 11.5ft.lbs.

 

Please note the figures quoted are nominal - they may be slightly higher or lower than those published.

[Ultrastu]

How can bsa expect you to set your guns energy with their anti tamper in place