Speed lose formula?

[iAMzehTOASTY1]

Is there a formula for how much speed a pellet loses over a given distance?
Say ot leaves the barrel at x(800fps) at 10 yards its going Y....20 yards...? Is that a thing?...

 

[Revoman]

I know that Strelok Pro has that information built into the chart as an option, but you're asking for a formula that likely changes with each pellet weight.
mike

 

[Neu]

FPE Calculator | Retained Velocity | Pyramyd Air

Calculate power output, muzzle energy and more! Whether you need an FPE Calculator, Ballistic Coefficient, or Wind Drift with Pyramyd Air's shooting calculators

www.pyramydair.com

 

[Ballisticboy]

There are the standard flat fire equations but, as you can guess, they assume the pellet flies flat which it does not, and they assume the drag coefficient is constant which it isn't, at least at speeds above 700-800 ft/sec depending on shape. Having said that for short ranges at lower speeds, they will give a rough figure.

You have to know the drag coefficient of the projectile as well.

 

[durbs75]

It’s basic ballistics! There’s many calculators out there!!

 

[ctshooter]

Is there a formula for how much speed a pellet loses over a given distance?
Say ot leaves the barrel at x(800fps) at 10 yards its going Y....20 yards...? Is that a thing?...

Yes - it is called ballistic coefficient, or BC. You'll see there are many threads which discuss this here. As mentioned above there are lots of calculators out there to get the data you are looking for.

There are tables which list general BCs for many projectiles, but this is only a starting point. BC changes based on velocity, so your starting muzzle velocity will change the BC slightly from that listed in the tables.

 

[Hateful McNasty]

https://www.straightshooters.com/ourtake/ourtaker9.html

Ya, like from the chart in that you see how some fair vs others. Even like weighted. One may just take a beating vs the next. You just got to do yoir own math on your gun and any pellet used in it

 

[dgeesaman]

Yes - it is called ballistic coefficient, or BC. You'll see there are many threads which discuss this here. As mentioned above there are lots of calculators out there to get the data you are looking for.

There are tables which list general BCs for many projectiles, but this is only a starting point. BC changes based on velocity, so your starting muzzle velocity will change the BC slightly from that listed in the tables.

Confirming that the formula you want involves ballistic coefficient. More BC, more velocity retained as the pellet travels over distance. The wind drift is directly related to how much velocity is lost through the trajectory. (So high BC = more velocity at the target and less wind drift).

Using a LabRadar, I’ve found my airguns so far shoot a ballistic coefficient that varies slightly with target distance but varies much more greatly as a baseline from the published values. So I take published BC as a guideline not a guarantee.

I may have found the raw formula at some point but for convenience I use a ballistic calculator software like ChairGun.

In other words, my data shows that it’s far more important to get a BC for a given projectile in your airgun than it is to account for how that bc varies with target distance.

I was applying basic G1 BC models to pellets and slugs in the 700-900fps range. I did not attempt any other BC models.

 

[iAMzehTOASTY1]

Much appreciated replies; was half asleep thinking again

 

[starlingassn]

chairgun will tell you what you want to know young grasshopper


for instance,
my .25 impact compact
running 34gn jsb king heavy at 872fps at the muzzle,

is going 756fps at 50yds,
and 667fps at 100yds.

 

[qball]

hope you have strelok pro, just check the drop table which can be configured with speed.