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broommaster2000 · Moderator

Some explanations on Airgun Ballistics. I hope to simplify things for newcomers, as some of them are often mesmerized by impressive pellet speeds. My goal is especially to keep this SIMPLE!

For Example:

A good entry level Gamo can probably shoot a .177 calibre 8.42 grain at 924 FPS which converts to about 16 FPE. This is a best case scenario.

Gamo rifles often do about 865 FPS at 14 FPE with those 8.42 grainers.

A Benjamin Discovery in .22 at about 20 FPE with 15.94 grain pellets shoots 750 FPS. Doesn't shoot as fast, but does contain more energy.

FPS = Feet per Second

FPE = Feet Pounds of Energy (ft/lbs)

Do correct me if I'm wrong. This isn't a thread about which rifle is better, just how powerfull they are and how they work. It's also to get the myth out of the world of high pellet speeds. They mean nothing. I felt the need for a sticky on this subject because a lot of people still have the wrong idea about fps. Power is not measured in FPS alone, you'll need weight and speed. Exclamation

Also, I get a bit tired of explaining this every time. Mr. Green

rsterne · Moderator

Another good reason not to be mesmerized by claims of high fps.... Once pellets are travelling in the transonic region (above Mach 0.8 = 900 fps).... they lose energy at a HUGE rate.... A "normal weight" wadcutter (ie 7.9 gr in .177 or 14.3 gr. in .22) starting at 1100 fps will lose about 100 fps (17% of it's energy) in the first FIVE YARDS.... Shocked

Look for an accurate rifle and select a pellet weight which keeps the velocity in the 900 fps range for best performance.... Wink

Bob

jeager106 · Member

O.K.
Published speeds are way big time exagerations.
Then what .22 airgun will give an honest 900 f.p.s.?
Not PCP, co2 or springer only. 900 fps would tickle me silly if I could find an air gun that would deliver such ballistics.

sniper · Silver Status Member

rsterne · Moderator

I've never owned one.... but a friend on another forum swears his BAM B-28 (RWS 350 clone) gets 880 fpr with 14.2 gr pellets stock right out of the box.... He has owned both that and a 350 and says the B-28 is actually more powerful.... and not from just one example but several....

Take it for what it's worth....

Bob

Slavia · Moderator

NZ Shooter · Suspended

I realise this is an old thread, but my Patriot .22 is sitting at 901 fps 10 shot average, with 15.43gn pellets. Just under 28fpe. It shoots sweet, and I do not endorse bulls**t.It's un-tuned, un-modified

radar · Silver Status Member

MSEO · Member

A heavier pellet at a lower muzzle velocity but with the same muzzle energy as a light pellet and higher muzzle velocity will retain more energy further down range. Drag force is lower at lower velocity and the more massive pellet will be less affected by a given drag force.

If you enter different weights in chairgun pro keeping the muzzle velocity constant, the muzzle velocity will change. Then switch on "energy" markers in the embellishment menu, you can see the energy is retained further out.

MSEO · Member

Sorry. Different weight keeping the muzzle ENERGY constant...

radar · Silver Status Member

Good post MSEO. Yes drag is a function of the square of velocity, like energy is. So long as a projectile doesn't hit the ground before the target, the heavies keep whatever they started out with further on, like you said. Penetration tends to be better, too.

airgunsarecool · New Member

I'd like to see some air gun/pellet tests on ballistic gelatin. Cool

radar · Silver Status Member

airgunsarecool · New Member

radar · Silver Status Member

Sure thing.
Here's another good one. This testing--by using the same air rifle in both .177 and .22 calibers--tends to indicate that momentum combined with pellet frontal area, rather than kinetic energy alone, is a major predictor of average projectile penetration.

Kinetic energy being a function of mass times the square of velocity determines total damage or displacement of the impacted tissue, along with the total amount of heat that is generated.

Momentum is a function of mass times velocity (not squared velocity) tends to be higher in heavier projectiles. Momentum, like kinetic energy is conserved, and tends to keep the projectile moving forward through resistance.

For example, a light projectile of a given nose profile, material, and frontal cross section traveling faster can generate the same impact damage, shock, and heat as the same design but heavier, slower projectile. But the heavier one will tend to generate less temporary cavity and penetrate deeper.

http://www.brassfetcher.com/Brass%20Fetcher%20Evaluates%200.177%20and%200.22%20inch%20airguns.pdf

-Rob