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stewartlittle · Member

I was looking at straight shooters site and looking at the velocity chart and had a question.

I noticed in the RWS48,the JBS Exact Heavy has 12 ft. lbs. at 50 yards in .177 caliber and 12 ft.lbs. in the .22 as well a 50 yards.Only the CP Premiers in .22 shoots a tad harder at that distance.

Is 12 ft. lbs. the same in both calibers?I mean do they both have the same knock-down power as long a ft. lbs. is the same?

Still aint got another air rifle yet,but think I narrowed it down,

Get the 48 again but a refurb,at present time Umarex only has .177( which I thought of getting).
Or get a R9 .177 caliber,although it has less power.

And last,how can a heavier pellet shoot faster than a lighter pellet out of the same gun?

Rogerflat · Silver Status Member

ft/lbs of energy is a function of velocity and mass, and is similar to the old riddle of what weighs more, a pound of feathers or a pound of lead?

They are both the same regardless caliber.

The only difference is the size of the hole left in the animal.

Slavia · Moderator

cw · Banned

You're thinking of

stewartlittle · Member

j.m. · Member

Because a .22 pellet would most likely have more mass, it would penetrate farther than a .177 pellet would.

For example, you wouldn't want to shoot a rat in the head with this if you expected anything left:
http://www.pyramydair.com/cgi-bin/model.pl?model_id=963

cw · Banned

You don't want anything smaller than .22 caliber for hunting.

Roy · Veteran Member

Models of the same air rifle bored for larger calibers are slightly more efficient in utilizing the energy of the spring; the kinetic energy will be greater. Ballistics tables generally reflect this. The reason for this is what Remington(forgive me for the firearms reference) once called "the piston principle" where the increase of sectional area upon which the expanding gases act more than offsets the increased friction of the larger circumference.

Penetration, in nonexpanding projectiles with the same point shape, is proportional to the energy/sectional area ratio. This is a simplifcation applicable to hunting dangerous African game(I've never done it) where steel jacketed bullets are needed to reliably punch through several feet of tough hide, muscle, and bone.
For fun, calculate the relative penetration of a 500 grain .458 solid with 5000 foot pounds of energy(elephant load) versus a .50 BMG @12,000 fpe. Then compare a .177 pellet at 13fpe to a .22 @ 14 fpe. Which of these pellets will penetrate the deepest?

The preceding paragraph really doesn't matter because pellets expand upon impact changing their penetration characteristics completely.

And if the pellet "overpenetrates"(goes through) some of the energy is lost.

The .22 has a reputation as a better killer than the .177. But for very precise shooting where range estimation is critical, such as shooting tree squirrels in the brain, go with the .177, as it has a flatter trajectory.

In any event, the most important factor contributing to your success is your shooting skill. That means PRACTICE, PRACTICE, PRACTICE !

Pellets expand upon impact

j.m. · Member

An accurate gun also helps.

thepaladin · Senior Member

I tend to agree with cw (possibly a first huh cw?) in that I don't like the idea of using anything smaller than a .22 for hunting (though I would use a good .177 on some birds I suppose). But in this foot pounds of energy are only part of the story. A .22 is heavier than a .177 so it will fly in a different arc. The shape of the pellet you use will even change depending on what you intend to use it for.

You can't say though that a given gun will produce a given energy with a particular calibor. The different pellets will sometimes also effect the energy delivered. It will be close usually but there will be some differences. I went with the .25 when I bought the Falcon Hunter because I wanted to take advantage of the power to use a heavier pellet. There are actually claims that you can get more energy from the .22
http://www.pyramydair.com/p/walther-falcon-air-rifle.shtml
but as I said, that's not the whole story, and it all depends on the rest of the facts about each given pellet.

stewartlittle · Member

cw · Banned

W(V²=K

There is implied .jpg[/img]

stewartlittle · Member

Nope,the one on my LG phone is the most I've got,but I might can remember it or jot it down.

thepaladin · Senior Member

Here's a calculater that allows you to plug in weights and speeds and will figure it for you...easy huh? Rolling Eyes

http://www.airgun1.com/articles/kineticenergy.html

Roy · Veteran Member

Stewartlittle,

Sorry ! I was merely trying to provide additional information to help raise your level of understanding. Allow me clarify-

The .50BMG is the Browning Machine Gun round now chambered in some shoulder fired "sporting" arms available in the US. I mentioned it, and the .458 elephant caliber "for fun" because they have amazing penetration power, the .50 even more so. Just something to think about. I now realize this just muddled-up the post. Then, without a proper transition, I proposed the comparison of our hypothetical nonexpanding .177 pellet @13fpe to the .22@14fpe to show that the .177 would have more penetration potential, despite it's lighter weight.
Why discuss nonexpanding hypothetical pellets ? To form a basis of understanding upon which to build. Then we toss in all the variables of general expansion and pellet specific expansion. Next an answer to your question of "what is overpenetration?", the phrase Slavia used as yet another variable(agreed). Your use of the phrase "knock down" power implies a hunting situation, so I offered the example where
brain shooting squirrels is one application where the .177 is preferable to the .22, because pellet placement is far more important than any considerations of energy transfer.
I agree with Rogerflat; energy is energy, but knockdown(killing) power is something else again.

I stand by my statement regarding efficiency in the larger calibers; yes there are exceptions.