Alternatives to foot pounds of energy (fpe)

[beerthief]

I haven't been following this even though I started it. I'm glad some found it an interesting topic. That additional factor, Matt, is something I might add to my spreadsheet. Or perhaps I'll find a reasonable way to post it and you or others can. I do not often look at all those numbers but it doesn't take up much space in the spreadsheet to add another column.

I agree with "Bedrock Bob" on minimum powder burner for coyotes. I also agree that no air rifle can realistically work as well as an accurate 223 (or 22/250) for coyote hunting. But if you can get a short range shot I remain convinced a 357 air rifle is a reasonable choice. I don't have one so I've never tested penetration and I would do that first. I haven't even calculated another measure I like to look at which is the area of the projectile versus the area of the target. I used it to calculate a 177 pellet damages about the same amount of the area of a squirrel as a .75 inch projectile would in a deer. That convinced me that a 177 was a reasonable choice and I've since used one to take >10 squirrels. While I have not done the math I think a .35 diameter hole through a coyote would work OK. I doubt that a 223 expanded would make a bigger hole. Penetration must be adequate too and I would test that before using it on game.

To me, looking at the area of the projectile versus the area of the target animal and the penetration depth of the projectile from the subject airgun are best and are still not terribly time consuming or costly to obtain. I think they are better than any formula. It will weed out what I consider unsuitable projectiles. In my most recent penetration test I included metal mag pellets, for example. They only made it through 3 or 4 wet magazines. My standard for squirrels is 9-10. They expand nicely so there is no problem at all with the hole size but there is a risk that they won't go deep enough for a clean kill.

It does not apply to airguns but fast moving PB projectiles can also damage more tissue than the diameter of the projectile due to rapid expansion of the animal tissue. That sort of expansion is shown in ballistic gel tests and with something like a 223 the area of the cavity in the gel will be damaged animal tissue. But with an airgun (or a handgun) that tissue just goes back to where it was. It is not permanently damaged. So I don't do much with ballistic gel tests for airguns. It's another reasonable way to test penetration but I don't think we should look vary hard at the admittedly cool looking cavity.

I like looking at some numbers because it gives me some idea of the suitability of a gun or round before I buy them and start testing them. It is not sufficient in my mind by itself but it is useful as long as you don't treat it as the final thing to be considered. I like alternatives to fpe because very, very few airguns meet the PB criteria of 1000 fpe for deer. Very fuel black powder guns or handguns do either but both have been used effectively for a century or more. So fpe must not tell the whole story. Other measures may help get a more clear idea for large slow moving projectiles.

a guy i met uses road kill to test on actual animals . he also uses road kill deer as bait to Yotes , placed at a known distance and left for a few days to attract and "get comfortable " kind of messy but very effective .

 

[Bedrock Bob]

A bullets performance at the target can't be estimated by fpe. Nor can you extrapolate much about it.

You can hypothesize all you want about speed, diameter and weight. When you send one down range it carries all those numbers with it in a nice equation.

But what it does downrange is determined by the mass and resistance it meets at the target. That's where all those calculations come to earth.

You can go between the ribs, through lungs and right out the other side with little expansion. Or you can hit bones from shoulder to shoulder. You can crack a cranium like an egg. Or go through ligament and cartilage. All are going to make your formula result in different outcomes.

With pellets and slugs at airgun speeds you aren't dealing with much expansion potential nor a wound channel maximized by shock. Primitive rifles as well. Lung pass throughs that close up are common. Killing shots take more time to be effective. Getting the projectile to the target with enough energy to penetrate a hypothetical depth of flesh is important but it's only as important as the mass and resistance of your target and the giblets it passes through.

You can have an excess of energy on paper but your target dictates the amount of energy that's transfered to the kill.

Then there is bullet design. A huge factor in how the energy from the calculations are transmitted to the target. Airgun projectiles at airgun speeds don't have much in the way of terminal performance.

So how much energy do you need to shoot a coyote with an air rifle (or any rifle)? That's like asking how long it takes to dig a hole. It's not all about the size of the shovel and how fast you can dig. It's about how hard the ground is and how much gold you get at the bottom.

No matter the numbers an air rifle will take time to kill in many cases. Those calculations hit the animal and then a hunter starts calculating how far it is to the neighbors fence line and how far his target will go before it falls.

A rodent flops around or drops in a hole. A bird can't fly and you chase him around like a fool to get him. A skunk goes up under the barn and stinks for a month. A coyote will run a quarter mile and dive into a bush.

How much FPE do you need to shoot a coyote with an air rifle? All of them. How much to pass through his entire body for a potentially lethal shot? Just a few.

 

[Vetmx]

I firmly believe in the "there's more than fpe" involved.
Years ago I was hunting with a black powder 50 cal and blew right through a ram, knocked it right over, and seconds later it got up. The second round put it down. Inspection showed the exit wound was the same size as the entry. Small..............
Back home after the trip I switched slugs. The one I was using was obviously packing plenty of fpe but,,,,,,,,,,,
The slug I switched to performed much better at basically the same fpe. I shot a buck that made it about two steps and never moved again. Small entry wound, the exit was the size of my fist.

But the bottom line is a hole through the lungs or heart, no matter how big spells death. There’s no way around it. Even if an animal ambulance is waiting nearby. All the coyotes I’ve shot with a .22, .25 and .30 slug have traveled a distance before expiring with a boiler room shot. My airguns kill them just as dead as my 6mm. But my 6mm’s energy is just more than their little legs can bear most times and they get blown over. But I’ve shot them with a 9mm and they kicked in the afterburners until the lights went out. Just like an airgun.

This is why I originally said I rarely, if ever concern myself with FPE. Common sense with what I’m shooting and what I’m shooting at with regards to full penetration is all I concern myself with. You can have enough FPE but if you’re using the wrong projectile and hit the shoulder, you’ll fail. So you are correct, there is more than FPE involved. It’s called truly knowing what you’re doing through testing and experience.

 

[Vetmx]

Because I’ve killed coyotes with about everything and they keep being brought up in topics, I dug up a picture. Do you think a 325gr bullet in 45 caliber that has 2,880 FPE is enough to keep a coyote from making it out of your yard after shot. I shot this one from my stand and blew the heart completely out of it. Also took out a tree after the bullet exited. It ran 70 yards. Had to blood and organ parts trail it. We can’t control everything. But what we can control is always using enough gun with the right projectile in airgun land. Some animals are just tough and you’ll have to look for them if you want to check out the dead body and do an autopsy to confirm your setup. FPE numbers are one thing, but the right projectile is probably more important. It can help you if you’re borderline on FPE.

 

[BlackICE]

If you desire DRT with an airgun on a yote, a brain, or spinal shot below the brain is the only way to go!

I don't have 1st hand experience, but I have seen videos and believe that if you go for a double lung shot using a 220 Swift, 22/250, with the right expanding varmint bullets within 200 yards the yote ain't going to move very far. A double lung shot 458 Win mag with non-expanding bullets, good chance it will run some, not that much better than a big bore airgun.

 

[JimD]

Interesting experiences. Elmer Kieth (credited with the invention of the 44 magnum) liked hard cast flat nosed bullets. Sort of like a semi wadcutter. He was hunting with his big pistols but speeds are reasonably similar to airgun velocity. I wonder if a flat nosed slug wouldn't work better at least for larger animals than the hollow points that seem to predominate. Deep penetration but with more of a blow than a round nosed bullet.

 

[Vetmx]

Interesting experiences. Elmer Kieth (credited with the invention of the 44 magnum) liked hard cast flat nosed bullets. Sort of like a semi wadcutter. He was hunting with his big pistols but speeds are reasonably similar to airgun velocity. I wonder if a flat nosed slug wouldn't work better at least for larger animals than the hollow points that seem to predominate. Deep penetration but with more of a blow than a round nosed bullet.

Interesting thought. I wouldn’t hesitate to try them but I want them all lead.