Some Thoughts on Airgun Killing Power

[Doc Sharptail]

I've been playing with some numbers this afternoon, and I'll throw this idea out there just for discussion.... It is similar to the long standing idea of having a minimum of 1 FPE of energy per pound of body weight of the target.... I am a firm believer in the relationship between momentum and killing power.... While things like the Meplat diameter affect the diameter of the wound channel, and the sectional density (or the sectional density but using the meplat diameter instead of the caliber) affects the penetration.... you still have to hit an animal hard enough to kill it.... and the bigger it is, the harder you have to hit it....

The momentum of a bullet at impact is the weight in lbs. times the velocity in fps.... That works out to the weight in grains divided by (7000 times 32.4) times the velocity in fps.... ie W (gr.) x V (fps) / 226,800.... The resulting number would be about 0.8 for a 200 gr. bullet travelling at 900 fps.... pretty hard to relate to the weight of an animal.... If instead of dividing by 226,800 we divide by 1000, the number is now 180.... hmmmmmmmmm.... would a 200 gr. bullet travelling at 900 fps (at impact) drop a 180 lb. animal?.... I would think that would be pretty close....

Here are some other examples....

8 gr. @ 450 fps = 3.6 lbs (low powered .177)
8 gr. @ 900 fps = 7.2 lbs (high powered .177)



Bob

Let's not get any misconceptions going here- it will save a lot of actual "in the field" grief...

First off, a pellet is a pi$$ poor projectile to hunt with- especially at the lower end velocities alluded to at the start of the list. If you aren't capable of head shots at those low velocities, don't shoot. Those low velocity numbers in .177 are extremely marginal on live game- anything other than a head shot will result in a wounded animal on the run or fly.

I think we need to see more on terminal ballistics- how various projectiles behave on impact. Most pellets I've seen at low to mid range velocities are over-penetrators- they simply pass through the game without expanding... a precise hit in the vitals, or head becomes the absolute minimum requirement.

Your numbers make more sense to me in the .30 cal/9mm range and up- they equal what is seen from most powder burning handguns.

Regards,

Doc Sharptail

[rsterne]

I think you are absolutely correct when it comes to the lower velocities.... Consider, however, that even at 450 fps the numbers quoted meet the 1 FPE per lb. of body weight recommended for many years as a minimum.... and at 900 fps they are 2 FPE per lb..... No question that at 1 FPE per lb. you need to be able to make a head shot or you shouldn't be taking the shot.... Any of these "rules of thumb" break down when pushed to unreasonable limits.... Even the famous Taylor Knockdown Formula says that a baseball thrown by a professional pitcher has greater knockdown power than a .500 Nitro Express.... I don't think many great white hunters would consider that a suitable projectile for hunting elephant, however....

It is interesting that you should mention that over-penetration occurs at low velocities and offer that as an argument against my suggestion for the lower powered guns.... That very penetration is considered an advantage by those that argue for the effectiveness of .177 pellets on larger game such as Racoons, providing the shot penetrates the fuse box.... Far from being unethical hunters, these individuals study the anatomy of their prey, and take into account the angle of the shot and the bone structure in the way before pulling the trigger.... While I'm not good enough to even try dropping a 'coon with any .177, their string of 1-shot kills (and lack of wounded animals) is impressive....

There is no question that shot placement is King.... and especially with the limited power of an airgun.... It was not my intention to argue otherwise....

Bob

[Doc Sharptail]

I think you are absolutely correct when it comes to the lower velocities.... Consider, however, that even at 450 fps the numbers quoted meet the 1 FPE per lb. of body weight recommended for many years as a minimum.... and at 900 fps they are 2 FPE per lb..... No question that at 1 FPE per lb. you need to be able to make a head shot or you shouldn't be taking the shot.... Any of these "rules of thumb" break down when pushed to unreasonable limits.... Even the famous Taylor Knockdown Formula says that a baseball thrown by a professional pitcher has greater knockdown power than a .500 Nitro Express.... I don't think many great white hunters would consider that a suitable projectile for hunting elephant, however....

It is interesting that you should mention that over-penetration occurs at low velocities and offer that as an argument against my suggestion for the lower powered guns.... That very penetration is considered an advantage by those that argue for the effectiveness of .177 pellets on larger game such as Racoons, providing the shot penetrates the fuse box.... Far from being unethical hunters, these individuals study the anatomy of their prey, and take into account the angle of the shot and the bone structure in the way before pulling the trigger.... While I'm not good enough to even try dropping a 'coon with any .177, their string of 1-shot kills (and lack of wounded animals) is impressive....

There is no question that shot placement is King.... and especially with the limited power of an airgun.... It was not my intention to argue otherwise....

Bob

Perhaps I haven't gone into enough detail on my hunting situations.

I'm still getting it through my head that an air gun is not the equivalent of a 40 gr h.p. @ 1175 fps

My game is the littler edibles- grouse, and rabbits. I've taken both with .177 in the 700 fps range, and it ain't my favorite thing to do. A lung/heart shot on a rabbit with .177 is not the same as an identical shot with the afore-mentioned p.b. h/p .22 L.R. I see a lot of complete pass through with limited expansion- slight enough to cause slow, fatal bleed. I like to consider myself much more humane than that. Anything but a head shot on grouse in .177 is just asking for trouble with fly-off and die out of reach.

There are exceptions. The JSB Predator in .177 will take grouse cleanly- above 700 fps- fast enough for the nylon tip to do it's expansion work. The only fly in this ointment is that the .177 Predator is just a hair less than pin-point accurate past 20 yards.

I still have to find a suitable medium for expansion testing. The Crosman .177 Ultra Magnum Heavy 10.5 gr is very accurate out of all the rifles I've tried it in. It appears to be a fairly hard projectile, and I'm a trifle leery yet of testing them against live game.

I've come close, with used .5 micron carbon water filters as a test medium. The drawback here is the mess, and availability of spent filters...

I've got nothing against your numbers, and generally agree with them. What I'd like to avoid is heartbreak in the field- especially on the part of the neophyte air gun hunters that are trying it for the first time.

I like the deliberation, and concentration that air gun hunting provides. I've been passing up a lot of shots that are marginally questionable. There is a lot to get used to- with the low to moderate velocity air gun hunting game....

Regards,

Doc Sharptail

[bitterman]

Perhaps I haven't gone into enough detail on my hunting situations.

I'm still getting it through my head that an air gun is not the equivalent of a 40 gr h.p. @ 1175 fps

My game is the littler edibles- grouse, and rabbits. I've taken both with .177 in the 700 fps range, and it ain't my favorite thing to do. A lung/heart shot on a rabbit with .177 is not the same as an identical shot with the afore-mentioned p.b. h/p .22 L.R. I see a lot of complete pass through with limited expansion- slight enough to cause slow, fatal bleed. I like to consider myself much more humane than that. Anything but a head shot on grouse in .177 is just asking for trouble with fly-off and die out of reach.

There are exceptions. The JSB Predator in .177 will take grouse cleanly- above 700 fps- fast enough for the nylon tip to do it's expansion work. The only fly in this ointment is that the .177 Predator is just a hair less than pin-point accurate past 20 yards.

I still have to find a suitable medium for expansion testing. The Crosman .177 Ultra Magnum Heavy 10.5 gr is very accurate out of all the rifles I've tried it in. It appears to be a fairly hard projectile, and I'm a trifle leery yet of testing them against live game.

I've come close, with used .5 micron carbon water filters as a test medium. The drawback here is the mess, and availability of spent filters...

I've got nothing against your numbers, and generally agree with them. What I'd like to avoid is heartbreak in the field- especially on the part of the neophyte air gun hunters that are trying it for the first time.

I like the deliberation, and concentration that air gun hunting provides. I've been passing up a lot of shots that are marginally questionable. There is a lot to get used to- with the low to moderate velocity air gun hunting game....

Regards,

Doc Sharptail

I think you are going to need a nice high power PCP .22 or .25 to get close ot he same killing/shock power of a .22 lr.... Hunting with an airgun is less forgiving. pin point accuarcy is ideal for clean kills and shot placment is incredibly important for clean kills. Distance limits are also required for 2 reasons. One is the decrease in energy the father you go and second is can you hit a 1/4 or 3/8" target reliably at the distance you need to? Much less room for error.

With a .177 cpl @ 980 fps I took squirels out to 70 yards. All head shots 1 shot kills mind you they were in the top of a maple tree and if the pellet did nto finish them off the 100 foot drop might had something to do with it also.

Bruce

[Wanderer]

I just purchased a Benjamin Sheridan Traill NP All Weather .22 non-pal, mainly for some problem squirrels I'm dealing with. They are persistently causing me problems by getting into the attic and wreaking havoc. I also have a few nuisance racoons, which I figured would be too big for this air gun to handle.

I haven't tried the gun out on anything yet (I just sighted it in last night) but I also don't want to shoot something, only to wound it and have it run around wounded for hours/days/weeks etc...

Does this gun have enough power and will it be contingent on a head shot only?

[Fastair]

Bob I think you have done a good job on making this as simple as possible.
It is rule of thumb and should not be expected to be perfect.

[igojuone]

I'm new to air gun hunting and rather then start a new thread I'm hoping some one will answer the question of is there a .22 cal air rifle in the $300 or less range that would be suitable for hunting grouse, rabbits and such? If so could someone recommend a couple of choices. PM me so this thread doesn't go sideways. Thanks

As for the 220 gr @ 2500 fps out of a 30:06, that will take down a moose of 1500 lbs.

[Doc Sharptail]

Here's 4 .22 cal. Predators taken from a totally unscientific test medium- rubber backed office carpet. I shot these the other night at 4 ft. Upper 970-980 fps.



That pellet 3rd from left encountered something hard in the test medium- another pellet...

Regards,

Doc Sharptail