Caliber or Power

Both are true.  It's not strictly the larger size of the pellet nor the energy it's carrying when it arrives at the target.  The larger caliber operates on a larger area of tissue, thus has more opportunity to transfer a larger amount of energy.

With that said, I don't find "knockdown power" to be particularly useful predictor of hunting efficacy.  With airguns, shot placement is vastly more important than energy delivered.  Granted, making a bigger hole through the lungs or heart will more quickly stop them from doing the thing they're meant to do.  I'm just saying a .25 cal at 50fpe that misses the vitals is far less effective than a .177 at 10fpe that goes through the fusebox.  I've tried numerous hollowpoints and expanding pellets that propose to have tremendous knockdown power, and indeed some of them work very well...when they connect.  The issue I have with them is that they rarely have adequate accuracy at distances beyond 30 yards or so to be able to hit the small kill zone of a squirrel.  Meanwhile although a domed pellet does little more than icepick through the critter, I can put it into the brain and it's instant lights out.

If the shot placement is exactly the same, and the fpe delivered to the target is the same the caliber is inconsequential between .177, .22, and .25. 

I agree with that premise.  However for it to be possible, the .177 (or the .22) will have to create a wound channel the same size as the .25.  Otherwise the smaller calibers cannot produce as much tissue damage, which is a necessary condition for being able to impart the same energy to the target as the .25.  So in theory that's valid but it isn't very realistic in practice.  

Several reasons why:

1.  It's not easy to drive a smaller caliber to the same energy level as a larger caliber because the air doesn't have as much area to push against to accelerate the projectile.
2. There is the problem of getting the smaller caliber to expand sufficiently to create the same wound channel as the larger caliber.  And if we can use a .22 that mushrooms to a .25, why wouldn't we instead use a .25 that mushrooms to a .30 and be even more effective with a wound channel that is larger still?  
3.  We also still have the problem that pellets which expand well are rarely accurate enough for small game at longer distances.  No problem if the distances are modest but that seems like a pretty significant limitation.

I skinned a gray squirrel my Dad shot with his 177, I do not recall the gun make at the moment. 

Shot it must have been a quartering away shot as entry was in the back of the ribs and I found the pellet just under the skin of her throat.  

If if the picture attached, you will see that there was zero expansion and near zero deformation of the pellet.  Pellets were the Benjamin domes at Walmart.  

The lead ear in the air gun pellets my father and I commonly get are too hard for any real expansion against a soft target.  So I will have to go on the presumption that wound channel is going to outweigh power.  

Power will I’ll be needed for penetration on larger game, that is larger than cotton tails which he has shot many of and are through and through shots.  

Pellets do do not really deliver any hydro static shock like a powder gun bullet does, the velocity is insufficient.  

Power will help get range and penetration, but wound channel and shot placement will win.

What of the necessity of penetrating a harder target?  In my case iguanas.  Some of the larger specimens will have pellets bounce off their skulls at a distance.  Tough, leathery skin is tough.  Would a pellet with a steel point be better?  I have two .22's right now, and don't think moving up in size is the trick.

Yupp, GiveEmLead, I think you’re right..., going up in size increase the area of impact, and thus distributes the force over a larger area, and that might mean it's not enough to break through the skin and/or skull....

I just had a pesting assignment with very hard-to-penetrate skulls.

Here's some thoughs and info I went over before I selected the H&N Baracuda -- because it was more accurate than several of the other options below when I tested them. At a ME of 32FPE and ranges of 20 to 30y, the Baracuda worked great for me (not quite as great on the pests).  

For penetration you might just try a harder pellet.

JSB Exacts are soft. Instead:

Try H&N Baracuda (21.14gr, 0.035BC), or

H&N Sniper Magnum (17.9gr, 0.032BC), or

H&N Hunter Extreme (18.52gr, 0.026BC).

All these have some antimony or other substance mixed in to make them harder (and shinier! ? ).

The hollow points with a metal tip should also be both hard and better penetrating:

JSB Predator Metalmag (17.0gr, 0.028BC),

H&N Hornet (expensive, 16.2gr, 0.024BC),

Crosman Premier Gold Tipped (expensive, 17.4gr).

(The Crosman Premier Destroyer and the H&N Terminator don't have much of a pointy tip, and are more of a hollow point.)

The pellets that are covered in a copper coat are also harder than normal lead:

H&N Field Target Trophy Power (14.66gr, 0.026BC),

H&N Baracuda Power (21.14gr, 0.036BC),

Crosman Premier Copper Magnum (14.4gr, wrongly labled as 15.9gr; 0.023BC),

SIG Zero Point (expensive, 18.06gr),

H&N Rabbit Magnum Power (there are few barrels that seem to like this one, 25.31gr, 0.039BC).

Happy shooting!!

Matthias

My .30 is my go to hunting pellet rifle.

best way i look at it is.. would u rather be hit with a baseball going 20mph or a bowling ball going 20mph ? 

Zippotter,

yes, you're right, if you frame the options like that, the answer is more than obvious..... ?

The energy difference between the two projectiles is immense...!

However, the OP was comparing two projectiles of different calibers — both having the same kinetic energy — not the same speed.... ?

Belly flop feels like hydrostatic shock to me... more about area than velocity.

Much like objects of different weights travel at the same free-fall speed, most guns shoot near the same speed.

Naturally you can expect the fat guys to make a bigger splash.

Does that clear it up? 😉

Edit, forgot to answer the iguanas.

I'd go with Crosman .177  10.5gr domes, aka heavy domes. Head shots are better with solids.

Can anyone recommend another common .177 with better sectional density?

BBs bounce, don't buy those ones!

While I agree with much of the discussion the one thing that I have not seen discussed is how speed and therefor energy affects stability. It is easier to get higher energy in larger calibers without increasing speed. To get a 50 fpe in .177 the speed would destabilize the pellet, but in .25 the speed is well stabilized. I have been Prairie Dog shooting the last two summers and in '18 I primarily used a .22 at 33 fpe and I was successful. This past summer I had a .25 shooting at 50 fpe and much more successful, but both are shooting about the same speed. The .22 was limited to about 80 yards maybe 90 yards, but the .25 is good out to 110 or 120 yards. I believe it was completely due to energy. So we must look beyond the energy and caliber. Another issues that has not been discussed is the impact of cross winds, the higher energy the less impact on higher energy. 

The problen with these discussions (and I have seen/read/participated in quite a few), is that shooters do not understand the mechanics of a lead projectiles when they expand.

It all stems from the bulk of experimentation and documentation been done with jacketed bullets at firearm speeds.

While it is true that there is no hydrostatic shock in a pellet, it also obeys the fact that the stability speed for the diabolo pellet is not that high. Whether you want to believe that it is at 850, 875, or 925 fps is up to you, what is undeniably true is that above 975 fps pellets are unstable in flight and without stability/precision/accuracy there is no killing hit possible (unless it is by sheer chance/luck).

Pellet lead (that is lead with up to 1.5% antimonium) will expand reliably when the IMPACT SPEED  is around 600 to 700 fps, it all depends on the design. Talking of design, the Crosman HP's are NOT expanding pellets, never were, were not designed for that. The dimple is there to expand the head to nominal size, that is why they are reasonably accurate,  but they are NOT expanding pellets under any normal circumstance. Why speed and not energy? because lead is a non-newtonian fluid, and the way lead can  penetrate even steel plates is complicated: Basically you have  "skin" that holds a core that melts with the sudden impact, to then shoot a stream of very hot material through the obstacle.  This is even more evident in the case of jacketed bullets where the skin is a very real gilding metal sheath where the lead is placed.

Solid copper, brass, bronze, or even steel bullets work like nails. They will punch a hole in a steel plate, but the shape and size of the hole will be different.

Now, the other aspect that is barely understood is the concept of energy DUMPED into the target. A large bore, high velocity pellet will pass through and dump a relatively small proportion of its available energy, still, that small proportion could be enough. A smaller, expanding pellet will dump almost all, or all its energy (when the pellet lodges in the target), and that also may be enough. If the target is small, then a small, expanding pellet, or a large pellet at very slow speeds is MUCH more desirable than  the other options. I've used 0.25" cal H&N Spitz Kugeln (25 grs)  at about 16 ft-lbs for pigeons and iguanas, when you can approach them to under 30 yards (that is a Hunt), and it has always been OSOK. Jim Chapman used to have an article about one of my Iguana hunts with a 0.25" cal pump up rifle that took place back in 2009, so more than 10 years ago.

The possibility of a pass-through is much higher therefore with larger bores, and in the context that airgun hunting usually takes place, pass throughs SHOULD be regarded as a no-no. There are exceptions, but it is up to the hunter to hunt and shoot ethically.

Real expanding pellets are usually not accurate beyond the 35-40 yards (Crow Mags), 40-50 yards (BHE and BH), and 45-55 yards (Predator), so shots beyond those distances must better be substantiated with extensive tests by the shooter from the gun he is intending to use.

Lastly, it should be said that, on average: You need 3 ft-lbs to break a mammal's skin, then about 1 ft-lb per inch of penetration in organs, 2 ft-lbs per inch of penetration in muscle. Using a 0.22" pellet, 3 ft-lbs will break most bones (exception being an O'Possum's skull in a raking shot). From there, you need to take into account the aspect ratio of the target to decide what, and how, you are going to use it.

Keep well and shoot straight!

HM

Purely anecdotal observations but a significant sample size and a more apples to apples comparison. Over some years I have of necessity defended a berry garden. The distance, projectile weight, pellet manufacturer, barrel manufacturer, velocity, and FPE are the same, only the caliber was different. I shot about 2000 pest birds (mostly starlings) with a .20 cal JSB 13.4 gr. and another 500 with .177 JSB 13.4 gr. both guns set at 21 fpe. The number of "dropped straight to the ground" vs "fly off then crash" differed greatly. A very noticeable higher number of .20 hits went straight down (almost all of them). The reason more were shot with the .20 was because it became apparently clear in this particular application the .20 was definitely more effective. Both guns were very accurate at placing shots at the 25 yds distance with about a 94% hit rate. Just sharing my observations.

Will,

now THAT is what I call evidence, and convincing evidence! ?

Thanks!

And thank you, Héctor, for explaining some of the finer details! ??

Matthias

The most commonly missed factor when dealing with projectiles designed to deform, is how much of the available energy might be used up deforming the projectile.

From some random low power springer.... .22 soft wadcutter penetrates 1.5" while CPHP penetrates 4".

The only difference is energy wasted deforming the softer pellet, therefore harder pellets must be more efficient in flesh.

I'm getting close to 1000 tree rats with the R9, the stray cat who lives in our yard comes running when she hears the dinner twang.

@nervoustrigger

My At44 shooting hollow point H&N Grizzly will shoot consistent 1 inch groups or less at 100 yards an when they hit at that distance there is still a ton of energy

@benny76 What cal. ? No, I meant the at44. Isn't that a Hatsan ?

Didn't buy it either...just on the basis of area, but at the same energy.

So figured out that I could use 23gr. 5mm (EunJins),21gr. 22's, and 21gr. .25's at nearly the same speed...so about the same energy....so the only real varaible was the diameter.

Pretty much isolated diameter as the only real variable....energy to target was quite close.

Kept energy equal...was still a little plus for diamter,but no where as much as shown on the vids.

"Off switch"hit on game stilldropped them....amiss was still a miss....only the "almost right" shots showed a differcne.
(With the idea that you can't disect what isn't dead....so never will know (reguardless of caliber) whatever might have been hit in a non-vital area and made a get away.)

Kind of a "cheat"...had to slow down the .25 and speed up the 5mm to meet at the same .22's velocity/energy....most folks would just the bigger bore run faster/higher energy....but that would not be a diameter test.

Giving up on "even"...tried the next year with .177,5mm,22, 25 at the same energy. NOT the same velocity,the same energy...so light and fast vs.big and slow,but totaling out about the same energy at short range impact.\

Still a little edge to the big pellet(even though it was pretty slow comapred to the little lite pellet).

So there is somrhing to the area theory....but it'smost noticed when the impact speed/energy is UNEQUAL....which kind of hides the actual efrects of just diameter.

I'll agree with ribbonstone.

A bigger diameter projectile can interact with more tissue on its way through, whereby causing more damage/trauma to that tissue.  

So if a .177 dome and a .22 dome arrive on target with the same energy, the .22 will dissipate more of its energy, both in absolute terms and as a percentage of its total.  More flesh interacted with -> more energy dissipated -> more damage.

However, I suspect there is something to the cavitation channel behind the skirt as it passes through that can close the gap between them to some extent.  Meaning if you stack the deck so the .177 is super light and super fast, and the .22 is heavy and relatively slow, the .177 may produce a sufficiently large cavitation channel as to make it similarly effective as the .22, even if they both were pass-throughs.

I've been reading a lot – and if I understand lethality theory correctly, then....

A projectile (pellet, slug) slices and crushes (destroys!) the quarry’s tissue. The crushed tissue causes a permanent hole, the permanent wound cavity.

Neighboring tissue will stretch briefly and this is called the temporary wound cavity. This stretching usually does not cause any damage. 

What kills – is a permanent HOLE in the quarry – nothing else.

? If the hole is in the brain or spine – the broken brain stops sending signals to the organs and extremities – and therefore the body stops functioning (apart from some muscle reflexes and last-ditch-fight-response) = DRT (dead right there) or VSD (very soon dead).

? If the hole is in the heart, lungs, liver, arteries/veins – the body loses blood or oxigen very rapidly – and therefore the brain doesn't get the necessary oxigen delivered by the blood = DRT or VSD.

? If the hole is other organs or only muscle tissue – the body loses blood – and so the brain will get less oxigen delivered by the blood – F&D (fly & die) or R&D (run & die).

? If the blood loss is minor, the animal might live for quite some time, either to recover or to die from septicaemia/ an infection.

As one can conclude from the above points a bigger hole makes for a bigger blood loss, which makes for a quicker death.

And therefore, a bigger projectile makes a bigger permanent wound cavity assuming both penetrate the same distance, of course, but with our tiny quarry often not too difficult to achieve. Heavy-duty skull bones and thick featherly armor profit from harder lead projectiles (with more antimonium) and pointier projectiles (round nose and pointed, rather than wadcutters).

A "bigger projectile" either means a bigger caliber – or an expanding hollow point. And in order to get expansion, as Hector stated earlier, we need a certain fairly high impact velocity, otherwise expansion is not happening. So, in this instance higher power makes good sense.

❌ A temporary wound cavity does not kill quarry – it just stretches their tissue, but normally doesn't do permanent damage.

❌ The energy dumped into the quarry MUST carry out damaging work, otherwise it’s like dumping it into the dumpster.
That damaging work is crushing tissue. Nothing else kills.
(E.g.: A pellet shot into a bucket of water transfers all its energy to the water – yet it does not damage the water in any way, because moving something that is elastic is not damaging – just like moving elastic tissue to form the temporary wound cavity.)

❌ No hydrostatic shock will kill our quarry... – it is a disputed theory among ballisticians, and all disputing parties agree, it's non-existent below 2,000 fps impact velocity.

What kills – is a permanent HOLE in the quarry – nothing else.

Ah, the fascination with death! ?  

Matthias

#1 killer of any animal .... TRAUMA

sure you can hit vitals, bleed em out, short circuit there fuse box etc .... But the stress's on the body from TRAUMA no matter the source is what shuts an animal down and then the loss of life happens from the wound generally.

 IMO ....

(Photo site is holding my old pictures for ransom...can't get to them.)

You could stop here... I agree,all that dcounts is (1) hitting the good bits inside the critter and (2)tearing things up would get amore immedate reaction.

Same logic would tell me that an icepick stab would kill itin a little bit....but a sword stab would kill it and drop it right there.

But we like hollow points because we're ghoulish and somehow think that splattering something makes it deader than dead.
------------------------------
Years back (on a different site) set up two chronographs....one just ahead of a thin block of ballistic media...one on the far side of the ballistic media....with a soft back stop behind the 2nd chronograph to catch pellets rather than mangle them.

So you'd know the velocity before impact....know the exit velocity after impact... would know how much energy was transfered to the media.

Small game hunter,so like a 3 1/2" block....figuring energy that's not depositied in the block has little to do with critter-killing.

(Feel free to try this....is a simple set up,and you COULD get by with just one chronograph by averaging the impact velocity, then moving the 'graph to the exit side....or use whatever media thickness approximates the cirtter-thickness).

I was partly wrong about that with non-expanding pellets....if it starts with more energy,it deposits more energy even if it has loads of energy left over after exiting the block. So a 35 foot pound RN pellet may exit stillhaving 12 footpounds.....depositing 23 foot pounds....and a 20 foot pound rifle may exit with only 5 foot pounds (depositing 15 foot pounds).

The overall results from non-expanding pellets was pretty much what you expect.

1.The non expanding pellets that are good at not losing velocity in the air (BC) are also good at passing through the test media without depositing as much energy. Pretty direct relationship between BC and energy deposit with non-expanding pellets.

2. Even at the same weight, same speed, bigger does deposit more energy. Think in terms of energy per square inch.

3.SD is a pretty good predictor of penetration....and could consider that as energy transfer per inch of travel and not be far off in energy deposit.

4.The more energy the pellet impacted with, the more it exited with....but also the more it deposited in the media. If 60 foot pound hit only deposits 30% of that energy in the test block, it's still more energy than a 20 foot pound pellet that deposts 70% or a 12footpound hit that deposits 100%.

EXPANDING PELLETS:

Drive any pellet fast enough,hit something hard,and it can expand...or just kind of get mangled.....and depost energy quicker. Normally,accuracy goes bad before you get up to those speeds.

Were not as many HP's then as now...but were some. Even at lower impact speeds,they will tansform into something like a ragged wad-cutter(but not really that"mushroom"type of expansion). At high speeds,will actually expand....some will toss off fragments.

Expadning pellets change shape...but they don't gain weight. So at some point in it's travel,a .22 20gr. expadning pellet is a .30cal 20gr.pancake....basically it dumps energy by transforming into a crappy BC/low SD projectile.

Even better if it tosses fragments...each fragmenet is a really bad BC/SDprojectile, and you've actually made the main chunk shorter/lighter (also a bad BC/SD projectile).

FREAK SHOTS:
Not real sure about some of the freak shots....the ones that didn't take a straight path through the media. Some actually tumbled (not expanded,were stable enough to fly straight in air,got unstable after impact).

The one (newer tests) rifle that would shoot 21gr..`177 piledrivers well showed that impacttumble. Was getting oblong "rips"as exits....thicker media didn't show the increase penetration that SD predicted, so were ruled out for thicker critters. Might work...might not...just added a random factor to be avoided.

Yaw is extremely well documented as a means of generating a superior wound channel with non-expanding bullets.

Decreasing penetration/dumping energy faster....basically doing a HP's job without expansion (at least at airgun speeds).

But airguns (so far) have only done that trick by accident...riding the ragged edge of inflight stability...still,it's an effect worth looking into as it doesn't require hyper-speeds.

Problem being that the wound path is pretty unpredictable.

Ribbonstone,

thank you for sharing your experiments — very interesting setup — and very interesting results! ????

I'm starting to think that effective airgun killing might have four ranges with four different types of projectiles.

I'll share than on a separate thread.... ?

Matthias

It doesn't matter energy if you miss. Go with the caliber/speed that you can make hits the majority of the time.

Soapy.