Caliber or Power
I've been watching a lot of videos where there’s a common graphic about the difference in calibers. The effectiveness of a .25 caliber round over the .22 caliber pellet as a hunting round seems to be attributed to the 50% increase in area.
I don’t really buy this. To me it seems more likely that the heavier and slower moving pellet is dumping more energy into the target because it has....more energy to dump.
I assert that if I shot a squirrel with a .22 caliber bullet/pellet weighing 30 grains and a .25 caliber bullet/pellet weighing in at 25 grains and they deliver the same energy to the target, the caliber difference will be deminimis in the “knockdown” equation.
Knockdown is more a function of energy delivered to target, how one gets there is less important
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.
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).
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!
There you have it, the world according to John.
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!
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.
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.
There you have it, the world according to John.