Thoughts About Penetration

[rsterne]

Well, this cost me a whole day playing with my spreadsheet.... *LOL*.... I spent some time with ChairGun and figured out how the math works for their Penetration calculator.... I then worked out the velocity required to penetrate various distances with a bunch of pellet weights in different calibers.... and graphed the results.... The only factors taken into account by ChairGun are the Velocity and the Sectional Density.... They don't take into account the shape or construction of the bullet.... but if you use the data for comparison purposes (eg. assume a round nosed pellet).... it should provide a decent way to compare calibers.... In simple terms, for a given velocity, a .22 cal takes a 50% heavier pellet to get equal penetration, and a .25 cal takes twice as heavy a pellet, when compared to a .177.... Here are the results.... USE THE VELOCITY AT IMPACT....



The "non-PAL" graph shows the penetration at 450 fps, which I used for the velocity at 20 yards.... It uses an 8 gr. pellet in .177, a 12 gr. in .22, a 17 gr. in .25, and roundballs (44 gr. & 68 gr.) in .30 and .35 cal respectively.... I chose those weights because they are (except in .177) the lightest lead "pellet" available, which should mean the gun would be legal if tested.... Note that the three common calibers all have nearly identical penetration at about 1.75".... I didn't expect that, but there it is....



I haven't assigned likely animal/bird candidates to the various Penetration numbers, as that is so much personal choice.... However, you could do things like say 1.5" is good for mice and sparrows, 3" for crows and rabbits, 5" for Marmots and Racoons, and 8" for Coyotes.... It really is up to the shooter, but I think the relationships between calibers are much easier to understand by using these charts.... For example, to have equal penetration at the same velocity, a .25 cal will require twice the FPE of a .177....



The last set of graphs use the same method, but on big-bores.... I think from what I have read about deer hunting with air rifles, they are actually pretty darn close to what people feel is sufficient for the job.... I would use the 16" chart for deer, and possibly the 12" one for hogs.... but again, that's a very subjective thing.... Moltogordo might want to look at the last chart (24") and give it some thought as he's considering going after a bear with an air rifle....

I'm sure I'll catch some flack over this.... but I don't really care.... I'm just trying to give people another tool to consider when they are wondering what makes sense for different size animals.... and how different calibers compare in terms of penetration.... Your comments are welcome, of course....

Bob

[MustangMike]

nice work bob, it does make sense that a smaller pellet is able to penetrate easier then a pellet of a large size

you never stop to amaze me with ur graphs, and bob i am so sorry you had to spend awhile day playing with spread sheets must have been tourture for you

[rsterne]

I'd particularly interested in comments from the big bore guys.... I think I'll post a link over there....

BTW, it should have been obvious, but the velocity used has to be the VELOCITY AT IMPACT.... otherwise the charts are meaningless....

Bob

[Bullit]

Bob, nice work.  Wish we had it last year during that .177/.22 debate.  I tried to enlarge the charts, but the left side only shows up.  I tried moving it without success.   Am I doing something wrong?

[AirScopes]

why you going to catch flack on this? I think it is awesome work, and valuable!

i'm hoping some people read and understand.

There is penetration, and then there is damage, which might be a lot harder to measure. But I think the relationship between size and penetration makes sense here!

Richard

[Rescue35]

What are we "penetrating"?

Nice info. Once I have some more time I'll relate my experiences with the Dragon Slayer.

[bradyman1]

This is a great graph. However when speaking of penetration it must be noted that (I am assuming here, you know what they say about that) it is not just penetration of soft tissue but more often than not you will be contacting bone. When the bone is encountered the pellet will deform and quite possibly flatten. The flattening of the pellet will cause more resistance greatly reducing your penetration.

I think the graphs are very valuable but I think people should be aware that if you shoot an animal in different spots with the same gun pellet combo you will get different levels of penetration. Angle will also play a large part in the penetration equasion.

I know that you have probably taken this into account, I would just hate to see someone think they can get X" of penetration, take a shot and encouter bone and get a much reduced penetration.

[Plekto]

Also, we have to factor in the mass and the size of the wound channel itself.  Also, the velocity at impact is well below the speed of sound in tissue, in most cases, which means that destructive expansion won't happen either.  Hitting the animal with an air rifle is like hitting it with a tiny little arrow or spear.

Bigger and heavier simply wins at subsonic velocities when it comes to hurting the animal more.  It's why the venerable .45 ACP is still such a great round.  And why, if you watch that video on Youtube comparing a .22 and a .25 Marauder vs squirrels, it's clear which one is doing a better job.   Despite having similar energies at the muzzle.

[bradyman1]

While I agree with Plekto, with out adequate penetration a larger wound channel by itself will not be effective. In some cases a smaller projectile penetrating deeper into the vitals would be more effective than a larger projectile penetrating to a lesser depth therefore not reaching the vitals.

 

[rsterne]

I agree with the comments about how penetration will vary depending on the type of tissue or bone encountered.... and of course on the type of pellet/bullet used.... Any calculation like this has to be an "average" value, and I have no idea how ChairGun determine the value of the constant they use.... I just figured out what it was by working backwards through their results and incorporated it into my spreadsheet.... The really important things governing penetration are the Velocity and the Sectional Density (which in reality is how much mass is pressing on a disc of tissue of bore size to push it out of the way).... No chart such as this can take into account pellet/bullet deformation or tumbling.... all it can do is try and compare what happens with two different bullets that perform in the same way in the same tissue.... That is why I didn't try and label the graphs "squirrel" or "groundhog" etc.... It's up to you to decide the power level you think is suitable based on your experience.... However, if you have a certain degree of success with a given pellet in a given caliber at a given velocity.... these graphs give you the tools to extrapolate to different calibers and/or pellet weights....

It's probably a good idea to choose a "penetration distance" based on what you know will blow right through a specific animal with, say, a roundball or round-nosed pellet.... If you then choose a hollow-point or large meplat in the hopes of retaining more energy inside the animal, then that feature should also extend to similar pellets/bullets on the same graph....

Bob

[Rescue35]

Ok, my Dragon Slayer shooting .495" 178gr roundball at ~650fps (muzzle) managed to penetrate  a White Tail buck and the ball stopped on the far side just under the skin between the membrain and fat. That was at 30 yards.

At 66 yards the same gun and round would only penetrate a log (soft buckeye wood) to a depth of 3/4" yet it would fully penetrate a block of pine 2x4 (1 3/4"). All of the above where not done in any form of scientific manner.

I think the graphs are a great tool for comparison purposes. It is nice to be able to compare X with Y under various situations. One must remember to hunt within your own and your equipment's capability.

[shadow]

Good graph and penatration fall's into shot placement, pellet selection, yardage and we all know if your going foe the fusebox the pellet must traval through some of the toughest bone in the anatomy. Midpowerd springers, .177, 7.9g within the 25yrd range...shot placment is always my first thought. Ed

[Mebits]

Great work, regardless!

[AirHunter4Ever]

BTW, it should have been obvious, but the velocity used has to be the VELOCITY AT IMPACT.... otherwise the charts are meaningless....

That may be difficult to quantify, since the range to the target varies widely in hunting situations.

Perhaps shooting at 5 yard increments, from Point Blank range out to 50 yards, or so, and charting the results ?

Naturally, the risk of shooting the chronograph increases with range.

[rsterne]

Using a program like ChairGun, which contains the Ballistics Coefficient for various pellets, will allow you to input the muzzle velocity and find out what the impact velocity is at various ranges.... It would certainly be good enough for this purpose, as the graphs all show the MINIMUM velocity for each penetration distance.... This is where knowledge of your equipment and situation is vital for every hunter.... ChairGun, in fact, will calculate and show a graph of the penetration at different ranges once you input the pellet and velocity....

Bob

[Bullit]

Good Job Bob!   

[AirHunter4Ever]

Using a program like ChairGun, which contains the Ballistics Coefficient for various pellets, will allow you to input the muzzle velocity and find out what the impact velocity is at various ranges.... It would certainly be good enough for this purpose, as the graphs all show the MINIMUM velocity for each penetration distance.... This is where knowledge of your equipment and situation is vital for every hunter.... ChairGun, in fact, will calculate and show a graph of the penetration at different ranges once you input the pellet and velocity....

Bob

True, but it would not demonstrate the expansion properties of those pellets as velocity decreases. Expansion will affect penetration. Only ballistic testing would show that accurately, IMHO.

[rsterne]

I thought I made it clear that expansion was not covered by the charts.... Your comment was about Chronographing at various ranges and I tried to answer it....

Bob

[AirHunter4Ever]

I thought I made it clear that expansion was not covered by the charts.... Your comment was about Chronographing at various ranges and I tried to answer it....

Bob

Are you saying that penetration will not be altered by expansion and that expansion is not altered by velocity ?

My point is that, since this is the Hunting Gate, expansion is an important factor to consider, since it alters the depth of penetration and it varies with velocity.

I think having more detailed data would be beneficial to hunters, both in terms of penetration and expansion, at various ranges.

[Rescue35]

My point is that, since this is the Hunting Gate, expansion is an important factor to consider, since it alters the depth of penetration and it varies with velocity.

I think having more detailed data would be beneficial to hunters, both in terms of penetration and expansion, at various ranges.

I agree that expansion or deformation is an important factor. The problem lies in the fact that getting the same type of projectile to expand in the same manor every time is difficult. Just like trying to quantify the density of the object being penetrated (which in a hunting situation varies a lot). That makes it difficult to mathematically solve for such a wide range of variables and still have a reliable base line.