PaulS wrote:

OGW (Optimum Game Weight) formula that one of the big name shooters (I'd have to look up his name again) came up with. I especially like it because it closely matches my own formula that was derived from measurements, penetration tests, and expansion tests that I did myself. Factors included are the weight of the bullet, velocity, diameter, dynamic decelleration and expansion/upset. It is all converted to numbers and ratios and while it is not perfect for every bullet design it is the best system I have ever found.

This sounds very interesting, and also an accurate way to estimate bullet performance. I'd like to hear more. Where do you get (or estimate) the deceleration? Is this a value for deceleration after penetration of the game animal?

For now, I'll stick with being "overgunned" and using careful shot placement to make sure the deer drops where he stands. On public lands around here, if an animal runs for any distance it is likely to get riddled with holes.

OGW is an Ed Matunas thing and looks pretty reasonable. Looking at the info (Lyman's Guide to Big Game Cartridges and Rifles) I think it would be better called "Maximum Game Weight". It doesn't really take into account the various bullet types, just specifies "big game expanding bullets".

OGW = V^3 x B^2 x (1.5 x 10^-12) where V is velocity and B is bullet weight.

For a varmint bullet use (5 x 10^-13)

Pumpkinslinger wrote:

OGW is an Ed Matunas thing and looks pretty reasonable. OGW = V^3 x B^2 x (1.5 x 10^-12) where V is velocity and B is bullet weight. For a varmint bullet use (5 x 10^-13)

Units? I am guessing V is in feet/sec and B is grains. That would make the term in parentheses a conversion factor to result in pounds ( with units like: sec^3 pounds / feet^3 grains^2 )

This discussion is starting to get interesting..

Always loved math formulas when discussing shooting stuff..
Math don't lie and results are repeat-able.

To me it looks like it is nothing more than an energy conversion !!!
Bullet weight times velocity ='s Foot Pounds of energy.
X amount of energy required for animal weighing X amount.

Although energy is important it's only part of the equation.

It's been proven that how a bullet reacts when it hits something is the most important part. Ballistic coefficients, sectional density, energy and velocity are meaningless if the bullet isn't capable of creating a permanent cavity through the vitals.

gelan, just for you but you probably already know this one !!!

Energy in foot pounds = WV^2 / 450400
W= weight in grains
V=velocity in feet per second


Here's another way to look at it !!!

All 30 caliber 180gr bullets have a sectional density of .271 regardless their overall length or profile. If we were to propel them at the same velocity their calculated energy would all be the same. But if we were to shoot them into ballistic gelatin we would see results ranging from limited penetration to complete pass through. We would also see wound cavities that vary in size and shape. If we were to take it a step further by placing a harder media to simulate bone in front of it we would see yet another set of results.

So with this understanding it's easier to understand why a smaller caliber with less weight may actually perform better than that of a much larger size.
So once again it comes down to one simple fact; It's not the size of the bullet........It's what it's capable of doing !!!

chambered221 wrote:

So with this understanding it's easier to understand why a smaller caliber with less weight may actually perform better than that of a much larger size.

Then there is ballistic coefficent where a bullet that is more aerodynamic will maintain its velocity better down range and makes the terminal results all that much more interesting. Find a good bullet with a high BC and your can improve your capability to reach out (if the wind doesn't complicate things too much).

Marty, yep, ft/sec and grains.

My formula is just a little different than Ed's (I think) though the resulting numbers are very close. If you consider the mass of an object and the mass of a projectile there is a correlation between the velocity of impact (adding the factor of average decelleration) and the damage done. Penetration is a function of form, velocity, weight and strength but you only have to penetrate through the vitals of an animal to kill it. A high velocity 22 caliber bullet can kill an elephant if you shoot it into the brain through an eye socket. These calculations are not based on shots like that. My calculations and Ed's are for shots into the heart and lung area of big game animals. Reduced to the simplest terms my formula is momentum (in foot pound/seconds) times the energy (in foot pounds) (at the point of impact - not at the muzzle) divided by 2xx (not an exact number but I don't remember the exact number off hand) and the answer is the maximum number of pounds your animal should be close to for a one shot well placed kill.
The 2xx (215?) number is a complex multiplication and division of the constants involved in the equation - it is always the same calculation because the density of the body, decelleration and energy transfer rate is always the same. (or the average is at least close)

I do not believe that these formulas are the end-all of trying to find an acceptable answer to the question of what round should be used on what size game but they are two of the best that I have seen. They give easy to understand data that closely aproximates good choices for bullet and game size.

chambered221 wrote:

gelan, just for you but you probably already know this one !!!

Always happy to learn anything, even if it is revisions.

I understand the hydrostatic shock supersonic projectiles imparted onto flesh on impact.
The shock enough to force blood vessels to literally explode and saturate the surrounding flesh with blood (dark damaged flesh on the path of the projectile).

So what about SUBSONIC caliber?
My Whisper is using 195 gr cast boolits (Lee 309-200) with MV of 1050fps.
On almost every case (20+ goats and pigs), I get a tiny 30 cal entry hole and sideways wide exit hole that looks like knife/ arrow wound.
Here, we are talking about 500 - 600 foot pound of energy, yet, fortunately due to correct placement of shot, so far I have not lost any.

Love to throw a curved ball

PaulS wrote:

I do not believe that these formulas are the end-all of trying to find an acceptable answer to the question of what round should be used on what size game but they are two of the best that I have seen. They give easy to understand data that closely aproximates good choices for bullet and game size.

I agree 100%. No formula can give you an ironclad answer for how a given load/bullet will work on game because there are too many other variables. These formulas do give us a way to do a basic comparison of loads and provide endless arguments about which is "better".

Gelan, your load gives us:

477 ftlbs of energy at the muzzle

OGW of 66

Taylor KO of 9

Sounds like your bullet is yawing in the target but has enough oomph to keep going.

Slim, here again BC is only part of the equation !!!

A Barnes .30 caliber 180gr TSX has a BC of .450, if it were launched at 3000fps (near top end for 300WSM) it would be doing about 1850fps at 600 yards with 1368 ft. lbs. of energy.
A 150gr .277 Nosler Ballistic Tip has a BC of .496 (one of the highest BC's available for a .277) it would require a velocity of approximately 3150 fps (close to tops for a Weatherby mag) to reach the energy potential of the 180gr bullet.
The 150 would reach the 600 yard target with about 7 inches less in drop.

If I were hunting long range elk or moose the high BC and 7 inches less drop would be meaningless to me in this situation, I would opt for the Barnes bullet without question !!!

You could also turn this around at take a look at it another way.
The .30 cal 180gr Nosler Ballistic Tip carries a BC of .507. I would happily trade that for a .450-.475 BC of a Partition, TSX, or premium bonded bullet in .284 diameter at magnum velocities.

It may sound as if I'm picking on B-Tips but the fact of the matter is I think they're one of the best small to medium sized game bullets ever made !!!

Choosing the proper bullet shouldn't be based on a set of numbers alone. Today it seems as if hunters are more worried about what looks good on paper than actual field performance. As an ethical hunter I'm more worried about a clean one shot kill than I am about getting a bullet to a target X amount inches flatter, how small of a group I can shoot or how much wind bucking capability I have.

Just pointing out another reason why some smaller caliber bullets with high BCs can do better than larger caliber bullets. That's why a 6.5mm caliber often does better than a .30 cal at range.

Hydrostatic shock causes "bruising". Thats what shattered blood vessels are. In a small area around the bullet path and typically within 7 inches of the entry point it can cause real damage but not as much damage as a bullet breaking bones and cutting vital tissues. The only place where hydrostatic shock kils is when the central nervous system interupts the signal to the heart and lungs. (like severing the spinal cord or exploding the brain) Mosy hunters will experience that kind of shot only accidentally.

I love the energy comparisons between bullets.
If you get a 5 grain sewing needle going fast enough it can have the same energy as a 2000 fps 180 grain bullet. On hitting an animal the sewing needle may even penetrate farther that the bullet but it will do very little damage compared to the bullet. Why? The needle would be travelling at hypersonic speeds and hydrostatic shock would certainly be present. The two things that the needle has less of is momentum and diameter. These two factors are at least as important as velocity when it comes to killing an animal. Bullet upset, whether it is expansion or tipping, causes damage (cutting and tearing) to tissue than any amount of "hydrostatic shock".