Applied Ballistic terms/concepts in action?

[fmajor]

OK, I commented on the "7mm-300win thoughts" thread, but realized my post was indeed more a derail than a contribution to the discussion at hand...

Since I couldn't later delete/re-compose I thought to start a thread to *hopefully* generate some meaningful, well-thought-out dialogue about something we long-range hunters/shooters often argue about:

What or How can we determine/predict the ability of a projectile to maintain it's inertia as it passes through our intended media (large game animals)

Are the keys to the solution of my question as simple as initial velocity, projectile weight, projectile diameter/caliber, ballistic coefficient and sectional density? Are there other variables to determine?

I'm all for 7mm's (the 7mm/300 Win will be my next build) and a strong proponent for long range hunting, but to me the thing that's tough to get to is retained inertia and/or a projectiles ability to resist inertia degradation.

What I'm thinking of is not simply retained energy; Rather, a projectiles ability to continue penetrating through heavy, energy sapping material.

What is the most important projectile variable to consider? Of those I cited above (initial velocity, projectile weight, projectile diameter/caliber, ballistic coefficient and sectional density) is there one, single-most important variable?

For example, imagine a poorly hit/angling away elk with a full stomach of ground up, moist grass/hay at (for the sake of illustration) 1,400-1,500yds. What's it gonna take for a projectile to blast through all that?

So, for the sake of discussion, say a 60gr 220 Swift bullet at MV ~4,000fps may be able to break a rib bone just under a large animals hide at 500yds, but it may not penetrate all the way through the body cavity whereas a 1,570gr 20mm Vulcan bullet at ~3,400 fps would be able to not just break the bone, but would have enough retained inertia to continue on through the animal in the conditions set above (much like the angling away elk shot example above).

So really, the question is how much energy/BC/velocity/etc is needed to ensure a projectile could slam through the entire length of a large elk to unquestionably destroy vital organs and create a significant wound channel? Sure, a 20mm Vulcan round would undoubtedly accomplish that, but otherwise how much is actually needed?

Retained energy at the point of strike/impact is one thing and has a "simpler" mathematic path derived from initial velocity, projectile weight, projectile diameter/caliber, projectile twist rate, BC (which is comprised of diameter/weight/drag coefficient, etc) and probably a few other variables I've forgotten. But I don't think that's all there is to the "penetration puzzle".

However, calculating how much inertia a given projectile will loose (in a given medium) is (for my simple mind) more elusive to calculate. I've read on this topic for a few decades so it's not a flippant question/topic, but since I'm not a mathematician/ballistician I simply don't have the necessary tools to begin to arrive at a solution.

Ideas? Opinions? Thoughts?

Am I over-thinking this?

 

[FearNoWind]

...
Ideas? Opinions? Thoughts?

Am I over-thinking this?

Yes, I believe you're over thinking this. The variables involved in trying to work out a constant that can be applied to every hunting situation are endless. Besides a belly full of grass (which implies a gut shot - not a pretty thing to witness and it ruins a lot of meat) there are bony structures, sinew, varying muscle densities and other factors which would take enough time to calculate that the intended target would die of old age before the shooter developed a solution which would, at best, be nothing more than an estimate.
For hunting, I try to focus on remaining energy at distance to target on a well placed shot using a bullet that has good expansion characteristics and not worry about things as complicated as measuring the boundaries of the universe.

 

[fmajor]

Thanks for your comments!!!!

Yes, I believe you're over thinking this.

Ha ha - yeah, with things/subjects I think are important I tend to analyze A LOT!!! Sometimes to a fault.....

The variables involved in trying to work out a constant that can be applied to every hunting situation are endless.

And that's why we see sooooo many discussions about whether so-called "marginal chamberings" (vis a vis 270 Win, etc) are "potent enough" to be adequate for elk hunting. Proper shot placement being the primary criteria assumed as the constant in those arguments.

Besides a belly full of grass (which implies a gut shot - not a pretty thing to witness and it ruins a lot of meat) there are bony structures, sinew, varying muscle densities and other factors which would take enough time to calculate that the intended target would die of old age before the shooter developed a solution which would, at best, be nothing more than an estimate.

I was more thinking of making the calc's/determination of projectile/caliber/velocity at the loading bench (or ammunition counter) not something required in the field.

For hunting, I try to focus on remaining energy at distance to target on a well placed shot using a bullet that has good expansion characteristics and not worry about things as complicated as measuring the boundaries of the universe.

And that's where we are currently with calculating retained energy at a specific distance.

I guess I'm trying to think through a scenario which is populated with too many variables to account for....

I wonder if Sectional Density + Retained Energy + ????? could provide a better "in-field/on-target" performance value?
- just kidding..... ;-)

 

[CoasttoCoast]

In all honesty, there isn't 1 single aspect that contributes to a bullets effectiveness. Everything you listed does effect energy down range. Muzzle speed, BC, bullet weight, ect all effect how much energy a bullet carries upon its back.

I think Bullet construction plays a big part with the transfer of energy. there are bullets that are designed to fragment upon impact, while others are made to penetrate. I prefer to use a bullet that is somewhere in the middle (nosler accubond). It retains enough weight to be effective, yet it penetrates through hide and bone pretty good.

I do think your overthinking this. If you choose a good bullet, that penetrates well, transfers energy into the target, and shoots well out of your gun your set. I assume you hand load, so you can take most of the variable out of the equation that is associated with factory ammo inconsistencies. Run your charts and go have fun!

 

[cummin_un_glued]

In all honesty, there isn't 1 single aspect that contributes to a bullets effectiveness. Everything you listed does effect energy down range. Muzzle speed, BC, bullet weight, ect all effect how much energy a bullet carries upon its back.

I think Bullet construction plays a big part with the transfer of energy. there are bullets that are designed to fragment upon impact, while others are made to penetrate. I prefer to use a bullet that is somewhere in the middle (nosler accubond). It retains enough weight to be effective, yet it penetrates through hide and bone pretty good.

I do think your overthinking this. If you choose a good bullet, that penetrates well, transfers energy into the target, and shoots well out of your gun your set. I assume you hand load, so you can take most of the variable out of the equation that is associated with factory ammo inconsistencies. Run your charts and go have fun!

^^^^ this! I feel that the single most important aspect of what your asking about would be the projectile's construction. a 7mm 160gr nosler ballistic tip isn't going to perform the same as a 160gr accubond even with BC and every other variable being the same. Now throw something like a 160 barnes TSX into the mix because the BC is very close yet the solid copper construction is going to cause it to have a much higher minimum velocity. Same with hornady bullets. in 7mm they make 3 versions of a very very similar looking bullet that could be considered a long range bullet. They have a 162gr SST a 162gr Interbond and a 162 Amax.