3 Different Cartridges, Same Weight & Velocity Terminal Performance

[MagnumManiac]

Sectional density is a great indicator of penetration, yet, it does not take bullet construction into consideration. This is what I alluded to earlier.
For example, all .338" 250g bullets have a SD of .313, but the construction of said bullets will change the amount of penetration.
If we take this and compare with a .375" 250g bullet SD of .254, the outcome will favour the .338", yet bullet construction can, and does trump this. Even if we step up to a heavier bullet in the .375", like a 270g, it is uncertain that it's SD of .274 is going to do much over the .338", if we compare a bonded bullet of the same construction.

Cheers.

 

[MagnumManiac]

True - but which will have better terminal performance, is the question.

The 25 cal would have the better SD, so all else being equal, it would be the better penetrator.
I have numerous examples for you. I have hunted with 6.5mm bullets for a long time, and 25 cal, in most instances where velocity is similar, the 6.5mm wins because it is another step up in weight slightly, however, bullet construction plays as a big a role in penetration as does SD. An example, a 115g Partition fired at 3267fps out penetrates a 120g Partition at 3030fps from a 25-06 99% of the time, so even velocity differences play a role here. SD is not the be all, end all…

Cheers.

 

[fordy]

Gday Kris

@fordy
This is right up your neck of the woods discussion.

Kris

A interesting question that has many answers

The first one I'll ask to give us a little clearer on the penertration requirements needed should be known first before any clearer assumptions be made



So we need to know the answer to my question first as if 20 inches of required penetration is required & if all 3 will exceed that penetration capabilities we need to understand how much ea pill will as now we are looking @ where the pill sits in the charts of width of wound channel per caliber & length of wound not just total penetration capabilities

Briefly /broadly
bigger the meplat the wider the wound
the smaller meplat the greater penetration

Sectional density is one that has stood up well in days gone by , today it's only just getting into the depths of breaking it down further/ better & more into length x calibre ratio in flight & terminal form of length of pill x calibre in terminal state

Then depending on the frontal diameter the shape of that frontal diameter & FOC of this terminal pill we have the true answers of what that pill does then add rpm to the equation & it shifts again
Velocity was once you can walk through water but not run
Meaning a slower pill will out penertrate a faster & yes it still holds water today for those pills of that era but some of today's pills not as much to not @all

Sorry I can't give a more precise answer as if we are talking a frangible a bonded a mushroom mono or a shedding mono they all have different characteristics that will lead us to having a different outcome on the 3 different calibers regardless if it is MV or impact as those factors need to be known first

Done a little on this lately & still trying to gather drone videos to show more visuals of what meplat size does but man alive it is hard to get a normal video camera the drone the shooter all lined up on the critter @ the same time then the critter moves hmmmits frustrating & I've got to get my son on the drone as man he's good @ flying it & battery life of my drone is 38 /47min in various conditions so we don't have enough time ( my mate & I ) for we are novices

This drone has a good thermal on it & that is cool on showing patterns also on pill behaviour
So if I can get the stars to align in a better way than we are getting @ the moment some cool information will come out of it im sure
Cheers