Relationship between MV and energy

[Kbhillhunter]

I was wondering if anyone had some good sources that could help me understand the relationship between muzzle velocity and energy downrange (not muzzle energy)

I shoot a rifle with a 20" barrel so I know that the actual MV is likely lower than the factory estimates of the ammunition I shoot. I do plan to Chrono it to get a more accurate reading. But Id like to know how that will effect the downrange energy as well.

Is there a formula or correlation between MV and energy (I'm aware of the ME calculation). The factory loads I use give energy estimates out to 500y so I'm wondering how the actual MV from my rifle would impact those estimates.

 

[Wrench]

It's the same formula. You need to calc your velocity scrub at distance and run the numbers.

 

[BjornF16]

The only thing that really matters is impact velocity and bullet construction. Skip the energy calculation

 

[Crambo]

There are several free ballastic calculators on-line which will allow you to input the specifics of your load (bullet bc, MV, elevation, etc.) that you can determine how the change in velocity impact the energy if this is something you are worried about or want to know.

Any search engine should be able to point you to these.

~ C

 

[Kbhillhunter]

There are several free ballastic calculators on-line which will allow you to input the specifics of your load (bullet bc, MV, elevation, etc.) that you can determine how the change in velocity impact the energy if this is something you are worried about or want to know.

Any search engine should be able to point you to these.

~ C

I see that now. Some of these I've used before but I guess I never looked close enough to realize they had exactly the function what I was asking about. Thanks!

 

[Wrench]

The only thing that really matters is impact velocity and bullet construction. Skip the energy calculation

Read this over and over and over.

If you have the impact velocity to expand the bullet and get desired penetration, you WILL achieve tissue dammage and if that tissue damage is in a blood moving zone of cns....the next step is picking up your critter and notching a tag.

 

[VinoVino]

It’s just kinetic energy, right? Based on the BC of your bullet and how the velocity drops over distance, then just:
1/2 * mass * velocity^2

 

[Anschutz]

Read this over and over and over.

If you have the impact velocity to expand the bullet and get desired penetration, you WILL achieve tissue dammage and if that tissue damage is in a blood moving zone of cns....the next step is picking up your critter and notching a tag.

Yep, find minimum expansion velocity for your bullet, find MV or an estimate using real world drop data, run a ballistics calculator, where velocity goes below expansion is your max range. It'll likely be closer than you think.

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[Aporia]

Not to hijack but is there a publication by the manufacturer or someone like Applied Balliatics that specifies the minimum velocity required for X bullet to expand to at least of 1.0x of caliber diameter?

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[Anschutz]

Not to hijack but is there a publication by the manufacturer or someone like Applied Balliatics that specifies the minimum velocity required for X bullet to expand to at least of 1.0x of caliber diameter?

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Most manufacturers list the minimum expansion velocity or a call to tech support will get the answer.

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[Wrench]

If you have a bullet in mind, there's probably some guys here who can give you their experience on impact velocities too.

 

[762 ULTRAMAGA]

Read this over and over and over.

If you have the impact velocity to expand the bullet and get desired penetration, you WILL achieve tissue dammage and if that tissue damage is in a blood moving zone of cns....the next step is picking up your critter and notching a tag.

This isn't entirely true
There comes a point where a bigger heavier bullet is needed to make quick effective kills, in my experience this occurs somewhere beyond 800 yards depending on specific variables.

For example at 3200' a 110 6mm A tip launched at 3200 fps would get to 1100 yards maintaining the 1800 fps required for reliable expansion. It has about 770 ft lbs of energy remaining
A 212 eldx driven to 3050 will also hit 1100 yards at 1800 fps, and retain 1450 ft lbs of energy.
I think we all know which bullet will be more effective on a big bull, at the range.
You can say ft lbs are irrelevant but it's the product of weight times velocity, so it's a useful metric to be considered.

 

[Wrench]

My experience is that in the 600-800 yard range I've had more bang flops on elk with 140 class 6.5s (SMK, MB, RDF) than I ever have with my 300rum closer.

I'm not sure if it is because the sound is tough to pinpoint, the upset/SD is magic or just dumb luck....but it is absolute.

This is an on and offside scapula of a bull that I killed with an impact velo right around 1800.

Guess how much bullet it took to do this...

There's a point of failure for sure and blood trails favor massive trauma, but to physically kill elk it really doesn't take as much as many think.

I've been fortunate enough to kill multiple elk per year for a long time and this has certainly helped me develop a different confidence than I had 25 or 30 elk ago.

 

[Anschutz]

This isn't entirely true
There comes a point where a bigger heavier bullet is needed to make quick effective kills, in my experience this occurs somewhere beyond 800 yards depending on specific variables.

For example at 3200' a 110 6mm A tip launched at 3200 fps would get to 1100 yards maintaining the 1800 fps required for reliable expansion. It has about 770 ft lbs of energy remaining
A 212 eldx driven to 3050 will also hit 1100 yards at 1800 fps, and retain 1450 ft lbs of energy.
I think we all know which bullet will be more effective on a big bull, at the range.
You can say ft lbs are irrelevant but it's the product of weight times velocity, so it's a useful metric to be considered.

Common sense comes into it as well. I like to use Chuck Hawks Killing Power Formula because it's easy and accounts for Energy, SD, and Frontal Area. In the case you give the 6mm bullet is no good and the 300PRC is good for elk.

The G&S Online Killing Power Formula: Take 2

So while not entirely true, for most cases, using a round that's proper for the game to begin with, you'll be well served using this method in most cases

To fully answer the OPs question. The formula for KE is KE=.5MASSxVELOCITY². So the relationship is when you double weight you double KE but when you double velocity you quadruple KE.

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[BjornF16]

Common sense comes into it as well. I like to use Chuck Hawks Killing Power Formula because it's easy and accounts for Energy, SD, and Frontal Area. In the case you give the 6mm bullet is no good and the 300PRC is good for elk.

The G&S Online Killing Power Formula: Take 2

So while not entirely true, for most cases, using a round that's proper for the game to begin with, you'll be well served using this method in most cases

To fully answer the OPs question. The formula for KE is KE=.5MASSxVELOCITY². So the relationship is when you double weight you double KE but when you double velocity you quadruple KE.

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Completely disagree.

That formula doesn’t account for FMJ vs Bonded vs mono vs cup and core.

What matters is the specific bullet and it’s minimum velocity for effective expansion in game.

This isn't entirely true
There comes a point where a bigger heavier bullet is needed to make quick effective kills, in my experience this occurs somewhere beyond 800 yards depending on specific variables.

For example at 3200' a 110 6mm A tip launched at 3200 fps would get to 1100 yards maintaining the 1800 fps required for reliable expansion. It has about 770 ft lbs of energy remaining
A 212 eldx driven to 3050 will also hit 1100 yards at 1800 fps, and retain 1450 ft lbs of energy.
I think we all know which bullet will be more effective on a big bull, at the range.
You can say ft lbs are irrelevant but it's the product of weight times velocity, so it's a useful metric to be considered.

Meh…I would argue 1800 fps is too low for the a-tip. I haven’t heard many good things about the a-tip at slower speeds. (and it’s half of mass x velocity x velocity)

 

[TheGDog]

Well... the projectile has a B.C.
And we know that the effects of the B.C. ... and drop in Velocity at a certain distance will start to make the trajectory path dip at a more exponential / increasing rate.

So... when you start off with even less velocity to begin with... it can only result in that point where the trajectory starts falling off fast... to begin a little bit earlier, in terms of distance of the bullet in flight.

 

[762 ULTRAMAGA]

My experience is that in the 600-800 yard range I've had more bang flops on elk with 140 class 6.5s (SMK, MB, RDF) than I ever have with my 300rum closer.

I'm not sure if it is because the sound is tough to pinpoint, the upset/SD is magic or just dumb luck....but it is absolute.

This is an on and offside scapula of a bull that I killed with an impact velo right around 1800.

GuessView attachment 383065 how much bullet it took to do this...

There's a point of failure for sure and blood trails favor massive trauma, but to physically kill elk it really doesn't take as much as many think.

I've been fortunate enough to kill multiple elk per year for a long time and this has certainly helped me develop a different confidence than I had 25 or 30 elk ago.

I hear you in the 600 to maybe 800 range.
My wife and I kill several bulls a year as well, for awhile I was on a 6.5 saum kick and killed a bunch of bulls out to 940 with 147's.
The 940 yard bull was stretching it way to far, and really changed my opinion of killing long range with small calibers/ light bullets.
Basically I hit him dead center in the lungs, I found him an hour later bedded and he almost made his feet before I put him down.
The bullet expanded perfect but there just wasn't enough energy to cause a good wound channel, whereas inside 600 yards that combo put hooves in the air

 

[Anschutz]

Completely disagree.

That formula doesn’t account for FMJ vs Bonded vs mono vs cup and core.

What matters is the specific bullet and it’s minimum velocity for effective expansion in game.

Meh…I would argue 1800 fps is too low for the a-tip. I haven’t heard many good things about the a-tip at slower speeds. (and it’s half of mass x velocity x velocity)

No formula takes that into account that I'm aware of. Formulas are good for making apples to apples comparisons (TTSX vs TTSX) but at the end of the day, all of us choose the bullets, rifles, cartridges, etc. we use on game and have to live with the consequences of their effectiveness whether good or bad.

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[Kbhillhunter]

No formula takes that into account that I'm aware of. Formulas are good for making apples to apples comparisons (TTSX vs TTSX) but at the end of the day, all of us choose the bullets, rifles, cartridges, etc. we use on game and have to live with the consequences of their effectiveness whether good or bad.

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I've been looking into MPBR and I was curious what would be the most limiting factor, target diameter, MV, or ME. Definitely will be target diameter for what I shoot. MV is still inside the effectiveness range for the bullet and energy is still >1500, though it sounds like I should have been placing more importance on terminal velocity.

Either way this has all been enlightening.