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Discussion Starter · #1 ·
Hello Everyone,

I'm back with yet another newbie question (one of these days I promise I'll stop).

Can someone explain in simple terms what velocity vs. energy do for bullets?

I know bigger bullets make bigger holes, and bullets with higher muzzle velocities move faster than ones with lower velocities, but how does this translate to bullet performance?

Is velocity related to penetration? Is energy related to "damage" once the bullet penetrates?

What is prefereble? A heavier slower bullet, or a faster lighter one? (same caliber)

The reason I ask is because I'm getting ready to buy a bunch of ammo, (in 45 ACP) for my XD45c and I have noticed that there are anywhere from 165 grain with high velocities to 230 grain ones with lower velocities.

Thanks for the help. Any links or extra reference readings will also be appreciated.

Merry Christmas, and Happy Holidays to everyone,

Leprechaun97
 

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There's no real simple answer. There's a lot of physics going on. Velocity and acceleration have part to do with it. As does bullet design and weight.

.22LR 40gr LN - 1080ft/s - 104 ft·lbs
.22LR 38gr LN - 1260ft/s - 134 ft·lbs
.22LR 31gr LN - 1430ft/s - 141 ft·lbs

.45ACP 165gr Federal Premium Low Recoil JHP - 1,060 ft/s - 412 ft·lbs
.45ACP 185gr Speer Gold Dot JHP - 1,050 ft/s - 435 ft·lbs
.45ACP 200gr Speer Gold Dot JHP +P - 1,080 ft/s - 518 ft·lbs
.45ACP 230gr Speer Lawman FMJ - 830 ft/s - 352 ft·lbs

.308 Winchester 165 gr BTSP - 2,700 ft/s - 2,671 ft·lbs
.308 Winchester 168 gr BTHP - 2,650 ft/s - 2,619 ft·lbs
.308 Winchester 175 gr BTHP - 2,600 ft/s - 2,627 ft·lbs

.308 NATO 146.6 gr 2,756 - ft/s - 2,472 ft·lbs

Lets look at a .22LR vs a .45ACP
Even though the .22LR is faster, the mass of the bullet does not match the mass of the .45ACP. Faster does not necessarily mean better.


Now let’s look at a .45ACP FMJ vs .45ACP HP
The design of the hollow point bullet allows for faster total transfer of energy into the target. (Ideally, you would compare equal velocities, but I don't have numbers on hand for that.) Expansion of the bullet allows more transfer of energy sooner. If there was too much velocity behind the bullet, it may not expand fully and not transfer as much energy to the target.


Finally lets look at .308 Winchester vs .45ACP
The .308 has velocity and mass. Depending on the thickness of the target, total transfer of energy may not occur and the bullet may pass through the target.


So... There's going to be a sweet spot for each caliber that will allow 100% transfer of energy from the bullet into a specific target. It's unfair to compare different bullet designs and different calibers. If you really want the math we can go over that too.

If you're buying factory ammunition, the manufacturer should have, on their website list of energy @ distance for you to compare. I suggest you checking that out.

Hardwarz
 

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Discussion Starter · #3 ·
Thanks Hardwarz. I appreciate the information.

What I'm trying to figure out is how to understand the information published on the websites so I can compare/decide which bullets to purchase.

I'm not trying to compare different calibers since I am very happy with my .45ACP. What I'm trying to determine/understand is what differences exist between the different weight of .45's.

For example: all else being equal, why would anyone buy a 165 grain bullet (in .45ACP) vs. the 200 or 230 grain?

Same goes for the +P loads in .45, especially if they're being fired out of a 4" barrel.

I've heard that lighter bullets offer less recoil and are faster, but I don't understand what this would translate to once the bullet hits its target, more specifically at self defense distances, probably not further than 25 yds.
 

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For example: all else being equal, why would anyone buy a 165 grain bullet (in .45ACP) vs. the 200 or 230 grain?
Over simplification... "for every action there is an equal and oppsite reaction." Smaller grain bullet = less powder to push the smaller mass the same velocity as a larger grain bullet. This will mean less recoil for the shooter

Same goes for the +P loads in .45, especially if they're being fired out of a 4" barrel.

I've heard that lighter bullets offer less recoil and are faster, but I don't understand what this would translate to once the bullet hits its target, more specifically at self defense distances, probably not further than 25 yds.
Over simplication again.... "F=MA"

This means Force = Mass x Acceleration. They are all depended upon each other. If mass is reduced then force is less. Then again, bullet design (Hollow Point) may compensate for part of the loss by expanding and allowing faster transfer of energy to the target.

Ideally, you want as much of the force to dissapate into the target in the shortest amount of time.

Hardwarz
 

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It all comes down to bullet performance, expansion and penetration.

Energy transfer in and of it's self does not do any damage to the target.It helps expand the bullet. For example a bullet with X foot pounds of energy, will not wound better than a bullet with 100 foot pounds less energy via energy transfer to the tissue. Energy transfer is not a wounding mechanism. The much stated "dumping all it's energy on a bad guy" statement is not correct. The energy transferred into a target is not significant enough to damage tissue via temporary cavity. Temporary cavity is the stretch cavity created by the fast moving bullet hitting a target. It's the big hole created in clay, or what makes watermelons, and water jugs explode when shot. The thing is human tissue is very elastic, it will stretch and not tear so there will be no damage. The energy transfered to the bag guy is similar to the recoil the shooter feels.

Heavier bullets tend to have more momentum thus push through barriers such as heavy clothing, and bone, better than lighter bullets. Heavier bullets tend to penetrate deeper once they expand.
 

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My best advice is to not overthink your ammo purchases. If you are buying ammo from a reputable manufacturer (no exotics) and are shooting out of a "normal" style handgun (something with a 2" barrel or longer) you will find anything you purchase to be sufficient. Yes, doing a ton of research and finding the cartridge that gives you the best energy/penetration/expansion, but it won't be much better then rest of the offerings.

For example (and I'm pulling these numbers from nowhere, so don't quote me) the Federal HST in .45 ACP at standard pressures with a weight of 230gr might give you 450 ft lbs of energy. Say it penetrates 12" in gel, and expands to .75". Then you might find Cor Bon DPX in the same caliber but only 165gr. It will penetrate 11" in gel, delivers 500 ft lbs of energy and expands to .80".

All in all the differences between both those cartridges will be minimal at best. They'll both get the job done equally. Yes, the scale might be tipped towards one or the other, however the difference in performance is negligable. Both are top-notch cartridges with good bullets designed to expand well and delivery their energy inside the target.

You should base ammo decisions on how accurately it shoots (not all ammo shoots POA), the recoil, and cost. You will want to practice with your carry ammo, so don't buy something you can't afford to shoot.

Hopefully that makes your decision a little easier.
 

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For example: all else being equal, why would anyone buy a 165 grain bullet (in .45ACP) vs. the 200 or 230 grain?
Well mostly because someone wants to.

A bullets energy is the product of its mass times it's velocity squared (Remember E=MC2 ?)

A bullets momentum is just it's mass times it's velocity.

So a lighter bullet at a higher velocity will have more kinetic energy.

Folks have been arguing small light high energy projetile vs bigger, heavier, high momentum projectile since the first cavemen started throwing rocks. That argument won't end until we get some decent manportable directed energy weapons like lasers, phasers or particle beams.

20 years ago you needed higher velocity to get JHP bullets to expand. Now days with more modern bullet designs the slower bullets expand pretty well. Bullet design is more important that the numbers published on a ballistics table. The only way to understand how bullet design effect your choice is to test it in a relaible, repeatable media. (I use Simtest)

Some folks think that that only way to stop a threat is to drive a big bullet all the way through it and wait for it to bleed out. Others think that the energy from the bullet, if high enough, can be transferred through the body to the brain and stop the threat quicker. This is often referred to as Hydrostatic Shock or Ballsitic Pressure Wave.

From my personal observations of over 32 years of deer hunting, 25 of that with handguns, I think that HS or BPW effects are real, but they don't always work.

So I prefer a bullet that penetrates deep enough to make my target bleed out, but at the same time I want as high of energy as possible.

In short there is no simple answer. But if you are confused about what defensive bullets to choose, I always recomend a middle weight for caliber, premium JHP from a major manufacture. Make sure it is 100% reliable in your gun. Train to place your shots well, because your ability to place shots will matter a whole lot more than the brand of bullet in your gun.
 

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Here's the basic idea.

Newton's laws state that an object in motion tends to stay in motion and that for every action there is an equal and opposite reaction. Basic physics tells us that mass * velocity squared = energy.

Based on that information alone we can conclude that in order for a bullet to penetrate deeply it needs at least one of two things, mass or velocity.

You can move a light bullet very fast or a heavy bullet much slower with the same amount of powder. The lighter bullet will likely have a much higher energy number, but that is no guarantee of adequate penetration.

The other factor (this is the tricky one) is what happens with Newton's third law (For every action there is an equal and opposite reaction.) both when you fire the gun and when the bullet impacts the body.

When you fire the gun a lighter bullet will have less felt recoil than a heavier bullet if the powder charge is the same in both rounds. If you increase the powder charge to keep velocity constant between the two bullet weights it drastically increases the forces exerted on the gun and may be unsafe.

When the bullet strikes the body it will begin to slow down and the rate at which it slows down is directly related to velocity and bullet design. If both the light and heavy bullet have the same design and dimensions the lighter bullet will slow down faster. It is also more likely to be deflected by things like bones and objects in pockets. Heavier bullets, though slower, often penetrate better because they are less likely to be deflected and they maintain velocity longer.

Now that you know all that theory, you are probably no close to deciding which is better between heavy and light bullets. The only real way to know if a particular bullet/powder charge combination works well is to do testing. Since you probably don't have the time or money to test every brand and weight of ammo out there, you need to investigate testing done by others.

With a .45ACP you will probably find that heavier rounds are better penetrators and are more prevalent with law enforcement agencies.

I hope that helps.
 

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Discussion Starter · #9 ·
Thanks guys. I appreciate all y'alls time in trying to educate a fellow member.

Well, looks like I'll be going to range a bit more before the end of the year. I don't mind the testing at all, but now I have a bit more info to go on.
 

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All valid points & you can over think this light vs heavy to death. Energy is only relavent if the bullet can do work. A 230grFMJ & 230grJHP have the same energy if they have the same vel. The FMJ will likely penetrate the target & the bullet does little transfer of enrgy. Not that energy transfer is that important, but some is better than none. A heavier bullet has the potential to expand to a larger dia. & still penetrate deep. Feed your pistol any decent 185gr (short bbl 45s) to 230gr JHP & you will be fine. I'm not a big fan of +p ammo, too much recoil for the slight 50fps gain, especially in smaller pistols.
 

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Simple answer: research this stuff in books that start from the beginning.

Someone must have good references, you can usually buy them used on Amazon.com or sometimes find them in the public library system.

It's actually very interesting to see the differences between Scientific Fact and Lore.

nothing personal to anyone.
 

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Books Dr. Martin Fackler, Dr. Gary Roberts to name a few good references. Articles posted by IWB, firearmstactical.com will have many good articles along with a good list of books.
 

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Also remember that what happens to a bullet in a real life self defense scenario is a very dynamic thing. As stated before, things like bone, harder tissue, softer tissue, objects in pockets, thickness and type of clothing, ambient outside temperature all play a role in the final outcome. It would be impossible to create a test scenario for every possible combination so you will never truly know exactly how your choice of ammo will work in all situations.

The best thing to do is some ballistics testing research and choose several types of ammo you find to have the results you like. Buy two or three boxes of each and shoot them through the weapon you will be carrying for defensive purposes and, from those, choose the one you find to be the most accurate and reliable as to feeding and firing.

Once you have chosen your carry ammo, practice practice and practice some more for good shot placement. Placement will be the number one contributing factor to your survival in a self defense situation where you have to pull the trigger.

And one last note . . . .
Absolutely NO AMMO on the market to day that is sold to the public has the ability to "knock" anyone down. It doesn't happen. The best you can hope for is a well placed shot that hits the central nervous system in some way whether it be spinal column or brain. Severe Central Nervous System damage is the only way to truly have a one shot stop.

There are books and information available that show the best places to aim for to try to achieve CNS damages.
 

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Lots of good info here, I don't feel I can add anything to the discussion except this - don't worry so much about using the "right" ammo. Any top-shelf JHP from one of the major American manufacturers is going to get the job done - expansion isn't the problem it used to be. Once you start comparing numbers and charts you're in the realm of minutae that isn't nearly as important as the fundamentals; accuracy and reliability are more important than terminal performance. Pick a brand that works flawlessly in your weapon, practice regularly, and don't worry about one particular weight or brand of ammo having a 20 fps advantage over another. If you can put bullets where they need to be when you need them to be there you're good to go!

:mrgreen:
 

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Lots of good info here, I don't feel I can add anything to the discussion except this - don't worry so much about using the "right" ammo. Any top-shelf JHP from one of the major American manufacturers is going to get the job done - expansion isn't the problem it used to be. Once you start comparing numbers and charts you're in the realm of minutae that isn't nearly as important as the fundamentals; accuracy and reliability are more important than terminal performance. Pick a brand that works flawlessly in your weapon, practice regularly, and don't worry about one particular weight or brand of ammo having a 20 fps advantage over another. If you can put bullets where they need to be when you need them to be there you're good to go!

:mrgreen:
amen to that!
 

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Lots of good info here, I don't feel I can add anything to the discussion except this - don't worry so much about using the "right" ammo. Any top-shelf JHP from one of the major American manufacturers is going to get the job done - expansion isn't the problem it used to be. Once you start comparing numbers and charts you're in the realm of minutae that isn't nearly as important as the fundamentals; accuracy and reliability are more important than terminal performance. Pick a brand that works flawlessly in your weapon, practice regularly, and don't worry about one particular weight or brand of ammo having a 20 fps advantage over another. If you can put bullets where they need to be when you need them to be there you're good to go!

:mrgreen:
Nice summary there. Lots of bullets are great, just learn how to use 'em!
 
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