Velocity Vs. Energy

[Montana Pete]

I tried to correct some folks on another forum for dismissing "a couple of hundred fps of velocity" as "insignificant."

I've seen even professional gun writers make this mistake. Comparing two cartridges, they dismiss the difference of a couple of hundred fps as "insignificant." This is sometimes done to argue that a 308 is virtually the same as a 30-06, or that the 300 Win Mag offers little or no improvement over the 30-06.

Bullet energy is an exponential function based on the square of the velocity. A couple of hundred fps increase in velocity can mean a jumbo increase in energy. Often a 10 pct increase in velocity will equate to a 20 pct increase in energy. Energy is important because it can express itself in damage done downrange, subject to bullet design considerations, and energy is also related to flat trajectory.

On the other forum, most respondents just said the differences between cartridges were still insignificant because the deer you shoot will still drop if you hit it regardless of bullet energy. This seems an apples vs. oranges type of response, dismissing the physics, and suggests that people just want to believe whatever they want to believe. By that logic, a 30-30 is indistinguishable from a 300 Win Mag because if you hit the deer in the heart with either one, the deer will fall down.

I DO think it is a mistake to just brush off the formula for bullet energy and argue that a "couple hundred fps" are "virtually insignificant."

I am not surprised this argument is used by some of the professonal gun writers. I don't have much respect for many of the professional gun writers anyway -- they can and will argue any side of any issue, and are oftentimes little better than shills for the manufacturers. In fairness, not all of them.

 

[chino69]

Velocity vs. Energy

Pete,
Many people either don't know or are unaware of the difference velocity makes. The formula for kinetic energy; K.E. = 1/2 mass x velocity squared will yield surprising results. I don't have my convenient conversion chart handy but anytime one is dealing with an exponent (velocity squared), the result changes considerably.

Lou Baccino

 

[Louis Boyd]

Is 200 fps significant?

The formula for kinetic energy; K.E. = 1/2 mass x velocity squared will yield surprising results.
Lou Baccino

What's the surprise? For a black powder rifle shooting subsonic at 1000 fps adding 200 fps is a 20% increase in velociy and a 44 % increase in energy. That mght suprise someone. The 20% faster bullet will have a flatter trajectory, but it will go transsonic and likely be less accurate at a few hundred yards. SIgnificant? Maybe if it changes whether you hit or miss your target.

How much does 200 FPS mean to a high velocity rifle? Going from 3900fps to 4100 fps shooting 25 grain hollowpoints form a 17 Remington is a 5.12% gain in muzzle velocity and 10.5% more muzzle energy, but that velocity and energy are lost in the first 30 yards out of the muzzle from atmospheric drag. Then the the bullet is back to 3900 fps and continuse as if shot at 3900 fps. So is 30 yards extra raange "significant". Maybe if it changes whether you hit or miss your target.

In both cases you gain the extra 200 fps by burning more than 44% or 10.5% more powder. There's no free lunch.

I don't see why you're worried about anyone who says "it's only a couple of hundred fps lower velocity. It's easy to determine what muzzle velocity is requried to deliver a given amount of energy with a given bullet at a given distance. Some aspects of accuracy such as wind deflection and drop from velocity dispersion are helped by higher velocity. THe terminal energy of a bullet may determine whether a shot was successful. If a bullet does or doesn't make a clean kill, or if it does or doesn't punch though armor it can matter, but in most cases where a shot is succesful the delivered energy is less important than how well it's placed.

Higher velocity and energy are accompanied by more recoil, more barrel flexure, more barrel wear, and more bullet deformation. Most long range match records are held by relatively small cartidges. Most matches are won by intermediate cartriddges. The only place the hightest energy cartridge holds world records is at FCSA matches, where that's the 50 BMG is the only carttridge allowed in the competition.

Tte bottom line is to use the cartridge which will do a given job best. Energy means nothing if you don't hit the target.