In another thread I was told that my approach to calculating free recoil energy and free recoil velocity was wrong. This may well be true! The validation argument used against my method is that it does not match the numerous website recoil calculators.

This is the approach I was using:

Equations are:

v2 =[(bullet + powder)*muzzle velocity]/rifle mass

E = 0.5 * rifle mass * v2^2

v2 is the recoil velocity
E is the recoil energy

All masses are in slugs. To convert from grains to slugs: X # of grains / 225,400. Which is nothing more than 7000 gr/lb*32.2.

Having said all that, what is the correct way to calculate free recoil energy and free recoil velocity? Conversely, does anyone know what equations the website recoil calculators utilize?

Thanks,
Axel

[ 01-29-2003, 21:28: Message edited by: Axel ]

Seems right to me: conservation of momentum plus assumption of constant recoil velocity...

Just a question:

In your calculation, are you converting (bullet + powder) into slugs as well?

Antonio

(((bullet weight/7000) x velocity) + ((powder weight/7000)5200)))/rifle weight = recoil velocity in ft/s

((recoil velocity)^2 x rifle weight)/gravitational constant 64.32 = energy in ft/lbs

[ 01-30-2003, 04:40: Message edited by: Roger Rothschild ]

Roger,
Thank you. I assume that the 5200 is the gas velocity, which is evidently assumed to be greater than the bullet's velocity.

Axel

Axel,

I'm thinking that 5200 is the assumed velocity of the combustion gas (in fps).

Bill

"Having said all that, what is the correct way to calculate free recoil energy and free recoil velocity? Conversely, does anyone know what equations the website recoil calculators utilize?

Thanks,
Axel"

We have always found that discrepancies exist between what is calculated and what actually happens in practise. We always back up our theory with actual test shooting on the range and in field conditions. To determine and compare free recoil energy and velocity we have devised a simple test for which only a stopwatch, two helpers and a first aid attendant is required.

1. Hold the rifle to be tested straight ahead with both arms extended.
2. Place the tip of the nose exactly between the recoil pad screws. This makes you crosseyed but must be done precisely for repeatability of the test.
3. Pull the trigger by squeezing between thumb and forefinger so as to not add to the rearward forces. This will obfuscate the results.
4. Attendant one catches the rifle.
5. Attendant two starts the stopwatch.
6. First aid attendant catches you and lays you down on your side to aid breathing.
7. Free recoil is in direct proportion to the length of the nosebleed as measured with the stopwatch.

Gerard,
You method sounds painful if you are the technician releasing the trigger sear!

Personally, I think that none of the calculated methods are accurate, nor correct. Anyway, let the ignorant ones worry about that. It is also my opinion that the vast majority of individuals that have a hang-up, read interested in, free recoil energy and velocity are in fact suffering from insecurity. These people seem to like to brag about how hard their gun kicks, "SEE I AM A REAL MAN!" Give me a break.

For the record, the worse kicking rifle I ever shot was a 7 pound Savage 110 with plastic stock chambered in 7mm Rem magnum. It was far worse than any big bore I have ever shot.

Axel

[ 01-31-2003, 21:22: Message edited by: Axel ]