Anybody have a formula or some way of calculating free recoil? I think QuickLoad does it, but I don't have a copy of that software. I'm looking to do a comparison of a few different cartridge bullet combos. If someone does have just the equation, I'm not adverse to using a calculator (HP 32SII)

TIA,

Monte

MV=MV. mass velocity out the front = mass velocity out the back.

(Bullet weight(gr)/7000** x Bullet Velocity + Powder weight(gr)/7000** x 5200*) / Rifle weight = Recoil velocity.
Free recoil energy = RW x RV x RV /64.32 (gravity constant).

* different sources cite different gas velocities, some use 1.5 times the bullet velocity as this figgure.
** converts weight in grains to weight in pounds.

Calculating recoil is a momentum balance.

Wg*Vg=Wb*Vb=Wp*Vp

Wg is weight of gun in pounds
Vg is the velocity of the gun, which you will solve for in feet per second
Wb is weight of the bullet converted from grains to pounds
Vb is velocity of the bullet in feet per second
Wp is weight of the powder converted from grains to pounds
Vp is velocity of the powder. An old NRA Rifleman article states that using 4000 fps is a good approximation for most cartridges.

Now that you have the velocity of the gun calculate the kinetic energy of the gun hitting your shoulder.

KEg=0.5*Wg*Vg*Vg

KEg is kinetic energy of the gun

And convert KE of the gun using the gravitational acceleration constant, g=32 feet per second^2 to get units of foot pounds.

KEg/g=recoil in foot pounds

According to an old Col. Whelen book anything over 14 ft lbs will make an average person�s shoulder sore after an afternoon of shooting. If you have Excel you can calculate and compare many different loads and cartridges easily. The general rule is the lighter the bullet and powder load the less recoil.

General numbers off the top of my head:
223 is about 4 ft-lbs
243 is about 7 ft-lbs
308 is about 14 ft-lbs
30-06 is about 17 ft-lbs
300 Win Mag is about 25 ft-lbs

Ben

here's a link to a web calculator



http://wildcatshooting.com/forum/viewtopic.php?t=143



- the text does not say so, but it is there, and, if you go backward to the ballistics page of the site, you'll find the link for the JBM recoil calculator at "sticky-ballistics calculator".

Sent you an E-mail that might help in what you was looking for.

Thanks, guys.

I had found a website afterwards that explained the formulae, and most of the conversions/shortcuts involved here and crunched the numbers by hand. Later someone sent me an Excel spreadsheet that I'm sure works fine, other than I don't have Excel (on a Mac, w/o M$ Office) handy. Couple website links, all of which matched up w/i one decimal place (I calculated to 3, just for giggles) w/ that I did by hand. Musta done something right.

Thanks again,

Monte

The recoil you feel is an Impulse not Energy. Impulse = Momentum. Free recoil is meaningless as
your shoulder mass determines the recoil velocity. If the butt plate dosent move there is no energy
transfer. If you are trying to quantify "Kick" stick with Momentum. Every thing that goes forward has a reaction
back. (Newton).
Good Luck!

Go to the Beartooth Bullets forum online and they have calculators for all kinds of stuff... Recoil, bullet energy, TKO, etc. Just plug in the numbers for your cartridge and in an instant you've got the answers.

Like most physics problems there is a good shortcut formula that works well on a hand calculator:

1. Bullet weight (grs) times velocity (fps)

2. Powder weight times 4700 fps

3. #1 plus #2 divided bt 7000

4. Number 3 squared (or times itself)

5. Number 4 divided by 640


This gives recoil for a 10 lb rifle. Divide by your rifle weight divided by 10.

Go to stevespages.com. There's a good recoil calculator in there! Beats having to fumble around for the rather arcane and complicated formula for computation of free recoil, which can be found in Hatcher's Notebook, as well as other places!

In step five you could divide the figures you get in

step four, by the rifle wt times 64.

Like 10 lbs x 64= 640 ---20lbs x 64= 1280 --- 15 lbs x

64= 960..Overall this is a fast simple formula that I

use. Ed.

Why do you say the energy transfer is the same, or the duration for that matter. Momentum can consist of a
lighter blow over a period of time (recoil pad). The man who has a weight nearest the weight of the rifle would absorb more
energy (better impedance match). This is the mistake in using recoil energy instead of momentum.
Unless you measure the velocity of the shooters shoulder (and it's temperature rise) you can't quantify
recoil. I'm sure what you feel is an impulse into your shoulder not a temperature rise.
A similar problem occurs with "Knock down power". Bullet penetration depends on Momentum
(mass x velocity). Wound cavity size depends on Energy (mass x velocity squared).
Other errors in the gun rags concern shooting uphill, and bullet drift in the wind. (mucho B.S. on these subjects)
Take Care!

Not to argue (to much) with you imagineers, but the term "free recoil" implies just that, that the rifle is free to move as far and fast as it wants to. Us technician types would picture it as swinging free at the end of a pendulem rod or string.
What your discribing would better be called "felt recoil", which is totaly different.

I'm new to shooting but don't you hold the butt against your shoulder, and feel the recoil?.
Please correct me if I'm wrong.
Good luck!

Free recoil is the (for lack of a better term) "magnatude of the energy pulse" caused by the recoil. It can be quantified, as the formulias above show, and as the name (and formulia) implies it does NOT involve the shooter.
Felt recoil is affected by the shooter and the stock design, area and angle that the energy is applied to, hold firmness, technique, position (prone, kneeling, sitting, standing), and can NOT be quantified.
A given bullet, launched at a given velocity, by a given amount of powder, in a gun of a given weight, will yeild the same energy pulse regardless of stock design. How that stock is designed will make a world of differance EX: M-94 Win in 30-30 or a H&R Topper in 410 cause me much more pain than my Mauser 30-06 (The T/C Encore 209x50 muzzle loader hurts more than my CZ 416Rigby), even though the free recoil numbers are higher for the -06 and Rigby due to stock design and fit.
Pliable recoil pads spread the pulse out over TIME, they don't reduce the total force.
Come on up sometime and we'll burn some powder together, doing some comparitive field testing.

To bad there isn't a thumps up Icon on this forum.You and Clark did a good job on felt recoil.The simple picture I tried to draw along with the brief expo were not anywhere as effective as the explanations you two gave us. roger