Some books (including scientific books for education) states that the weight of the rifle plus the speed and weight of the bullet are the deciding factors of recoil. With these factors, one can calculate the recoil (speed of rifle going in the opposite direction of the bullet) from a formula wich I don't recall. All of us also know that the stock and balance of the rifle highly affects the felt (or practical) recoil.
Other books say that the pressure of the cartridge also decides the force/speed of recoil.
Ray's statement under the "An excellent Safari Rifle for sale" topic made me wonder how it REALLY is. I will qoute Mr. Atkinson when he compares the 460 Wby to the 458 Lott:

"That big old case when loaded to 2350 actually kicks much much less than the 458 Lott at 2200 FPS....Shot them both the other day was absolutly astounded...but it makes since inasmuch as the 460 was operating at about 35 to 40,000 PSI I suppose."

This seems sensible, so my question is:
If you have two identically shaped rifles in two different calibres firing bullets of equal weight at equal speed (i.e. a downloaded 460 Wby and a 458 Lott), will the recoil be milder with the calibre operating under the lowest pressure? If that is the case, how come?

/Kalle

Kalle....went to the recoil calculator and you need 4 things to calculate recoil.

(1) Bullet weight
(2) Bullet velocity
(3) Weight of powder
(4) Gun Weight

Assuming the rifles are identical in design and weight AND you are shooting the same weight bullet at the same velocity then the only variable is the weight of the powder used to get that level of performance....the answer is you would need to know the weight of the powder used to make the determination.

As an aside.....a guy of Ray's advanced age, after being pounded by broncs and recoil for all those years, probably isn't the best judge for how much a rifle kicks. I would guess if he keeps his teeth in he feels it isn't too bad...right partner

according to that post the 460 weatherby has a muzzle break on it.

did the Lott?

DB Bill, I assume that the more powder the greater the recoil. I would really appreciate the entire formula for calculating the recoil.

JJHACK, very good point. Didn't think of that, but if that is the case it will certainly explain that particular matter.

Thanks!
/Kalle

Kalle....I've seen the actual formula around but what I use is at this web-site.

www.benchrest.com/sst/

when you get to the site the formula access is on the right...just plug in your numbers.
What it doesn't account for are such things as stock design etc which are very important.

Free recoil formula
bullet weight / 7000 x muzzle velocity + powder weight / 7000 x *gas velocity = rifle weight x rifle velocity (solve for rifle velocity)
Kenitic Energy = rifle weight x rifle velocity x rifle velocity / 64.32
*5200 fps seems to be a good working average for the velocity of the powder gas.
Some of the factors that do NOT affect free recoil but DO affect perceived recoil are TIME (a 378 wby and a 45-110 BP carry about the same ft-lb recoil but one is a puncher and one is a pusher) area the force is applied to, stock shape, slosh tubes (mercuty dampers) muzzle brakes, recoiling parts (semi-autos) shooter mass, etc

[This message has been edited by Tailgunner (edited 04-05-2002).]

I guess I'll jump into this can of worms one more time...

The formulas given above look correct, inasmuch as they tell you the momentum transferred to the shooter. None of those additional factors matter-- the momentum transfer is the same regardless of time, mercury, moving parts, stock shape, etc. However, they DO play a huge part in how objectionable that momentum transfer is to the shooter.

Do the math, shoot some guns with comparable numbers but with radically different stocks and whatnot, and you'll see what I mean. A Lott can be comfortable to shoot. A Marlin Guide Gun may not be, even with only 2/3 the momentum transfer.

Pertinax

Thanks for the informative answers!

Pertinax, hence that I wrote "All of us also know that the stock and balance of the rifle highly affects the felt (or practical) recoil." One must offcourse also include such things as brakes and mercury recoil reducers that statement.

/Kalle

Pertinax:
I think you and I are just using different terms, but we are both saying the same thing.
I copied the formula from one of my loading manuals, so I would hope it is correct.

Kalle,

To answer your original question, no-- the one operating at lower pressure will not transfer less momentum to you. However, due to the acceleration curve being different, it may feel somewhat different to shoot. Probably more comfortable, as the gun will be accelerating over a longer time period.

Same issue occurs with light vs. heavy bullets in a given caliber (and the same gun). Both may, according to the math, generate roughly the same momentum numbers. But the lighter bullet may more painful to shoot, due to the rapidity of the momentum transfer.

Pertinax

Interesting post!

I'm fiddling with a small ballistic software of my own. The recoil factors I've used so far are:

Recoil velocity: ((Bullet weight+Powder weight*1,88)/7000)*Muzzle velocity/Rifle weight

Recoil momentum: Recoil velocity (above) * Rifle weight

Recoil energy: 0,5*(Rifle weight/32,17417)*Recoil velocity^2

The velocity of the powder gases seems to be the factor that's applied differently in various formulas I've seen so far.

All comments on the above appreciated!

My recoil formula is pretty simple. I shoot it once and if it uncomfortable or rings my chimes I don't shoot it anymore unless I can do something to soften the blow. Basic rule of thumb works for me.

Another rule...if you can't get off at least 10 controlled shots from a bench...either standing or sitting, you are probably over-gunned because you will never be sure you have it sighted in properly let alone do any load developement.

Wachtel,

You are right about the powder gases being modeled differently in different formulas. There's one thing constant, though-- they are always modeled as exiting faster than muzzle velocity. And LOTS faster, normally. Five thousand fps and 5200 fps seem to be commonly used values. The powder contributes more to the recoil than many people realize.

I haven't simplified the equations to see if yours is right, btw. Supposed to be working...

Pertinax