questions on recoil
 

When does a gun recoil ? Is it when the bullet leaves the barrell ? what causes recoil,
size of bullet or powder burn or what ?
can some explain all this to me.

RE: questions on recoil
 

Well, its the pool ball effect in physics. Two matters pushing equally against each other. The powder burning rate can cause a faster impulse of recoil or slower with the same overall energy. So two guns shooting different powders but getting the same recoil, may feel different with the same ft-lbs of recoil.

What I nor my old professor could figure out is why the recoil formula put powder wieght as so much a dominant factor. Yes, its part of the load leaving but also burning up. Bullet wieght makes perfect sense.

RE: questions on recoil
 

In a way its simple but in a way it isn't. Its easy for me to understan the equal and opposite reaction part and the part bullet weight plays on it. On the other hand FELT recoil is another question. Why do some guns who 's recoil on paper is less,hurt the shoulder more than those with less on paper recoil? I am sure its weight of the gun, shape of the stock, the kind of recoil pad and so fourth. Strange to me is the fact tha I have shot many many rifles, some bigger by far than the 7MM Rem Mag. However the 7MM Mags seam to hit my shoulder harder than the 300 and 338 Mags. Is it recoil speed? It part of it in my head? Whatever it is it hurts.[:@]My 416 Rem mag is the only gun I have owned that hit me much harder than the 7 Mag.

RE: questions on recoil
 

I know the heavier bullets create more recoil, but I seem to feel it more when I use faster burning powders. Maybe slower powders accelerate the bullet over longer time and spread out the recoil over longer time?

RE: questions on recoil
 

I know powder charge, bullet weight, bullet diameter, and gun weight all play a role. If you want to know how much recoil your gun has www.shortmags.org has a recoil calculator, just put in your info and it will tell you. My 300WSM has 30 ft-lbs and my 30-06 has 21ft-lbs.

RE: questions on recoil
 

A lot of people think that pressure affects recoil... not true pressure occurs in all directions, so it has no effect on recoil. One thing to keep in mind is velocity... the faster the projectile, the sharper the recoil. This is why shotgun recoil is so much different from rifle recoil.

bigcountry - I agree that the weight of the propellant (since it is largely in gas form) does not play nearly as large of role in recoil as many calculators indicate

RE: questions on recoil
 

Bingo, you got it. thats the reason sluggun has such a rocket effect. Usually uses much faster powders. Where my 300RUM didn't but more of a slow hard roll. The actual acceleration has to have an effect on felt recoil when graphed over time.

RE: questions on recoil
 

But when does the kick occur ? is it when the bullet leaves the barrell ? is that when the explosion happens ? it seems thats the only way you would have accuracy, when the bullet leaves the barrell.
I mean it couldnt kick when the bullet leave the shell, or could it ?

RE: questions on recoil
 

In principle when the projectile leaves the case is when the kick starts. you have two separate objects separating

RE: questions on recoil
 

Bullet leaving the case would be my guess as well. All guns have a little free bore dont they? I love my 7mag accuracy wise.....but recoil wise it WILL stay in the cabinet. That thing got a sharp punch that I just dont care for. Its a pretty Weatherby or it would go down the road....lol.

RE: questions on recoil
 

How do we get accuracy if the gun starts to move before the bullet has left the barrell ?

RE: questions on recoil
 

Practice, practice and more practice. Seriously, its a short period of time. Thats the reason for good, solide bedding. Or at least one of them.

RE: questions on recoil
 

From a physics standpoint, there are two parts to gun recoil. There is the part where a 180 grain bullet is heading down a 24" barrel at 3000 fps, and driving an 8.7 lb. rifle to the rear ata calculated counter-reaction. Regular physics stuff. And then there is part B: when the bullet breaks its seal at the muzzle and creates a jet engine effect from the gasses exiting the barrel behind the bullet. Part B might be close to half of what your shoulder feels, and is the part of recoil that a muzzle brake serves to mitigate. It is also why the WSM calibers seem to kick less - they use less powder to develop the speed in their short, fat case; and the pressure curve of the expanding gasses is steeper - causing a lower pressure "jet engine effect" when the bullet leaves the muzzle.

RE: questions on recoil
 

Everything i can find about recoil refers to it as a function of momentum. That would imply that recoil is developed as momentum is developed. So IMO recoil must start to build at the same time the bullet starts to move. If a 100gr bullet goes from 0 to 3000 fps in the time it travels down the barrel then recoil would be developed over the same time. I don't think recoil could happen after the bullet leaves the barrel because the bullet dosen't accelerate after it leaves the barrel. I think the inertia of the gun at rest resists the recoil for the .001 or so seconds that the bullet travels down the barrel.

RE: questions on recoil
 

so if I were to use one of those fancy gun rests for sighting in rifles, the one where it straps the gun down like a vice, would it then shoot different if I now hold it on sandbags, or just rest it from a blind or off a bipod.

RE: questions on recoil
 

My browning shoots different from a vise than from a sandbag. Probably be more noticeable in lighter weight guns.

RE: questions on recoil
 

Because even gasses have mass. When you apply a force to accellerate any mass, there in an equal force applied in the opposite direction. Think jet engine.

As for when recoil begins, it begins the instant the mass begins to move. The effect of the gaseous mass accellerating down the bore is also felt immediately because the gas accellerates with the bullet.Also remember that while thegasas a whole may not be moving very fast while the bullet still contains it in the bore, the individual gas molecules are in a veryexcited state becauseof the high temperature and are moving veryquickly.Pressurequite literally is theaverage kinetic energy transfered bythe impact of moving molecules with the surface of an objector containerthey interact with.

Mike

RE: questions on recoil
 

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RE: questions on recoil
 

For what it is worth, there are some interesting photos at www.african-hunter.com/recoil_vs_accuracy.htm. (You can get there through their archives if I botched the address.)

Stock build, the width of the stock and recoil pad and of course rifle weight have a whole lot to do with recoil for me. My son's 308 Tikka kicks more than the 338 Win Mag I had. I believe there is recoil as soon as the bullet leaves the casing, and the barrel reacts as the bullet goes down the bore. But the rock & roll really starts, as far as I know, once the bullet leaves the barrel and gasses escape freely. Otherwise, we would not hit much. But I am open to other thoughts. What the heck. It is an important topic.