Recoil Question

[Parajoe]

I have been thinking about this drawing on previous knowledge and I'm not sure of the answer. Does the rifle recoil after that round has left the barrel or does it actually start when the primer ignites the powder charge? This has been irritating me for a bit now. Thanks,

JOe

[quickdtoo]

I think it's pretty basic physics, for every action, there's an equal and opposite reaction, primer ignites powder, burning powder creates gas, bullet starts moving, recoil starts when the bullet starts moving. Bigger and/or faster the bullet, more reaction = more recoil.


Tim

[Parajoe]

Well I understand that!! When shooting pistols and calling shots, where the sights were the shot broke, is where the hit is most likely assuming all other factors are in line. For instance, no flinching. The theory behind this is that the bullet has left the barrel before the gun has begun to fully recoil. The reason I'm asking is because when shooting I'm letting the gun free recoil, and wondering if doing this will let the shot "get away".

JOe

[Sweaty Bullitts]

I believe I've read somewhere that the recoil doesn't actually happen until the bullet has left the barrel because the pressure exerts equally between the bullet and the chambered case.  The pressure is pushing the bullet forward, and the chambered case rearward, cancelling each other out.  Once the bullet has left the barrel, now the pressure can only exert against the chambered case, pushing it back, which starts the recoil motion.

Sounded good to me....

Sweaty

[Sourdough]

From what I have read, recoil starts as soon as the bullet starts moving.  The bullet is moving so fast that it actually exits the barrel before the recoil has time to move the gun.  Felt recoil happens after the bullet leaves the barrel.

[quickdtoo]

As Sourdough confirmed, recoil starts when the bullet starts moving, plain and simple!!

Tim

What is recoil? It originates in the laws of physics: For every action there is an equal and opposite reaction. When the bullet goes forward, the rifle goes backward. It’s that simple. The amount of recoil is determined by a bullet’s weight and velocity, but the gun’s weight must also be factored in. A heavy gun shooting the same bullet and powder charge produces less recoil than would a lighter weight gun.

http://www.galleryofguns.com/shootingtimes/Articles/DisplayArticles.asp?ID=3251

And a more scientific explanation..

Recoil
When you fire a gun, the bullet leaves the barrel at a high velocity, on the order of thousands of feet per second. The laws of physics say that this bullet has a kinetic energy that is determined using the formula:

K=? mv?

where K= kinetic energy, m= mass of the bullet, and v= velocity of the bullet.

According to this formula, energy is directly proportional to bullet size, and the square of velocity. Though especially significant when considering external and terminal ballistics, this relationship is also important when considering recoil. Recoil can be thought of as the reaction caused by the creation of a bullet?s kinetic energy. Newton?s third law of motion states that for every action there is an equal and opposite reaction. Therefore, when a bullet is given a forward energy, there must be an equal energy in the opposite direction; the effect of this reverse energy is what is called recoil.

A number of factors influence recoil, the most obvious of which are the caliber and muzzle velocity of a bullet. These two quantities determine the magnitude of the recoil, but not the qualitative effect of recoil. To determine how the recoil feels, you must take into account variables such as acceleration time, firearm mass, and shooter mass. The acceleration time is proportional to the period over which the shooter must absorb the recoil: the shorter the time, the harder the ?kick? felt by the shooter. Recalling the components of kinetic energy, we find that a heavier firearm results in less recoil absorbed by the shooter; likewise, a heavier shooter will be less likely to be knocked over by the recoil.

Many of the terminal characteristics of bullets are improved by increasing bullet mass and velocity; however, too much recoil leads to shooter discomfort. As a result, a great amount of engineering mitigates the effects of the recoil.

http://illumin.usc.edu/article.php?articleID=61&page=2

[Hammerspur]

As an addition to the 'equal and opposite' origins to recoil, besides the mass/velocity factor there is the 'rocket' effect of the escaping gases from the muzzle after the bullet has exited.

A smaller bore firing a bullet equal in weight to one of larger bore, both rifles using eqivalent or similar powder charges, the small bore will generate greater felt recoil due to the smaller hole the expanding gases will be trying to instantaneously dissipate out of... higher peak pressure would result and the gasses themselves would attain higher venting velocity, generating greater thrust.

Not certain but this might be even more applicable in bottleneck cases versus straight walls due to the narrowing from large case diameter to small neck/bore diameter creating venturi effect induced acceleration of the expanding gas flow.