Home Forums Hunting & Shooting Hunting Rifles Do longer barreled rifles (guns) recoil more?

or to ask it another way, when does recoil start?

It would seem to me that it would start (physics) the moment the bullet begins to move. If so, then it would also seem to me that the longer barrel would give the bullet more "barrel time" which would, in turn, make the longer barreled gun have a greater recoil impulse. What do you think or know? (I realize it's largely theoretical since recoil has many variables and is very subjective.)

Here's my unscientific guess,

If you have two identical weight rifles, same cartridge, load, weight, but one with a 20" barrel and the other with a 30" barrel. Here is what I would expect:

20" barrel:
more muzzle pressure = increase in recoil
Less velocity= reduction in recoil

30" barrel:
less muzzle pressure= reduction in recoil
more velocity=increases in recoil

...Darned if I know,

MM <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />

General theory is that recoil certainly starts before the bullet leaves the muzzle. Newton's third law would certainly support this assumption. However, the acceleration of the rifle is far slower than the acceleration of the bullet and gas so any pre-exit movement of the rifle would be minute. I know of no studies to verify or quantify this, and certainly no recoil calculation considers barrel length within the equation.



Kinda like muzzle pressure, you know it's there, it's probably a factor, but you can't quite prove it, or put a number on it.



JimF

http://www.handloads.com/calc/recoil.htm

For S&G, I ran a comparison on this recoil calculator, attempting to approximate a 30-06 load. I figured the following data for both loads:

bullet: 180gr
charge: 60gr
weight of rifle: 8 pounds

Velocity: 2700(20"bbl), 2900(30"bbl)
recoil: 2700, 20.88ft-lbs. 2900, 23.00 ft lbs.

MM

it goes along the lines of JimF. Action/Reaction! But the reaction in a time scale of recoil is much longer than the time the bullet is in the barrel, so the reaction is small considering recoil while the bullet is in the barrel. Some people who shoot handguns do however notice effect, it shows up sometimes significantly in a POI shift between different cartridges in the same firearm.



The recoil is the combined conservation of momentum of the exiting bullet and its propellent gases. The system (bullet, powder, rifle, and shooter) has a zero momentum just prior to the rifle being fired, the systems total kinetic energy is zero (both momentum and energy are conserved ... must be the same before and after firing the rifle). Since there is a certian amount of kinetic energy in the bullet and escaping gases going in one direction, there needs to be kinetic energy (or momentum) going in the opposite direction since the total energy of the system needs to be what it was prior to the rifle firing (zero).



With all things being equal (both rifles having the same mass, same bullet mass, same powder charge, and same bullet velocity) the recoil will be equal.



In reality, longer barrels wiegh more (lowering FELT recoil) but usually produce greater bullet speeds (increasing FELT recoil).



I know I butchered the explaination, but I hope is a trifle clear than mud.

Any of the equations I have seen for figuring out the recoil energy of a rifle take into account the weight of the powder charge, the weight of the rifle, the weight of the projectile and the muzzle velocity of the projectile. Assuming all other things are equal, the barrel length should have a minimal effect. Assuming a muzzle velocity of 3000 fps, and a barrel length of 2 ft., it can be seen that the bullet is in the barrel for about 1/1500th of a second (give or take) That isn't long. If the barrel length was 3 ft, the factor would be 1/1000 second. Still not long. So a couple inches here or there shouldn't affect the recoil, assuming the weight of everything is the same, and the MV is nearly the same.

Weight of rifle and muzzle break has a lot more to do with reducing recoil than anything else.

True. It doesn't add much in terms of actual time but in your example the time is actually increased by 50% in the longer barrel so looking at it that way the increase is considerable. Even going from a 20" to a 24" barrel is significant percentage-wise (20%). Certainly we wouldn't scoff if we got that much of a percentage of increase in velocity. Then again, I suppose the actual barrel time of a bullet in that last 4" would be significantly less than the barrel time of the bullet in the first four when it is still accelerating rapidly.

I know this is an almost meaningless question but it's kind of intersting to think about...

I would think a longer barreled rifle would recoil less because the extra barrel length should add more weight. The more a rifle weighs, the less the recoil is. I recently shot a Savage one of my brother in laws bought in 30-06. It is the hunter series, and the first thing I noticed about the rifle was it was very light in weight. After several rounds, he wanted me to shoot it, and I could see why, it's recoil was considerably worse than my 7mm Rem mag, model 700. I think weight of rifle has more to do with felt recoil, so it stands to reason that a longer barreled rifle should recoil less, unless it is a fluted barrel and weighs less than the original barrel, etc.

Why do you ask? Are you considering building a rifle and contemplating barrel length? There are many variables that effect how you feel recoil that need consideration.

No, the question is largely one of attempting to understand the physics of the "shot." The way I see it as long as the bullet is accelerating it should be creating the opposite force (recoil) but, then again, maybe recoil is only generated during a certain "angle" of the acceleration curve - like when the bullet is just starting out and increasing in speed very rapidly.

I choose whatever barrel length I want over what I think is better for some reason. I like short barrels because, to me, they are handier. But I also have a couple that are 26".

165 grains moving east at 3000 fps will produce recoil -- the equal and opposite reaction -- of the same degree west. The heavier the rifle, the less the shooter will feel, all things being equal, because more of the 'equal and opposite' energy will be used to move the rifle, as opposed to moving the shooter.

Since longer barrels are heavier, less recoil energy to the shooter.

However, I would not say that it is a difference one would be able to feel.

I await the assistance of an engineer...

.......and then, too, wouldn't two guns; identical in mass, same projectile, same powder mass, same velocity, same time in barrel but different (significantly) muzzle pressure have differing theoretical, maybe measureable, recoil? It seems to me that the "rocket effect" is significant given that devices that vent some gases just before the bullet exits do reduce or redirect recoil.

I understand that "felt" recoil is a whole other and more practical consideration. I also realize that these questions are a complete waste of time to some. I sometimes wonder about "things." It does seem to pass time while waiting and it also allows (encourages) the quarry to sneak in an do the "nose thumbing thing" while hunting sometimes. <img src="/ubbthreads/images/graemlins/tongue.gif" alt="" />

The gun begins to move the instant the bullet does - it has to in order to obey physics. The motion of the gun does indeed change before the bullet exits the muzzle....all one has to do to prove this is to look at the sights on a handgun. On a typical revolver sighted in for 25 yards, the front sight is higher above the boreline than is the rear sight. You'd think that because of this the bullet would land low - but instead it lands where the sights point. This is because the barel is situated high above the pivot point ( the grip ) and a small motion of the gun results in a relatively large rotation of the barrel upwards.

A longer barrel will exhibit more recoil than a short barrel ( all else equal ) because the bullet exits the muzzle at a higher velocity with higher momentum and energy. To satisfy physics, the rifle has to have more recoil energy to balance the extra bullet energy. The only way that a longer barrel would have less felt recoil would be if it weighed significantly more. An extra ounce in weight would not balance an extra 200 ft-lbs of energy. From personal experience, a 10" T/C Contender in .44 Mag recoils noticeably less than does a 14" T/C firing the same ammo.

The question is better asked when you ask about "felt" recoil. I collect M/8 and M/81 Remington autoloaders, a heavy rifle with a surprisingly brutal "felt" recoil. It has been explained to me that the pitch of the stock is the reason, being essentially the same design as the Browning Auto-5 shotgun, also by John Browning. I had an Auto-5 which I hated because of the recoil, and the M/8's and M/81's are the same. Firing the same cartridges (.30 Rem.[.30-30 rimless] or .35 Rem.) out of a Savage 99 or Marlin 336 is much more comfortable to me (and others, BTW), so go figure that.

"A longer barrel will exhibit more recoil than a short barrel ( all else equal ) because the bullet exits the muzzle at a higher velocity with higher momentum and energy."

I'm not so sure about that - for example: I know from experience that a snubbie .357mag revolver has more recoil that a 4 or 6 incher does, and in a Mosin-Nagant rifle, an M-44 Carbine has more recoil than an M-91/30 does, soo.... No disrespect intended, but those are things I've experienced 1st hand...


- georgestrings

I think you're talking about felt recoil which is different from actual, measured recoil. One of the factors in felt recoil is muzzle blast which a shorter barrel may have more of. Also, in a handgun especially, the way the gun directs recoil will affect our perception of it. A shorter gun will swing a shorter arc which, again, especially in a handgun, is going to feel sharper.

"Do longer barreled rifles (guns) recoil more?"

That was the question, right??? Ok, if you don't accept the handgun analogy, then how about the M-44 vs M-91/30 analogy??? I know there's a weight difference, but I don't think that's all there is to it...


- georgestrings

A longer barrelled gun has to recoil more, if the weight is the same and the velocity is greater. The recoil starts at the ignition of the powder and the bullet starts moving, and continues until the gases leave the barrrel. If the mass and velocity of the gases and bullet leaving the barrel are significant in the recoil calculations (and they are very significant, of course), then the higher velocity of the gases and bullet have to increase the momentum, so the recoil has to be more.

If the momentum is increased, the recoil is too.


At least I think so.... <img src="/ubbthreads/images/graemlins/tongue.gif" alt="" />