Magnum not inherently less accurate?

[davidjoe]

I’ve been assuming for years that the greater recoil of magnums increases bullet dispersion. We hear recoil starts immediately, but the gun is really a closed system, - like sitting in the driver’s seat in neutral pushing forward as hard as possible on the steering wheel (futile versus the bumper), - until something moving escapes contact with it, right? If the magnum load bullet is gone before the gun moves backward, does the fact that it moves backward harder and faster indeed have no bearing on group size?

 

[Dub]

for every action there is an equal and opposite reaction

 

[JB10]

300wm 5 shot group at 100yds with 210 bergers. Some can handle recoil and some can not. Does same size groups with 230gr bergers also.

 

[jepp2]

If the magnum load bullet is gone before the gun moves backward,

I'm curious why you believe the gun doesn't move backwards until the bullet is gone?

I'm a believer in Newton's 3'rd law.
______________________________________________

Newton’s Third Law: Action & Reaction​

Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first.​

His third law states that for every action (force) in nature there is an equal and opposite reaction. If object A exerts a force on object B, object B also exerts an equal and opposite force on object A. In other words, forces result from interactions.
_______________________________________________

As the gases expand during the burning of the powder, the gas expands in all directions. However the only locations where that results in movement is against the base of the bullet which moves it down the barrel and the case head, which moves the rifle rearward.

Peak pressure in the cartridge case occurs when the bullet is about 2 inches down the barrel from the cartridge case. After that the pressure continues to drop due to the volume between the case head and the bullet is increasing faster than the burning powder generate additional gas.

​

 

[boltman13]

The rearward travel of the rifle begins as soon as the bullet begins to travel forward, I believe due to Newton's Third Law. Barrel time is very short but still exists. That does not, however, in and of itself make a magnum cartridge less accurate. IF a rifle, powder, primer, bullet and case were brought together with the proper combination for accuracy and the shooter did his part, the result could be outstanding accuracy. The fact that in the uberaccuracy world Magnum rifles are not common is more a function of not wanting to deal with the added cost, less available highest quality components, and greater recoil. In F-Class the Remington Short Action Ultra Mags, and Winchester WSM's are very competitive in skilled hands despite the extra recoil.

 

[Fuj]

Lets add inertia into the mix. Even though there is a short
barrel time, the specific impulse of a magnum is greater.
thus upsetting the rifle sooner and harder in the bullets
barrel travel. So let's say, don't use a 7 lb. 284 Winchester
hunting rifle to shoot F-Class.

 

[davidjoe]

My thought on why the rifle would not move backwards while the bullet is still in the barrel would be, essentially, the bullet and some powder have only moved in the gun from one place to another, until they exit. I don't know if this correct, but to my thinking the rifle prior to bullet exit has fully contained the expansion, it’s like an inflated balloon that is under pressure internally in all directions, but it is not moving anywhere.

 

[Dub]

My thought on why the rifle would not move backwards while the bullet is still in the barrel would be, essentially, the bullet and some powder have only moved in the gun from one place to another, until they exit. I don't know if this correct, but to my thinking the rifle prior to bullet exit has fully contained the expansion, it’s like an inflated balloon that is under pressure, but not moving anywhere.

the rearward motion begins at ignition of the round

 

[BoydAllen]

My thought on why the rifle would not move backwards while the bullet is still in the barrel would be, essentially, the bullet and some powder have only moved in the gun from one place to another, until they exit. I don't know if this correct, but to my thinking the rifle prior to bullet exit has fully contained the expansion, it’s like an inflated balloon that is under pressure, but not moving anywhere.

Your assumption is incorrect. A couple of posters have explained why, also actual experiments confirm.

 

[ebb]

What about newtons 1st law. An object at rest tends to stay at rest. Even if you don't believe that the forward motion of the bullet has to over come the weight of the rifle. Shot the rifle with out holding the forearm and see if it doesn't impact right where it was pointed when the trigger was pulled.

 

[davidjoe]

Your assumption is incorrect. A couple of posters have explained why, also actual experiments confirm.

If we assume that it does start moving rearward on ignition, would the formula for rearward movement, prior to the force of ejection, be based on the “work” performed to move the bullet and some powder forward a certain distance to the front of the barrel, which would be the same distance and weight moved both in a magnum or standard, such that the rearward movement would be the same?

 

[jr600yd]

waiting on the popcorn!

 

[MikeMcCasland]

Torque generated by bigger/heavier bullets is another factor.

 

[davidjoe]

Would a rifle with an infinitely long barrel where nothing escaped from it recoil when shot? Let’s say the air is removed from the barrel in front of the bullet, first.

I don’t know the answer to this, but to me the analogy would be me standing on a flat bed trailer, pushing a lawn tractor from one end to the other. Does my pushing against the flat bed to move the tractor forward have any effect on the tendency of the flat bed to move either forward or backward.

 

[BoydAllen]

Here is a little reading on the subject.

https://saami.org/wp-content/uploads/2018/07/Gun-Recoil-Formulae-2018-07-9-1.pdf

http://past.isma-isaac.be/downloads/isma2014/papers/isma2014_0508.pdf

If you read both very carefully, your understanding of recoil will be greatly improved.

 

[lb-ft]

I’ll touch on the moment the bullet escapes the barrel.

At that moment (and for a duration of many milliseconds thereafter), the component of rocket effect is added to the mix. In the case of the rifle scenario, all the combustion gasses (which are voluminous) force the rifle further rearward. Also, due to most stock designs, upward. At any rate, this particular component of recoil does not exist until the gasses are able to escape out the muzzle.

Oddly enough, the inertial moment of the bullet racing down the barrel is gone now (because the bullet has escaped the barrel). HOWEVER, objects in motion tend to stay in motion. Therefore, though the bullet is now gone and in itself it’s no longer causing recoil, the forces it generated while in the barrel are still affecting the rifle in the form of recoil energy that continues to dissipate energy (into your shoulder).

It’s all really quite fascinating.

 

[davidjoe]

I’ll touch on the moment the bullet escapes the barrel.

At that moment (and for a duration of many milliseconds thereafter), the component of rocket effect is added to the mix. In the case of the rifle scenario, all the combustion gasses (which are voluminous) force the rifle further rearward. Also, due to most stock designs, upward. At any rate, this particular component of recoil does not exist until the gasses are able to escape out the muzzle.

Oddly enough, the inertial moment of the bullet racing down the barrel is gone now (because the bullet has escaped the barrel). HOWEVER, objects in motion tend to stay in motion. Therefore, though the bullet is now gone and in itself it’s no longer causing recoil, the forces it generated while in the barrel are still affecting the rifle in the form of recoil energy that continues to dissipate energy (into your shoulder).

It’s all really quite fascinating.

Boyd’s second article cited at page two, top half, also touches on that instant the muzzle is breached.

A rifle I think differs from say a bow or slingshot which itself is mechanically pushing forward a projectile.

Clearly a drawn bow string, released, pushing an arrow forward must be pulling the bow rearward, in the equal and opposite action and reaction principle.

But a rifle is not itself pushing the bullet forward like s bow or slingshot is. A rifle is merely containing a source of pressure, until that moment all the pressure is directionally released.

I follow the rocket nozzle reference 100%. What I’m not sure about at all is whether a contained explosion in a chamber that slowly increases its volume to reduce pressure, moves the object that constitutes the chamber at all, in just the act of increasing its internal volume, prior to its release.

All of the observable reaction of a Champaign bottle under pressure begins and ends on the cork’s popping, not until then, as it inches forward. Does the cork’s slight travel forward under pressure as you break friction move the bottle slightly rearward, I don’t know.

It is interesting to me because if a magnum’s increased rearward or upward motion really only starts after the bullet is gone, then the shooter and rest must absorb it of course, but it won’t account for any larger group size.

 

[Alex Wheeler]

Yes the rifle recoils when the bullet is still in the barrel, it also torques. Its very obvious when building the larger magnums that theres a weight threshold you have to maintain or you see the accuracy degrade. It has nothing to do with the recoil the shooter experiences.
Edit, the 60k psi in the rifle acts in all directions, the base of the bullet as well as the bolt face, they are driven in opposite directions the instant theres enough pressure to move the bullet.

 

[std7mag]

waiting on the popcorn!

Got my popcorn!
Roll the slow motion cameras!

 

[Fuj]

A little scientific debate is good for the soul.