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Do cartridge case dimensions affect recoil?

 
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Old 11-17-2010, 09:36 PM
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Do cartridge case dimensions affect recoil?

I was recently having a good natured discussion on another thread about whether cartridge case dimensions affect recoil. I don't think so but I've been wrong before. So educate me if I'm wrong.

My impression is that recoil is dependent on rifle weight, bullet weight and velocity, and weight of powder charge. There could be other minor factors affecting recoil but cartridge dimensions is not one of them.

The other view expressed, as I understand it, is that if all other things are equal, a short fat case will have more recoil than a long thin case. Reason being that the short fat case has a larger case head. Thus with equal psi the force pushing back on the bolt is greater. Thus greater recoil.

I feel that until the bullet leaves the bore, pressure in the case is pushing equally in all directions, including the base of the bullet, and these forces, fore and aft, cancel out. After the bullet leaves the bore the jet effect of escaping gases greatly affects recoil. But prior to the bullet leaving the bore internal forces don't affect recoil.

What do you guys think?
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Old 11-17-2010, 10:09 PM
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Re: Do cartridge case dimensions affect recoil?

I am with you. I believe cartridge dia. can affect bolt thrust but bolt thrust is not the same a recoil. Recoil is from the bullet going one way and the rifle going the other. Simple as that right? The heavier the bullet and powder charge the more recoil you will get. Pushing a bullet faster will increase recoil. The lighter the rifle the more recoil you will get. I think they were over thinking it a bit.
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Old 11-17-2010, 10:29 PM
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Re: Do cartridge case dimensions affect recoil?

I am with you as far as the heavier the bullet the more recoil, more powder more recoil, etc....... I believe there is a difference in the felt recoil between a 300 wsm and 300 win mag. Both are pretty similar with about the same performance. The short mags recoil is more of a sharp quick punch to the shoulder compared to the 300 win mag which seems that the recoil isnt quite as sharp but a longer drawn out kick. Its hard to explain, but thats the experience I have had comparing the short mags to their longer brothers.
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Old 11-17-2010, 10:36 PM
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Re: Do cartridge case dimensions affect recoil?

A very excellent question for a sophmore physics student. You have a good intuitive feel for the question, but like many average Americans, damn little science to back it up.

Energy is for a moving body is defined as E = 1/2 M V^2. The up arrow for purpose here will mean to the power of. The equation therefore is 1/2 Mass times Velocity squared. Mass is actually Weight/g, where g is the earth gravitation constant in english units of about 32.2 f/sec^2. E1 is generated by firing bullet and powder out the barrel

Ok.

So bullet, powder leave the barrel at great speed. This generates a reaction equal and opposite which can be the recoil.

E2 is the reaction of the gun and is equal to E1. (According to Newton's third law: The mutual forces of action and reaction between two bodies are equal, opposite and collinear.)

So this reaction is equal to e1 where the mass now is weight of gun, scope, sling, etc divided by g.

Now that you have the physics, we can see that only things accelerating (F = ma) have an effect on recoil, not the case size.

By the way, keep your velocity down, these equations go out the window as velocity of bullet approaches speed of light, something that really worries some scientists!
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Old 11-17-2010, 11:12 PM
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Re: Do cartridge case dimensions affect recoil?

Quote:
Originally Posted by Varminator 911 View Post
I was recently having a good natured discussion on another thread about whether cartridge case dimensions affect recoil. I don't think so but I've been wrong before. So educate me if I'm wrong.

My impression is that recoil is dependent on rifle weight, bullet weight and velocity, and weight of powder charge. There could be other minor factors affecting recoil but cartridge dimensions is not one of them.

The other view expressed, as I understand it, is that if all other things are equal, a short fat case will have more recoil than a long thin case. Reason being that the short fat case has a larger case head. Thus with equal psi the force pushing back on the bolt is greater. Thus greater recoil.

I feel that until the bullet leaves the bore, pressure in the case is pushing equally in all directions, including the base of the bullet, and these forces, fore and aft, cancel out. After the bullet leaves the bore the jet effect of escaping gases greatly affects recoil. But prior to the bullet leaving the bore internal forces don't affect recoil.

What do you guys think?
There are two kinds of recoil, Recoil energy (Total force backwards) and Recoil velocity (The speed at which the weapon moves backwards ) This is sometimes called "Felt recoil".

If you look at the formulas for calculating these types of recoil they do not include the case size
or shape. Only the bullet weight,caliber, powder in grains,velocity and the weight of the
weapon.

Heaver bullets= More recoil, more velocity=more recoil, less weight of weapon= more recoil ,ETC.

The only reason to feel a difference between two cartriges of different shapes if all other
things are equal is the burn rate of the powder that is used. A faster burn rate that produces
the same velocity with the same bullet and weight of rifle will reach peak pressure faster
and increase recoil velocity and that might be mistaken for more recoil.

It is as Dmci Stated (Newtons law applies).

So even if it feels like it recoils more, if everything is the same it doesn't. Felt recoil can be
deceiving because even the fit of the stock can change the perceived recoil. Just like if you
hold a shotgun tight against your shoulder and fire it then hold it away from your shoulder and it will recoil more because in reality it weights less because you shoulder is not adding any weight
to the shotgun like it does when held tight.

I hope this helps explain your question.

J E CUSTOM
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Old 11-17-2010, 11:55 PM
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Re: Do cartridge case dimensions affect recoil?

The bullets part of it, the gas is the other, muzzle brakes work for a reason.
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Old 11-18-2010, 02:50 AM
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Re: Do cartridge case dimensions affect recoil?

Quote:
Originally Posted by ovastafford View Post
I believe there is a difference in the felt recoil between a 300 wsm and 300 win mag. Both are pretty similar with about the same performance. The short mags recoil is more of a sharp quick punch to the shoulder compared to the 300 win mag which seems that the recoil isnt quite as sharp but a longer drawn out kick.
Another good question.

Let's put this one in engineering terms. A firearm is really a machine that converts stored chemical potential energy (in the primer and to a greater extent the powder) into kinetic energy of the bullet in flight.

Bottom line is we must look at the efficiency at which our one cylinder internal combustion engine operates. A whole host of variables are at play here. Bore, barrel length, bullet weight and configuration, desired muzzle velocity, etc.

Compare for example the .45 Cal. Colt 1911 to .338 Winchester rifle. Different performance, different parameters, but both can shoot a 230 grain bullet. Comparing the .300 WSM to the .300 Win Mag is a much more subtle comparison but the same principles apply.
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