quote:

Originally posted by jeffeosso:
of course you can feel twist, especially in some notables ... the hyem 600 NE twists like mad, according to some, but the faster twist 600 OK isn't nearly as bad.. according to more...

I can't understand that one unless it has something to do with stock design or something to do with the shooter.
A left-handed shooter would get smacked in the face worse by a right-hand twist barrel.
A right-handed shooter benefits from the stock twisting away from his face with a right-hand twist barrel.

however, faster twist requires more energy consumed to exist the barrel, assuming same length

that energy is brought back to you in recoil...

A semantic correction: Recoil from twist is torque, and it is not "brought back to you in recoil": It goes sideways in your hands.

its math, gents

quote:

Originally posted by ALF:
Twist rate absolutely plays a role in magintude of recoil!

( Source: Gemmerhausen R. Handbook of Weaponry 2nd edition Rheinmetal industries Germany)

It's a fundamental principle of gun design.

Greener did not assume this based on some calculation or theory but observed this by comparing the behaviour of a smoothbore gun to a rifled gun in a ballistic pendulum.

The principle of this observation derives from the physics of recoil which is defined as a gun behaviour to the impulse or time derivative of pressure generated in the gun by the projectile as well as the after effect of the projectile and gas egress from the barrel of the gun ( gas after effect)

Pressure resulting in forces acting on the gun system is directly related to to forces of retardation of the projectile in the barrel.

The main forces are gas force, projectile resistance force and rifling force. The effect of rifling is quite apparent when comparing the Lagrange curves for guns of varying barrel twist rates.

Twist angle is important in calculation of these forces. The higher the angle of twist the greater the force.

In calculating the magnitude of total force acting on the gun system this has to be taken into account and is when designing gun recoil systems.

Whilst in small bore hand held and shoulder arms the contribution my be small and most often dwarfed by other design considerations the principle still holds that twist angle plays a role in the behaviour we define as recoil.

quote:

Originally posted by ALF:
Torque produced by the spin of the projectile is relatively small compared to the torque produced by the unbalance produced by the lack of collinearity between centre of mass of the guns recoiling parts and the linear momentum of the projectile and the jetting gas mass.

It is the "explosion of the propellant" that causes the torque force that we see as muzzle or gun jump and not the spin of the projectile. hence the term " Powder couple" used to describe the unbalanced force.

If you calculate rotational momentum or rotational energy of the projectile is minuscule compared to linear momentum end energy; what is more the bullet does not sit in the barrel and spin like a top, it makes 2 to 3 full revolutions only and its gone.

Though there are the the age old rules of opposite and equal forces and rules of conservation of momentum and energy the gun stays put and the bullet is launched.

SUSPEND REALITY, eh?

In a 5 pound 223 rifle the mass of the bullet is but 0.13 % of the total recoiling mass of the gun,
It is the bullet that becomes engraved and not the barrel, it is the bullet that is spun and not the barrel.

But a small mass at high velocity has significant momentum, enough to contribute sensible torque IF REALITY IS NOT SUSPENDED.

quote:

Originally posted by ALF:
????

Dont know what you are trying to get at with your last statement?

Perhaps less obscure and totally googleable !

Ingalls, yep your very own US born and bred, he stated:

The energy of combustion is expended in the following manner:

(a) In Kinetic Energy of translation of the projectile. (83%)

The rest 17%

(b) In Kinetic Energy of translation
of the recoiling mass (assuming the
recoiling mass free).

(c) In the Kinetic Energy of the charge itself.

(d) In the work on the rifling and in friction.

(e) In the angular energy given to the projectile.

(f) In dissipated heat.

The last three are very small when compared with
(a), (b) and (c).

Further (b) and (c) are small as
compared with (a).



Anyway just thought I would look in and play a bit......

Now I will depart again
have yourself a great Christmas etc etc.

quote:

Originally posted by RIP:

Smoothbore: No torque.
Rifled bore: Torque.
Faster twist rifling: More torque, a lot more with a 577 T.rex shooting 900-grain bullets at plus Mach 2 using only about 160 grains of powder.

quote:

Originally posted by RIP:
Torque does not depend on mass alone.
It is derived from momentum, the product of mass AND velocity.
Yes, the rifle is a lot heavier than the bullet, but the rifle also moves a lot slower than the bullet.
That is one reason, among others, that it does not kill on both ends.

quote:

Originally posted by TX Nimrod:
Next to the REPLY and FIND buttons the IGNORE button is my most-used board function. Amazing how it eliminates the rude behavior of others....like magic.


.

Jim
"Life's hard; it's harder if you're stupid"
John Wayne

quote:

Originally posted by ALF:
RIP:

I see nothing has changed on AR

Anyway back to the problem at hand:

Recoil and twist rate : the why and the how ?

So we are spinning a bullet, not a point mass object but a bullet with mass located in a form and shape and we are spinning it around a fixed axis. ( spinning top)

We are looking now not at simply mass and velocity as a product but rather the effect of the spatial arrangement of multiple mass points in orbit around a fixed axis; we are dealing with the transverse mass moment of inertia of our bullet...... exactly the same parameters at play when that bullet is in flight and when it impacts and penetrates a target.

And to those who still cling to the idea that sectional density is a myth or some cooked up entity here it rears its head once more..... mass arranged in a space with shape and form and thus a presenting surface area in direction of motion..... the forces generated by rotating mass in this arrangement are added to the equation.

As momentum is a vector we see that the vector direction of angular momentum lies in the same axis as the long axis of spin which in effect is the same as the direction of bullet progression. so this momentum direction is the same as point mass momentum, the quantity however is different but is added to the linear momentum of the bullet...... it has to be because a spinning bullet has more energy than a non spinning bullet. So by spinning the bullet we are adding momentum to the equation and that comes back to bite us in the form of added recoil

When designing guns the main forces accounted for in recoil are devided in two major categories.

a) the forces accounted for during the combustion of the powder charge and b.) the forces after projectile egression from the bore of the gun ( this is countered by the use of muzzle brakes)

The forces associated with recoil are:
1. The gas pressure force or combustion force ie the pressures brought about by the effects of combustion and the inertia of the projectile
2. the effect projectile spin
3. the mass of the recoilling parts of the gun
4. the mass effect of the static or non recoilling part of the gun.
5. the effect of the anchor point of the gun, ie shoulder , platform or carraige.

quote:

Originally posted by ALF:
RIP:

I don't think there is much to add other than to say it may not be a huge issue when shooting our shoulder fired guns.... a few foot pound of recoil added or not perhaps of little consequence.

Where is becomes an issue is when we are dealing with large bore guns such as howitzers etc.

Now we are not just dealing not just with the recoil of the gun in the axis of projectile motion but the barrel is elevated and the designer has to contend with gun jump in this position. The positioning of recoil damping devices relative to the axis of the bore becomes a consideration, so does gun mount or carriage stability.

What is interesting for me is when does the recoil occur in terms of a Time line.

If total momentum and energy is equal and opposite then at what point does the recoil motion of the gun start relative to the start of projectile motion in the barrel. is it coincidental or is there a time lapse and how big is this lapse and why?

Is the barrel jump already in in motion before the bullet has left the barrel, or is it still in the barrel ? This then adds another dimension to recoil effect. It you hold the gun tightly vs a loose grip on the gun or resting the gun on a rest or bipod how does this effect barrel motion and the position of egress of the bullet?

quote:

Originally posted by ALF:
RIP:

I understand exactly what you are saying or observing based on these pictures. Intuition certainly would bare this out because one would think that the barrel would react or spin in the opposite direction than the bullet not so.

What we do not know about this particular rifle is where it's centre of mass is located relative to the long axis of direction of fire and secondly what effect the point of anchor has on the gun motion.

We I look at gun carriage balance physics the phenomenon is termed "torque reaction of the projectile"

This directly proportional to the powder reaction on the projectile and then the pitch angle of the rifling. The angle of pitch increases torque for a given pressure. The direction of the reaction of the barrel to this seems to be directly up and back.

This then comes down to physics and physical terms. Torque is defined as the rate of change of angular momentum and the direction of angular momentum is coincidental to the axis of fire of the gun. So the effect of spinning the projectile in the barrel adds to the forces in line with the axis of the bore.

I have always been amazed at how narrow and high above ground level some old cannon carriages were. The Boers for instance used a battery of cannons mounted on field carriages fondly named the Long Tom.

This gun had a very narrow high off the ground carriage and the trunnions were placed high above the ground. These guns did not fall over to one side when fired due to spin.