recoil

[glo]

Hi Cliffe,
Sorry, I should have paid more attention and used numbers germane to this thread. The numbers I came up with were from my reloading manuals. I was trying to match the velocity from two different loads for the .308 and 30-06’. I believe the matching velocity for the cartridges was 2780fps. As I recall the .308 powder was moderate in burning rate and 06’ powder was slow; hence the 8 grain difference.

BTW just to illustrate how the numbers can get confusing,going back to your original question) here is another example; a .30-06 is more efficient than a .308!!!

I got this load from Hodgdon website. The 06’ from Hodgdon test barrel produces more velocity with less powder than the .308. The recoil energy is also less from the 06’. Here are the parameters: 10 pound rifle; 24 inch test barrel,very positive of that but not on the website); Nosler 150 grain BT; [ .308, 48.5gr Win 748, muzzle velocity 2865fps, recoil 14.75ft-lbf; ][.30-06’, 46.7gr IMR3031, muzzle velocity 2887fps, recoil 14.49ft-lbf.]

You see, anything is possible it you try hard enough.

 

[Akbushape]

Glo, I veiw your post as a positive to this discussion. Never
hurts to have different ideas, experiences and views on any
subject. I have gained knowledge from this thread and appreicate
the input from all posters.,thats why I'm here).
It seems to me the muzzle brake has to do it's work as the bullet is passing through it. As it enters the brake on it's trip to the target the escaping gas hitting the ports in the
brake puts a forward thrust on the rifle barrel which helps
some to reduce the recoil. Once the bullet clears the brake
there is an open barrel for the gases to escape and the brake
ceases to be effective as the pressure in the barrel is relieved.
I'm not qualified to argue about the existence of primary and
secondary recoil, but it seems logical that after the bullet
leaves the brake or the crown if there is no brake there would
be some thrust from the escaping gas the same as the thrust from a rocket blast. if this is the case the rocket blast
would have no interaction with the brake as it would happen beyond the brake. Is this right in the simple form? Or am I still confused?

 

[glo]

I don’t think you are confused. Here is the short and to the point answer. No, there is no thrust by jetting. By design any ejecta and or propellant that comes out the end of gun barrel has already been accounted for within the original event of discharge.

Here’s the long answer: What you are struggling with is what you already intuitively know. Just by living, experiencing and observing things like: a rocket, the space shuttle lifting off, blowing up a balloon and letting it go, dropping a garden hose and letting it spray around wildly; you cognitively associate those events with a perceived thrust or secondary recoil from the muzzle ejecta. Besides you are told this is a true phenomenon by advertises and maybe those with engineering an background who have had to justify ejecta as thrust through a second action; now commonly known as “secondary recoil”.

Let me ask you this, have you ever been kicked twice by your rifle? I haven’t.

Let me say this, for air craft and space craft, thrust is a specific designed function for the vehicle. However, any extra gases left behind after a bullet exits the muzzle have no functionality. The expanded gases are designed for the flight of a bullet. The primarily consideration of the propellant within a gun barrel is to propel a projectile. Ejecta is a by product of the original event of a discharging firearm.

The thought of dividing up the event of a discharged firearm and accounting for each different action is quit normal and natural. It’s how we learn and understand thing. It’s just like when someone says, “You get kinetic energy by adding half more velocity to the momentum equation.” No, that’s not how you get kinetic energy. This is also true for this perceived jetting effect. You don’t add up or parse-out all the different actions of a discharged firearm: primer detonation; powder charge detonation; expanding gases; muzzle ejecta; bullet-muzzle velocity and or firearm kick to justify hot gases coming out the end of your barrel.

I mean let’s be honest here. If flames are coming out the end of you rifle barrel it must be doing something. Well yes… it is. The propellant has just propelled the bullet down the barrel and the rifle back into your shoulder. The ejecta is just dissipating into the atmosphere. The ejecta you are seeing may possess energy but its not pushing back on your gun. The propellant did that while it was in the barrel. That is what is counter intuitive. The propellant in the barrel, which you can’t see before the bullet exits the barrel, creates the “thrust”. The common name is “recoil”. What you see and feel as muzzle ballast dose not affect the gun/ shooter system, it affects you as the independent observer which stands in a new and different system.

 

[Akbushape]

Interesting stuff. What is the factors at work when in one
case the '06 produces more recoil than the 308 using the same bullet at the same speed and in the hodgdon test it is the other
way around? Does this have something to do with how tight the bullet fits in the individual barrels? If there is the slightest bit of difference in the force required to propel the
bullet through the barrel up to a given speed then that difference will translate into greater or less recoil. Is this right? If it is then the recoil between the two guns being debated here is essentially the same, with any variance being
accounted for by the difference in fit and smoothness of the
rifle barrels.
Toby and Gunsmith, get your rearends back here and finish this
discussion . We do value your input.

 

[gunsandgunsmithing]

There have been some good points made in this thread as to how a brake works. I agree with some of them and disagree with some. I'll tell you what I think and let the rest form their own opinion. While I was "technically" wrong about the role that"air" plays,I do believe that it has some influence. A brake does get "hit" by the escaping gasses pulling forward on the gun...some. The major forces at work here are from the escaping gasses propelling the gun rearward without a brake, and are largely negated by a brake. They do have a significant amount of energy...enough from a 50BMG about 5ft. away, to bkeak the windshield out of an old Ford truck,don't ask). This is a clamshell style brake with alot of surface area. The energy that is expelled from the brake is still pretty great. If those gasses can break the windshield in a truck, I think that they would be able to push a gun rearward as well. Another stupid thing that I have done..is to shoot a 30-06 without a brake from the hood of a truck with a bug shield. The bullet didn't hit it, but the percussion did...bye-bye bugshield. If the gasses can do this, I think that they can push a gun rearward. Now, I'm not nearly as edumacated as some on here. I'm just a dumb ol' Kentucky boy that can make a gun that shoots,but I ain't no dummy either. Ask a pistol shooter if a comp works on his open gun. Now ask a shotgunner how much difference porting his trap gun made.....Not much in the case of the shotgun. Not enough pressure to be very effective in a shotgun. Now ask me if muzzle brakes are nothing more than a bunch of gunsmith propaganda. They work! You all can figure out how if you want. I'm going to just keep putting them on for people and useing them myself because they can make a 300 mag feel like a 243. Smokeless powder is a propellant. It propels a bullet by creating gasses when burned that expand until the energy in the powder is used up. Many guns still have about 6,000psi of muzzle pressure. That's a pretty fair amount of energy still left when the bullet leaves. That energy does propel a gun rearward. That's all I have left to say. This has been interesting, and thanks to those that made it that way for me. Happy New Year!---Mike Ezell

 

[glo]

I don’t mean to have monopolized this discussion here at this thread, but if there is only one thing I know, it's energy transfer. Gunsandgunsmithing, I grew up in Los Angeles. But I am no Einstein either. If you can make guns shoot, then I have much to learn from you. I posted over in another area concerning cutting stocks. I have cut tens of thousands of board feet of lumber but I still can’t figure out how you guys can take an inch off my skeet gun's butt, add a new pad and it looks like it came from the factory.

You are correct.

The ejecta from rifles, handguns and shotguns is a real force that creates real work. What I have been trying to convey is that the recoil from your firearm is created by the propulsive force before the bullet exits the barrel not the after the bullet exits the barrel. Muzzle blast is very much part of squeezing the trigger. Think of it this way, you are not next to the gun. You are behind the gun. By the time you recover from the recoil, the muzzle blast has blown out your wind shield of your truck and the bullet is several hundred yards down range. Boom… It all happens at once. You can’t see it happen, you just feel it happen.

The muzzle brake works by recovering some of the energy from the muzzle blast and pulls the barrel forward. There is no secondary recoil or extra added energy or rocket engine-jetting. That’s what you think you see if you are watching someone shoot. Again, you are behind the gun. A muzzle brake in another word is an air brake. The same thing used on air craft. Mechanically it is a sail. And when you drop the hammer on a 50cal you really want that gun to sail away; no muzzle brake… No more shoulder!

Porting is mechanically the same as braking except that porting robs the bullet and recoil of its energy in order to work. The bullet is still in the barrel and the pressure is redirected out of the barrel via a hole. If you want to call this action jetting then so be it but technically this is also incorrect.

The mechanism at work is the same propulsive force that is pushing the bullet down the barrel and gun back into your shoulder. Now, that propulsive force is pushing down on the barrel. Felt recoil is reduce by mechanically keeping the firearm ergonomically,limiting muzzle jump) in the correct shooting position. Also some of the actual energy is redirected away from the base of the bullet and you the shooter as to barrel in a designed downward direction. There will be a drop in muzzle velocity. That’s why I say ports rob bullet and recoil energy.

Let’s keep the dialogue going so we can dispel all of these old-wives-tales.

1/02/09 Note: The associated damage to a vehicle due to the near proximity of the muzzle from a discharged firearm is caused by the shock wave create by a bullet’s supersonic velocity. The amount of energy transferred and ability to create such damage is dependant on the diameter, length and velocity of the bullet.

 

[glo]

Question: What are the factors at work when in one case the '06 produces more recoil than the .308 using the same bullet at the same speed and in the Hodgdon test is it the other way around?
Answer: Part 1, 06’ vs .308; all things being equal except the powder charge weight. It is the greater weight of the powder charge within the 06’ case than the .308 case wich cuases the greater recoil. Part 2, Hodgdon reloading recipe; In figuring recoil there are two weights, the powder charge and bullet. There are also two velocities, one for the powder charge and one for the bullet. Therefore there are 4 ways to tweak the numbers to make one cartridge create more recoil than the other. Again all things beeing equal. As you may know there are about one hundred different powders. Each powder will create a different velocity from any one bullet. Also the weight of each different powder charge will be different.
Technical this all comes from Newton’s second law of motion. F=ma

Question: Does this have something to do with how tight the bullet fits in the individual barrels?
Answer: No, not in this case. But yes in general. A tight bullet fit creates more inertia. More inertia requires more energy to overcome. More energy means more recoil and typically more velocity but not necessarily.

Question: If there is the slightest bit of difference in the force required to propel the bullet through the barrel up to a given speed then that difference will translate into greater or less recoil?
Answer: Both greater and lesser recoil. There are a bunch of factors that effect attained muzzle velocity. In the case of lesser recoil some of the reasons can be: bullet coating and barrel coatings reducing friction; powder burning rate being optimized to create the greatest possible muzzle velocity with the least amount of powder; cartridge brass not stretching due to hardness and or chamber fit, neck tension; bullet to barrel fit optimized, correct rifling geometry and on and on and on. As it pertains to greater recoil just reveres some of the preceding factors: Low quality bullet that causes bullet friction; powder burning rate being to slow or to quick to create the greatest possible muzzle velocity with the least amount of powder; cartridge brass stretching due to hardness and or chamber fit, neck tension or crimp; bullet to barrel fit bad due to quality control, incorrect rifling geometry and on and on and on.

Question: Is this right?
Answer: its both greater and lesser recoil.

Question: If the recoil between the two guns being debated here is essentially he same, is it then with any variance being accounted for by the difference in fit and smoothness of the rifle barrels?
Answer: Same as above, quality control. If the barrel to bullet fit is good and the barrel internal surfaces are good, than it will take less force to attain the same velocity from on load to another. Less force translates to less recoil. This last question is exactly what Newton’s second law of motion is stating: Any change of motion of a body is proportional to the force impressed on the that body, and happens along the straight line on which that force is impressed; F=ma

 

[Akbushape]

So this gets back to what I thought at the beginning that the
recoil should be the same out of both rifles. Any variance in
recoil is a product of all the items you listed above. It is possible to have either gun produce more recoil than the other
while sending the same weight bullet out at the same MV.
Since either gun can produce more recoil under the listed paremiters they both esentially produce the same recoil. You can tweak either one either way by messing with barrel tolerances, smoothness, lubrication etc. etc. Is that a fair statement?
Sorry, not deliberately thick headed, just born that way.

 

[glo]

I think you've got it.

No, your not thick headed. The topic of kinetic energy is now a high school level class, but thats only if your mathematically incline and opt to take physics as an elective. If not you are doomed to never understand the language of science and engineering. Thats because science and engineering has its own definitions for the same words we use everyday.

The most glaring example is the word “pound”. Most folks think a “foot pound” is the amount of energy required to move a pound through the distance of a foot. Unfortunately this is a misnomer. The foot and the pound are the derived factors of dF. Where as d is distance and its unit of measure is the foot and F is force and its unit of measure is the pound force. The pound force is not the same thing as the pound mass. You probably know the pound-mass as just “a pound” or the “pound Avoirdupois” which is weight. The pound force is force and is equal to the earths gravitation acceleration of 32.1739feet per second squared.

Most folks have a hard time quantifying energy. That's why when we are trying to quantify the work,scientific definition, energy) something can do we use power to represent that work; horsepower and watts. Power is energy per time. One watt is equal to 1 Joule per second and one horsepower is equal to 550 foot-pound force per second. The Joule and foot-pound force are the same units we as hunters and shooters use to represent recoil and bullet energy.

BTW any of you folks from across the pond who need to understand what I'm conveying in SI, let me know. I'll be more than glad to make the conversions and explain the differences.

Happy New Year!!!