Handgun bullet trajectory - any general guidelines?

[Brian Pfleuger]

One might notice in those high-speed photos that gases exit the muzzle before the projectile.

Just sayin'.....

A properly sized projectile should allow virtually no gas bypass. I suspect that the vast majority of the gases exiting the muzzle before the bullet are simply the air in the barrel being "chased" out by the bullet.

 

[WESHOOT2]

suspect vs knowledge

High-speed photography allows us to literally observe gases exiting prior to the projectile.
"Should" and "suspect" are assumptions, and false. As the case expands into the chamber gases pass the projectile. The vast majority of exiting gases are a product of the powder's combustion.

If I only had the ability to post the evidence; I apologize for my inability.

 

[Brian Pfleuger]

I've seem high-speed video and pictures that show the gases exiting before the bullet. What I haven't seen is the evidence to determine the source. If you have, so be it. It seems to me that there would be too many variables to make a concrete statement that covers all cases.

If the bullet is properly sized, there should be virtually no bypass once it is engraved in the rifling.

If the chamber is "normal", or at least typical, and the bullets are of typical length, they should be engaging the rifling before they exit the case neck, thereby preventing gas bypass, or at least much of it.

Lead bullet shooters very often speak of preventing gas bypass in order to prevent "leading".

It sure seems to me like the amount of gas bypass is minimal under normal circumstances, certainly minimal enough that it's effect on recoil must be nearly nonexistent.

 

[PawPaw]

In the case of the common revolver cartidges, .38/.357 or .44Spec/.44magnum, there is a lot of gas that gets out while the bullet is in the barrel.

I'm no physicist, but I've been shooting revolvers for a long time, and I know that when I load a heavy-bullet special at 800 fps, then load a light-bullet magnum at 1300 fps, the faster bullet will hit lower on the target than the slower one. I've seen it happen many times in the past 30 years.

 

[9-ball]

Little physics intermezzo

Okay, this is my first post on this forum, but since I'm a physics student, I tought I could sort this out.

Both Mark38 and Peetzakilla have some true points. You're just looking at it starting from other laws. According to the third law of dynamics which Peetzakilla used in his explenation, the momentum will stay the same in the whole system. This however is caused by the actions of the gas Mark38 explained. The only point he got wrong is that the bullet isn't part of the gun, so when the gas pushes in all directions, it pushes against the bottom of the casing and the bullet. Since the bullet has friction, a part of the pressure against the casing is compensated for by the friction of the bullet.

All of the force used to accelerate the bullet will be felt as recoil too. As the gun weighs roughly a hundredfold of the bullet, the weapon will go only one hundreth of the speed of the bullet in recoil. So while the bullet is acceleration from 0 m/s to it's v0, the "recoilspeed" of the gun will be in direct proportion to the speed of the bullet at that particular moment.

And now we're getting to the point. If we look at the generated recoil energy, we see that the part caused while the bullet is in the barrel is only 1/3th of the total recoil energy. The other parts caused by burning gasses when the bullet has exited.

So to sum it up, if someone would really want it, I want to calculate the rotational speed of a recoiling weapon. However, considering the facts I mentioned above, I'm pretty sure it would be fairly pointless, and it would most likely be in the range of some millimeters without any noticable effect in practical applications.

9-ball

 

[Brian Pfleuger]

9-ball,

Your percentages are pretty off there...

"Rocket effect" does not account for 2/3s of recoil, at least not as a general average.

The mass of the powder charge can have an appreciable effect, because a large percentage of it is being accelerated with the bullet and adds to recoil. However, certainly in the case of handguns, the powder charge is fractions of the weight of the projectile. Maybe 8grs of powder compared to a 125, even 180gr, bullet. With rifles, the effect can be greater, as I have loads where the powder actually outweighs the bullet.

On the "rocket effect", this is greatly effected by barrel length because the main factor is muzzle pressure. All else being equal, a shorter barrel produces more rocket effect because the muzzle pressure is higher.

 

[9-ball]

Excuse me peetzakilla,

you are right, my previous results were not calculated with all the exact weights, and since I estimated the recoil with a 1 kg gun but used the recoil measurements of a glock, I was a bit off.

okay, so this time I used all the exact figures:

average % of recoil energy attributed to other effects then accelerating bullet:

58.1
calculated with the measurements of 43 different 9mm loads shot from a Glock.

 

[Mello2u]

http://www.youtube.com/watch?v=otpFNL3yem4&feature=player_detailpage
The above link shows a bullet exiting the muzzle filmed at 1,000,000 frames per second. You will notice that there is gas exiting the muzzle before the bullet. Don't know what cartridge is depicted.

This video takes the time that the bullet travels through the barrel which should be around 7/10,000 of a second and stretches it to about 5 seconds. If you watch carefully you can see a slight (very slight) bit of muzzle rise. Don't know how the handgun was secured for this video.

 

[B.L.E.]

I have a question. I'm sure most everyone here has seen films of super high frame per second cameras slowed way down so you can watch the bullet exit the barrel. I watched one of a M1911, must have viewed it 100 times, trying to educate myself on exactly what happens durring firring. Far as I can tell, the bullet exits, and is at least 10 inches or more from the muzzle before any detectable movement or recoil is seen. So how is it that the heavier bullet shoots higher when there is zero movement of the barrel until after the bullet is well on it's way to the target?

http://www.youtube.com/watch?v=otpFNL3yem4&feature=player_detailpage

Take a look at the above link originally posted by Mello2u. Look at the front sight of the gun while the bullet is still in the barrel, it is moving back.
The barrel and slide are locked together for the first few millimeters of recoil and so the barrel and slide recoil together while the bullet is in the barrel. After the bullet clears the barrel, the rear of the barrel pivots downward to unlock itself from the slide and the slide then keeps going on momentum to finish the cycle.