Acceleration forces

[NS2]

Here is a weird question, but I thought some one here might know.

How does a rifle manufacturer calculate or simulate the acceleration forces on a barrel?  Can they do it without disturbing the harmonics of the barrel?

Thank you!

[tombogan03884]

Darned if I know, But with some of the CAD sim's that are available they can probably simulate it with out ever touching real metal, and be right.  

[Timothy]

Ask Issac, it's his pesky 3rd law...

Example 1: When a rifle fires a bullet, the force the rifle exerts on the bullet is exactly the same (but in the opposite direction) as the force the bullet exerts on the rifle… so the rifle “kicks back”. The bullet has a mass of 15 g and the rifle is 6.0 kg. The bullet leaves the 75 cm long rifle barrel moving at 70 m/s.

a) Determine the acceleration of the bullet.

Calculate this using a kinematics formula like vf2 = vi2 + 2ad and you should get 3.3e3 m/s2.

b) Determine the force on the bullet.

F = ma will let you calculate the answer 49 N.

c) Determine the acceleration of the rifle.

Again, use F = ma, but make sure that you use the correct mass. You should get 8.2 m/s2.

d) Explain why the bullet accelerates more than the rifle if the forces are the same.

Although have the same amount of force acting on them, they each have a different mass (and therefore a different inertia).

[tt11758]

Ask Issac, it's his pesky 3rd law...

Example 1: When a rifle fires a bullet, the force the rifle exerts on the bullet is exactly the same (but in the opposite direction) as the force the bullet exerts on the rifle… so the rifle “kicks back”. The bullet has a mass of 15 g and the rifle is 6.0 kg. The bullet leaves the 75 cm long rifle barrel moving at 70 m/s.

a) Determine the acceleration of the bullet.

Calculate this using a kinematics formula like vf2 = vi2 + 2ad and you should get 3.3e3 m/s2.

b) Determine the force on the bullet.

F = ma will let you calculate the answer 49 N.

c) Determine the acceleration of the rifle.

Again, use F = ma, but make sure that you use the correct mass. You should get 8.2 m/s2.

d) Explain why the bullet accelerates more than the rifle if the forces are the same.

Although have the same amount of force acting on them, they each have a different mass (and therefore a different inertia).

[Timothy]

My point, exactly....it "wobbles" the mind.....bends the brain..

[Sponsor]

[tt11758]

My point, exactly....it "wobbles" the mind.....bends the brain..

Actually, I understood this part............

Ask Issac, it's his pesky 3rd law...

After that it was like reading stereo instructions.

[twyacht]

Chronograph?

[NS2]

Ask Issac, it's his pesky 3rd law...

Example 1: When a rifle fires a bullet, the force the rifle exerts on the bullet is exactly the same (but in the opposite direction) as the force the bullet exerts on the rifle… so the rifle “kicks back”. The bullet has a mass of 15 g and the rifle is 6.0 kg. The bullet leaves the 75 cm long rifle barrel moving at 70 m/s.

a) Determine the acceleration of the bullet.

Calculate this using a kinematics formula like vf2 = vi2 + 2ad and you should get 3.3e3 m/s2.

b) Determine the force on the bullet.

F = ma will let you calculate the answer 49 N.

c) Determine the acceleration of the rifle.

Again, use F = ma, but make sure that you use the correct mass. You should get 8.2 m/s2.

d) Explain why the bullet accelerates more than the rifle if the forces are the same.

Although have the same amount of force acting on them, they each have a different mass (and therefore a different inertia).

THANK YOU!

I got it after a few minutes of un-cramping my brain.

[tombogan03884]

English instead of metric would be easier to understand as well  

[m25operator]

You also need to factor in the resistance to the projectile, minimum bore diameter versus bullet diameter. A water hose that stays full diameter has little force to the rear, put a nozzle on it to reduce the diameter, and now you have a water wiggle or significant back pressure = recoil and you can feel the hose expand as the water hits the resistance just as barrels do. If you shoot a .30 caliber projectile, in a .38" bore, there will very little pressure or recoil regardless of the charge.

I'm not sure why you would want to map the acceleration unless you were trying something different like a gain twist barrel, to show the improvement, in which the initial acceleration will be faster than when the twist rate starts getting faster. Now theorizing pressure is a different matter, and most gun makers and a lot of ammo makers, use test barrels that are extremely thick, with strain gauges attached at different points on the barrel, this gives real time pressure measurements, and a couple hundred years of engineers notes of pressure capabilities for different alloys, heat treatments in barrels, give a good start. The test barrels give the actual pressure readings of a cartridge, the cartridge is what has been changing the most, with all the new short or super short magnums. Some of the new ultra light barrels need additional testing, due to diminished thickness compared to the norm. I know some of you have seen the tests on the M4's, where they dump mag after mag until the barrel sags and then bursts, not very scientific, but it shows where and how the barrel failed under real firing, I would hate to be the marine who is using his rifle that fast, he would definitely be in the Hurt locker.

Too long as usual, have a good evening.