Recoil Question for an expert

J

JWD

Guest
I see that std vel lr ammo exits the barrel in .003sec , if so then how far would a 10.5lb rifle recoil during this time? Sorry to ask what to some may be an easy/obvious/pointless question but the battery in my senior brain has gone very flat at the moment. Thanks in anticipation Jim
 
I can not answer your question, but you do need to state the rest of the variables.
Variables: is this question disregarding all types of friction? If not then all the drag functions have to be added in to arrive at some sort of answer. which would be difficult to arrive at. Or just set it up in your rests rig a ruler next to it fire around and note the difference. Not trying to be snide here.
 
Given that you have the mass and accelleration of the projectile, the recoil should be directly related to that value (something about equal and opposite reaction???).
 
Herzo, I don't think that would take into account the Drag/Friction of the rifle to any Rest/Rests used or any Slopeing/Angle of the rifle ,all would effect the distance moved from recoil force. Wouldn't it :eek:?
 
Neglecting friction
mV=Mv
40 grain * 1050fps = 10.5*(7000) * v
v= (40*1050)/(10.5 * 7000)
Since there are 7000 grains in a pound
v=0.571428571 fps=6.857142857 Inches per second

Time is going to be the time it took the bullet to get up to speed and then exit the barrel. It exited at 1050 fps (in this example) - now it didn't start at that speed, and did not accelerate uniformly - it accelerated much faster early and then tapered back to only gaining a few feet per second per inch toward the end of the barrel.
If it accelerated evenly the average speed would be 1/2 of 1050, but since it accelerated much faster so early, we can approximate that the average speed will be closer to 850fps Which puts the time in barrel at 24"/(850*12 inches per foot)=0.002352941 seconds
The rifle will reach it's final 6.857 inches per second speed at the same rate as the bullet got to it's final speed so 6.857 (850/1050)=5.55 inches per second average velocity
And the distance traveled going 5.55 inches per second in 0.00235 seconds is 5.55*0.00235 = 0.013061224
Or just a bit less than fifteen thousandths of an inch. Less when you consider friction.

I did make the assumption of a 24" barrel just to make the math easier.
 
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Vibe Sir, your calculations are spot on sir ,They match mine as well On QUICKLOAD .It shows a rimfire rifle at 10.5 lbs with a the bullet velocity at 1080 will move .015 before the bullets exit. Tim in TX
 
Food for Thought.
Shoot a 3 shoot group free recoil.
Put a cement block 1/10 inch behind the butt and shoot 3 more shots at the same group.
Since the bullet has hit the target before the butt hit the cement block there should be no change????
I bet there was - if so why??
 
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Doug said:
Food for Thought.
Shoot a 3 shoot group free recoil.
Put a cement block 1/10 inch behind the butt and shoot 3 more shots at the same group.
Since the bullet has hit the target before the butt hit the cement block there should be no change????
I bet there was - if so why??
Click to expand...
Interference with bench technique.
 
*** Interference with bench technique. ***
Sorry Vibe I do not understand ???

My example has nothing to do with "Bench Techinique"
It is only pointing out that there might be something missing in your math or understanding of all the forces that are involved???
 
Doug said:
*** Interference with bench technique. ***
Sorry Vibe I do not understand ???

My example has nothing to do with "Bench Techinique"
It is only pointing out that there might be something missing in your math or understanding of all the forces that are involved???
Click to expand...
It really has everything to do with bench technique as the rifle itself will not contact the block until the bullet is around 20 feet out of the barrel. Even if that were only 5 foot out of the barrel - it's still out of the barrel and not under the influence of the rifle any longer. So any influence the block might have would only be due to it's interacting with the way you handle the rifle.
But go ahead and do the test and get back with us on what you find.

But also feel free to double check my math and physics, if you happen to find any serious discrepancy there are several here who would like to know about it, me included.
But if it's just because you don't happen to believe the numbers.........Oh well....Be glad we weren't discussing horsepower generated by the rifle upon the bullet. I'm fairly certain you wouldn't believe those numbers. ;)
 
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Way back in the 1920s, Gen Hatcher did a similar exercise with the Cal .30 rifle. He calculated that the rifle moved .06183" prior to the bullet leaving the muzzle. Considering the greater bullet and powder weight, and volume of gas, vs a 22LR, I'd say that the .015" cited above is probably as close as you'll get. Hatcher's tests were done with the rifle suspended on two wires, thereby eliminating any friction, and measured electronically to help confirm the calculation.

It's simple physics and not to be argued with. You can't fool Mother Nature with a concrete block behind the rifle butt.;)

JMHO

Ray
 
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Cheechako said:
Hatcher's tests were done with the rifle suspended on two wires, thereby eliminating any friction, and measured electronically to help confirm the calculation.

Ray
Click to expand...

I hadn't concidered the "reverse" Balistic Pendulum method this describes. I've made and used one of my own - of the "regular" type. Makes a fairly cheap and accuracte (if cumbersome) chronograph.
 
Vibe,
I concur with your calculations. And, assuming that you are correct, if the rifle tracks true and repetitively for the first .01" (or if you'd like a safety factor of ten, the first 0.1"), nothing that it does after that matters.
Hawkeye Wizard
 
Doug and Vibe,

I see Doug's point and it should prove or disprove Vibes calculations. I am reasonably sure that either of you could touch off the trigger without touching the rifle.

Warning: If Vibe's calculation on horsepower is right, which it isn't, the "cement" block will be pulverized to dust.

Concho Bill
 
A BIG thank you

To all the input it is greatly appreciated. The answer given has been a great help as it will assist me hopefully solve certain results.
Thanks to all Jim ( If there are any other comments please respond )
 
Bill Wynne said:
Doug and Vibe,

I see Doug's point and it should prove or disprove Vibes calculations. I am reasonably sure that either of you could touch off the trigger without touching the rifle.

Warning: If Vibe's calculation on horsepower is right, which it isn't, the "cement" block will be pulverized to dust.

Concho Bill
Click to expand...

have i said in the past that a computer is only as smart as the person putting info into it, and a phd makes a person book smart. commen since is so underated to somebody with a phd in bull$hit, and makes normal people so much smarter who use it.
 
I would trust Vibe's calculation on the recoil distance and Doug has an excellent test for Vibe's results. The horsepower comment that I made was just a private joke me and Vibe have going.

Vibe is working with known factors.

Concho Bill
 
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