How’s my physics?

[ChrisGreaves]

A regular rifle (.22, .303 etc) is placed upright on the ground, butt down, wedged into a pile of rocks, barrel pointing to the clouds.
Weather details are fed into a computer program which takes account of wind speeds, temperature and humidity, at various altitudes and computes a factor for air resistance, and hence an angle at which the rifle should be nudged within its pile of rocks (I would think only one or two degrees out of the vertical) to account for these factors.
The trigger is pulled, the bullet rises away from the earth, then falls back towards the earth.

Our hope is that the bullet will fall directly into the originating barrel.

I concede that the odds are remote, but suppose we had one of these exascale computers that could do the job, and we weren’t running it under Windows.
What factors other than weather (wind, temperature and humidity) should have been factored into the computer program?
I reason that rotation of the Earth is not a factor, since the rifle is already moving eastwards at the speed of rotation of the earth.
Chris

[HansV]

I wouldn't be surprised if the trajectory of the bullet becomes erratic/unpredictable at the top of its trajectory, because of its low speed there...

[BobH]

You would have to be able to control the trajectory of the descent because wind, atmospheric humidity and other factors are variable; therefore having read it before firing, one cannot assume that they will remain constant and probably a few million other reasons.

[PJ_in_FL]

IMHO, to be accurate enough to reenter the barrel, rotation of the earth and altitude of the rifle will need to be factored in. Consider the rifle VELOCITY (not speed, but instantaneous direction added in to make it a vector) is dependent on latitude and distance from center of the earth. As the bullet rises, the velocity component of it's movement imparted by the rifle is for a specific set of variables above, but the bullet's latitude and distance are changing as it's altitude changes. Note, latitude would probably not change for a bullet fired exactly at the equator.

Then there's also whether the sun is shining on the bullet (solar heating).

How much these factors affect the flight path is an exercise left up to the student.

[Leif]

What factors other than weather (wind, temperature and humidity) should have been factored into the computer program?

Earthquakes and off-course pigeons.

Oh, and did you want the bullet to return nose first or bottom first?

[Roderunner]

What factors other than weather (wind, temperature and humidity) should have been factored into the computer program?

Oh, and did you want the bullet to return nose first or bottom first?

If it fell bottom first, it would take longer as it's less aero-dynamic (streamlined).

[BobArch2]

You forgot to factor in one very important condition which negates all the others. The recoil action of the rifle when the bullet leaves the chamber.

Embedding the rifle in rocks is not going to make for a smooth exit of the bullet when fired.

During several years in army cadets and army reserves I have fired the Lee Enfield .303 rifle thousands of times on the target range with live ammo. I still remember the shoulder bruises when the web sling was not positioned correctly before pulling the trigger. Even the .22 rifle has a slight recoil.

I still have my marksmen badge from the 50's (but doubt I could earn it today! )

2017-08-05_13-52-58.jpg

[BobH]

[viking33]

Chris,
I think only you would want to take the time, energy, wonderment and effort, to set up the rifle like you theorize and then ask why the bullet didn't fall right back into the gun barrel!

[AlanMiller]

You might want to start simpler, with a blunderbuss firing a round ball



Maybe you could get it to drop back into the funnel. I'd hate to think of the external ballistics from a high velocity rifle in that situation. The bullet would have to slow to subsonic in its upward trajectory, with all sorts of drag/turbulence effects in the transonic regime, then fall to terminal velocity of around 200 mph on its downward path. The loss of stabilizing spin and the subsequent tumbling would be added complications. Let me know when you've figured it out!

Alan

[StuartR]

Just as a point of interest...

Lee Enfield rifles were made quite near where I live, in a factory by the River Lee in Enfield. The plant was originally built during the war with Napoleon.
https://en.wikipedia.org/wiki/Royal_Small_Arms_Factory

This factory was just down the river from the even older Royal Gunpowder Mills.

[BobArch2]

Just as a point of interest...

Lee Enfield rifles were made quite near where I live, in a factory by the River Lee in Enfield. The plant was originally built during the war with Napoleon.
https://en.wikipedia.org/wiki/Royal_Small_Arms_Factory

This factory was just down the river from the even older Royal Gunpowder Mills.

Stuart, thanks for sharing. Never knew the full history of the Lee Enfield rifle. While in cadets (1954-1958) we used the Lee Enfield indoors for drill purposes only. It was at army camps, Farnham and Valcartier, that we fired the Lee Enfield at outdoor ranges. We only knew that the Lee Enfields belonged to our Regiment (Black Watch) and were used during World War II. Your link provides a much better history of the weapon.

[StuartR]

I also fired Lee Enfield .303 rifles as a teenager Bob, and I remember the massive recoil and the bruised shoulder.

[AlanMiller]

While on interesting titbits, I recently learned that:

The venerable STEN gun is an acronym, from the names of the weapon's chief designers, Major Reginald V. Shepherd and Harold Turpin, and EN for Enfield.

Just so you know
Alan

[StuartR]

The STEN gun was another brilliant piece of engineering from the Royal Small Arms Factory, Alan.

[AlanMiller]

Indeed. And its "cleverness" was not limited to its engineering. With just two machined parts, well equipped sheds could be used as assembly factories. Pulled down, the bits could be hidden inconspicuously in scrap metal collections. And, of course, it was designed to fire captured German ammunition.

Alan

[viking33]

We carried around the 1903 Springfield in Navy Boot Camp. ( just to have something on our shoulder when marching around.) Never fired it
The standard issue was the M1 Garand and M1\2 carbine. Shot those a LOT.

[Jezza]

You forgot to factor in one very important condition which negates all the others. The recoil action of the rifle when the bullet leaves the chamber.

Embedding the rifle in rocks is not going to make for a smooth exit of the bullet when fired.

During several years in army cadets and army reserves I have fired the Lee Enfield .303 rifle thousands of times on the target range with live ammo. I still remember the shoulder bruises when the web sling was not positioned correctly before pulling the trigger. Even the .22 rifle has a slight recoil.

I still have my marksmen badge from the 50's (but doubt I could earn it today! )

2017-08-05_13-52-58.jpg

I remember the firing the Lee Enfield No. 4 Service Rifle .303 when I was a teenager in the cadets, I was a slip of a lad then and dreaded firing it but as I grew I became a dab hand at shooting it especially with the singer sight flipped up and could take on 200 yards easily having only one attempt at 400.

I remember the older kids used to tell the new ones to put their beret under their can jackets to help "stop" bruising not telling them to take the badge off. Uuuuurrgggh the bruises they got

[BobArch2]

I remember the older kids used to tell the new ones to put their beret under their can jackets to help "stop" bruising not telling them to take the badge off. Uuuuurrgggh the bruises they got

Cruel folks! Our beret (balmoral) sported the Red Hackle, no metal, so the balmoral would have been a good cushion. Mind you, we also wore the glengarry which sported the very large regimental badge. That would have hurt!

[DaveA]

The extra padding using the beret with the badge, is not to bad of a joke.
But while meeting the requirements for law enforcement, we had to fire the shot gun a few time. We had several in the group that had never fired a riffle let alone a shot gun.

So after the demonstrations on how it is to be done, some one suggested that if one was to hold the shot gun about a 1/2 of an inch from the socket of the shoulder it would not kick quick as much. Lease most of you do know the result of this.

Another step in this testing was firing the shotgun from the squatting position. Many were able to fire it OK, but ended up being flipped on to their back.

Yes this was a some what fun day for those of us the have been around fire arms most of our lives and forgot all of the tricks that were pulled on us when we were learning about guns.