calculating travel of a bullet

[Crater Creator]

The original poster was only interested in the gravity/velocity side of things I think, not the detailed ballistics calculations.....?
At 45 degrees trajectory, the equation is fairly simple because the horizontal and vertical velocity vectors are equal.
45 degrees (in theory) gives the furthest possible range.

 

[norlander]

BB has already hinted at how to get the answer. You brainy types do your calcs. Then pace out the distances you each come up with, stand in line, I'll fire the rifle at 45°.
The one that falls over is the winner-simple.

 

[Rudi McAnichal]

Rather than repeat a simple calculation over and over, can't you just use differentiation/integration?

Possibly, if you are clever enough. Ordinary mortals may find it quicker and easier to replicate the formulae in a spreadsheet.

According to wiki, the drag equation you mention only works for blunt objects with turbulence behind it.

Rifle bullets definitely involve turbulent flow – just look up Reynolds Number in any fluid mechanics textbook. The equation is not applicable for laminar flow, like those experiments where students drop ball bearings through thick oil in order to verify Stokes’ Law.

If you assume a drag coefficient of 0.1 you get a deceleration of 170ms^-2, it's got to be less than that surely?

Drag coefficient of 0.1 sounds rather low. I have a feeling that it could be several times higher than that for a bullet at supersonic speeds (the OP referred to muzzle velocity 3285ft/s).

As said previously, simple calculations can be used “if you assume drag coefficient to be constant.” That would be a reasonable assumption for Malcolm’s experiment with (subsonic) airgun pellets.

BB has already hinted at how to get the answer.

Agree totally, you cannot beat a practical test, because there are so many variables. More than half a century ago we were taught that a.303 Lee Enfield bullet could go way too high if just a few raindrops fell on the brass case, because reduced friction between case and chamber would alter the way the barrel vibrated.

Also, the practical test sounds much more fun than the maths.

Perhaps I should get somebody to check the sums for me. Bankers and economists have vast experience in making predictions based on mathematical modelling, so I might ask one of them for advice.

 

[Maker]

BB has already hinted at how to get the answer. You brainy types do your calcs. Then pace out the distances you each come up with, stand in line, I'll fire the rifle at 45°.
The one that falls over is the winner-simple.

Well I think I'll be alright at 63 miles.

 

[BrokenBiker]

Well I think I'll be alright at 63 miles.

i would hope so at least...

on a similar note i was out with a mate and a .222 yesterday and the one box of ammo he had said 2 miles on it. i cant see a .243 being much further than that to be honest

 

[brightspark]

i would hope so at least...

on a similar note i was out with a mate and a .222 yesterday and the one box of ammo he had said 2 miles on it. i cant see a .243 being much further than that to be honest

that's the distance it can travel and still poke someone with holdover

 

[norlander]

that's the distance it can travel and still poke someone with holdover

High velocity safety distance was at least 2 miles, ,it has to take into account ricochets, dead ground and stuff which I forget now (I used to do the safety templates for open field firing ranges-ie no backstops etc).

Irish Army sniper who kept missing- Corporal Rick O'Shea.

Get me coat.

 

[brightspark]

High velocity safety distance was at least 2 miles, ,it has to take into account ricochets, dead ground and stuff which I forget now (I used to do the safety templates for open field firing ranges-ie no backstops etc).

Irish Army sniper who kept missing- Corporal Rick O'Shea.

Get me coat.

tell me about it I hit a rabbit on a tarmac road . the bullet went strait through it richoched up and hit a house gable end 1/4 of a mile away lesson learnt that was a .22 subsonic

 

[norlander]

easily done, we had an old 600 yard range, proper butts, bullet stop etc. Local area was heather, sand and flint. They built a new housing estate, just outside the safe distance (less for a standard firing range).
The belt fed GPMG had replaced the Bren. It chewed up the sand bullet stop and the crest slipped down, some flints fell down along with it.
A 7.62 tracer fired from the 600 firing point ricoed off and somehow went through the bedroom wardrobe of one of the houses.
The range was then restricted to rifle only and 300 metres.They eventually gave up on it
There is an american police docu on youtube, some young lads nick a .22 (LR I presume) one of them fires it in a field on a ridge. Some bloke walking along the pavement in the town below was killed.
French hunters kill 6 people on average most years, I had to give our local ones the gypsy's warning after they fired with no stop towards dead ground, I was on the other side walking my pooch, being used to crack and thump, I clocked where they were, raced round and had a no coffee interview with em.

 

[hareng]

More than half a century ago we were taught that a.303 Lee Enfield bullet could go way too high if just a few raindrops fell on the brass case, because reduced friction between case and chamber would alter the way the barrel vibrated.

Equally it could have gone low, left or right unless projectile on any calibre was exiting at BDC, known about since start of last century called harmonics.

 

[Rudi McAnichal]

Equally it could have gone low, left or right unless projectile on any calibre was exiting at BDC, known about since start of last century called harmonics.

Explanation given was that a substantial portion of recoil force would be transmitted by friction to the chamber walls, provided the brass case was dry. If the brass was lubricated by moisture, more recoil would be transferred to the bolt head, and it would always cause the bullet go high. I cannot remember any more details. Nor did I ever see the effect for myself, because we always strove to protect the breech and ammunition from rain.

Is this still considered to be correct? The last time I fired a .303 was in 1964, and there must have been a tremendous amount of research over the past 50-odd years, so the current thinking might be quite different.

 

[mcostello]

Had a Grandpa that was a rough one. He was on a drive hunt in a big field with two opposing lines walking towards each other. Rules were only shots towards the open ends. A rabbit jumps out and fella opposite My Gpaw lets loose with a shotgun and misses. Hits My Gpaw in the knees, no harm done. Gpaw looks and sees He was hit and sends a round back at the Guy and peppers His legs. Emergency meeting in the middle of the field results in other Guy being tossed out and My Gpaw was declared right as the other Guy shot first and turn about was fair play. I'd a tossed them both.

 

[norlander]

Equally it could have gone low, left or right unless projectile on any calibre was exiting at BDC, known about since start of last century called harmonics.

On wet days on the range as firing point controller, I used to relieve the monotony by standing behind a firer and looking for the swirl caused by the spinning bullet passing thru the moisture (had to explain to commissoned officers not to do that in situations when someone at the other end is firng back ).
Never saw rounds going off on walkabout due to the wet to be honest.

Sorry lads, battles off, its raining or" why have the men stopped firng sarn't major" (Windsor Davies type sarn't major) "coz theys breeches is wet sah ".

 

[Cobbler]

On very wet days, are the bullets slowed much by hitting raindrops, or does it make no difference?

 

[norlander]

Only corrective tables for effects on trajectory of rounds are for wind (metreological not vindaloo fartulence), nothing for rain; artic or tropical heat. Gunnery, had FACE Field Artilley Computer Equipment, when I was in the mob, that took in allsorts of info and weather stuff to give the data to be fed to the guns.
Computers are fine but there is still Gunner Ackroyd on the gun, who managed to shell our trenches on Sussex Mountain, nearly spilt me tea (I said nearly- no dropshot oik is gonna make me ditch me brew)

 

[hareng]

Explanation given was that a substantial portion of recoil force would be transmitted by friction to the chamber walls, provided the brass case was dry. If the brass was lubricated by moisture, more recoil would be transferred to the bolt head, and it would always cause the bullet go high. I cannot remember any more details. Nor did I ever see the effect for myself, because we always strove to protect the breech and ammunition from rain.

Is this still considered to be correct?

Whatever the reason is for the cause the projectile is leaving muzzle at a different sonic signature. Barrels flex and whip.

 

[Rudi McAnichal]

Whatever the reason is for the cause the projectile is leaving muzzle at a different sonic signature. Barrels flex and whip.

You are certainly correct. I have no idea why were we told that raindrops on the brass make a bullet go high rather than low. The source might possibly have been Barlow’s “The elements of rifle shooting”, but my copy has long since vanished. It could have been just an “old wives’ tale”.

A quick web search reveals other reports about an effect on elevation, though it is not always clear whether the bullets would be going high or low.

‘... any water (even just one small drop) getting between the brass and the chamber will prevent the case from expanding to the dimension of the chamber. The knock-on effect could be increased pressure, a blown primer, change in muzzle velocity or change in POI on the target.
I've seen the effects during one very wet day at Bisley when I tried my best to keep the rounds and chamber dry but found that a tiny amount of water made a big difference on the target even at 300 yds.’ http://ukvarminting.com/forums/topic/20565-bullets-and-the-rain/

‘... if you were shooting something like a Lee Enfield, that action is extremely flexible with its rear locking lugs. The Brits reported elevation changes due to "wet" versus "dry" cases.’ https://thefiringline.com/forums/archive/index.php?t-427839.html

‘... above all - keep your ammo dry. Among other downfalls, wet ammo will give you elevation shots.’ http://www.vra.asn.au/documents/FClassTargetShootingTechniquesTrainingCourse.pdf

‘Wet or oily ammunition will cause an increase in chamber pressure. At worst this will cause an explosion or bulge in the barrel, leading to a loss of accuracy in the weapon. At the very least it will result in increased muzzle velocity, thereby raising the MPI on the target.’ (Mark Spicer, Illustrated Manual of Sniper Skills)

 

[thinfourth]

How would the bullet travel be effected if you put the renault megane in its path?

 

[slim_boy_fat]

^^ Remember the TG programme when they killed a BMW with a machine gun?

 

[slim_boy_fat]

BB has already hinted at how to get the answer. You brainy types do your calcs. Then pace out the distances you each come up with, stand in line, I'll fire the rifle at 45°.
The one that falls over is the winner-simple.

Do we have a 'last man standing' yet?