Barrel temperature

[Koda]

It's not just gravity, but the arc of the bullet path after it leaves the barrel.

Archery hunters learn this quickly when you sail an arrow aver a deer because you held too high on a downhill slope.

isnt that because they calculated the hypotenuse not the horizontal distance? IOW, downhill shots appear much farther away than they actually are, no different than the horizontal distance.

 

[Greenbug]

He said he is using a laser rangefinder that compensates for angle and gives the true horizontal range. With that equipment the angle should not matter just the effect of gravity over the horizontal distance.

I get the archery reference but that is using set (horizontal distance) aiming pins. Archers are not typically adjusting their pins before a shot like a rifle shooter might be doing with scope adjustments.

 

[Ura-Ki]

Explain to us how the effect of gravity changes depending on if your barrel is pointed uphill or downhill.

This should be good.

All right then SMART ARSE!
Get ready for some science!

How To Shoot Downhill and Uphill: Bullet Trajectory - RifleShooter

Making precise hits when shooting downhill and uphill has morphed from dark wizardry to science over the past several decades. Here is what you need to know to account for angled shooting.

www.rifleshootermag.com

 

[Nosferatu]

isnt that because they calculated the hypotenuse not the horizontal distance? IOW, downhill shots appear much farther away than they actually are, no different than the horizontal distance.

That's part of it, but a heavier, slower moving arrow drops much faster than a lighter, faster bullet.

 

[Kruel J]

Your on the right track with this!
Several things are happening to your rifle in the field, The Ambient temp will be your "Cold Bore" and all else being equal, should align POI/POA with how you zeroed it. As temps go up, the metal expands slightly ( VERY SLIGHTLY) and velocities can increase, ( Slightly) mostly due to the air temps and even altitude! As the barrel heats up through additional shots, it's going to loosen up even more, this time noticeable, this is why you see its groups opening up some, even sending flyers! the opposite happens in very cold temps, the barrel will hold POI/POA longer, but may shift the cold bore results a little! As bad as that is, your ammo is even more sensitive, cold temps can make your ammo "Lazy" partly due to the slower burn ( Getting up to temp in the chamber) and denser air which is thicker! In high heat, and especially at higher altitudes ( Density Altitude) the shots can pick up a couple hundred feet per second, and that can also change the POI/POA signiffigently! his is why you see marksmen setting their ammo out in the sun to heat it up as it can both increase the effective range, and velocities! The heavier the barrel contour, the more mass that any heat must overcome or equalize, and that's why you see varmint rifles, and even some big mage rifles wearing bull barrels! We used to have to "Math it out" in the service to determine if there would be any changes and through experience with the rifle, generally knew what changes to expect and what dope to hold or dial in! Pretty cool stuff to witness, especially when the air density is way up and there is lots of humidity, you can actually see the bullet's track as its shock wave pushes the vapers out of the air and makes the visible swirl!

Excellent response.

 

[Hueco]

This is why you see marksmen setting their ammo out in the sun to heat it up as it can both increase the effective range, and velocities!

This is why I keep my ammo in my underpants. Keep your bullets next to your gun and they'll be toasty warm for your rifle, regardless of outside temp.

Yea it's a little uncomfortable single shot loading from prone…but extreme accuracy requires extreme sacrifice.

 

[Ura-Ki]

This is why I keep my ammo in my underpants. Keep your bullets next to your gun and they'll be toasty warm for your rifle, regardless of outside temp.

Yea it's a little uncomfortable single shot loading from prone…but extreme accuracy requires extreme sacrifice.

No Joke, this can make all the difference in very cold conditions!

 

[Greenbug]

All right then SMART ARSE!
Get ready for some science!

How To Shoot Downhill and Uphill: Bullet Trajectory - RifleShooter

Making precise hits when shooting downhill and uphill has morphed from dark wizardry to science over the past several decades. Here is what you need to know to account for angled shooting.

www.rifleshootermag.com

This explains it pretty well, you should read it so you understand.

 

[Koda]

Get ready for some science!
https://www.rifleshootermag.com/editorial/hitting-a-high-or-low-angle-shot/83768

actually, your article validates what Ive read a while ago. Holdover is a matter of true horizontal distance not angle.
(scroll down to TBR...)

 

[Ura-Ki]

This explains it pretty well, you should read it so you understand.

UH, OK!
I understand it just fine thank you!

 

[Nosferatu]

This explains it pretty well, you should read it so you understand.

There's no need for that nonsense. Ura-Ki has earned some respect for his experience around here. Some of us have yet to deposit the same amount of piss in the bucket.

 

[Ura-Ki]

actually, your article validates what Ive read a while ago. Holdover is a matter of true horizontal distance not angle.
(scroll down to TBR...)

YUP, but Note how it changes as degrees changes!

 

[Mark W.]

As far as ambient temp changes go.


Instead of going at this from some sort of theoretical puzzle its simple. Sight in your rifle on a day where the temp starts out at say 70° then do the same with the same ammo at the same range on the same day when the temp hits 80° then at 90° then 100° and with 12 rounds you will know exactly what YOU and your rifle will do group and POA wise due to the temp change.

Oh and all those guys that knocked down deer antelope elk at 200 yards Standing with a Winchester/Marlin/Savage carbine in 30-30 with open iron sights are laughing their heads off.

 

[Koda]

YUP, but Note how it changes as degrees changes!

I did notice that, but I hope to never hunt in 65degree terrain...
I think whats happening here is everyone is looking at the same solution from different angles (no pun intended but hey). I can guess that maybe at extreme angles overtakes the simplicity of true horizontal distance? Further down your article it tells how to manually calculate for the angle to get true horizontal distance... I will have to stick to my LRF.

 

[Koda]

As far as ambient temp changes go.


Instead of going at this from some sort of theoretical puzzle its simple. Sight in your rifle on a day where the temp starts out at say 70° then do the same with the same ammo at the same range on the same day when the temp hits 80° then at 90° then 100° and with 12 rounds you will know exactly what YOU and your rifle will do group and POA wise due to the temp change.

Oh and all those guys that knocked down deer antelope elk at 200 yards Standing with a Winchester/Marlin/Savage carbine in 30-30 with open iron sights are laughing their heads off.

I actually discovered this last summer, when on a very hot day my zero was actually off enough to warrant adjusting. I had zeroed last in the fall on a rather cooler fall day. Been going down the rabbit hole on this since...

 

[Flopsweat]

I actually discovered this last summer, when on a very hot day my zero was actually off enough to warrant adjusting. I had zeroed last in the fall on a rather cooler fall day. Been going down the rabbit hole on this since...

Well shooting down rabbit holes is easy. No holdover. I don't even use the sights.

 

[Ura-Ki]

Well shooting down rabbit holes is easy. No holdover. I don't even use the sights.

Easier then shooting fish in a barrel with a howitzer!

 

[Flopsweat]

Easier then shooting fish in a barrel with a howitzer!

Shorter stand-off too.