Long Lee Enfield accuracy vs the MKVII cartridge?

[rayg]

Thanks Fred, interesting. My rifle with the * on the sight shoots dead center with the MKVII ammo. It has no provsion for the cleaning rod so it was upgraded. My other all matching one with the blade offset to the left, shoots 3-4" right of center. It looks like if that blade was moved to the center like the one with the star, it would shoot more center also with the MKVII ammo. That sight has no * so I'm assuming it was not modified and was still sighted in for the heavier slower bullet? Ray

[Fred G.]

Ray, what is the year of manufacture of the Mk I* rifle whose front sight has the * ? If it has no provision for the rod and has a solid stock and was made after May of 1899, then it has no upgrades. It was made like it is at the armory. The rifle was suitable for the ammo that they were using at the time of the rifle's manufacture. The other rifle was never upgraded and was probably not used with the later ammo. I wonder if my Mk I* would shoot accurately with Mk VII ammo too? It being made in 1900 was also made without any provision for a rod and the sights are accordingly suited for the later ammo. The star on its front sight base is not an * but is actually a six pointed star.

[rayg]

Fred, the rifle with the starred sight is dated 1896 but has been upgraded. If the front blade on your rifle is centered, it probably should shoot center.

Apparently the blades on the front sights were originally offset to the left to compensate/allow for bullet drift to the left. I assume that's why the blade on my un-modified on is set to the left which in turn makes you shoot more right at close distance but the bullet would drift closer to center at a further distance.

I wonder at what distance would the bullet shoot center if the rifle is shooting 3-4" right at 100 yrd, Ray

[Alan de Enfield]

I seem to remember (a long time ago) that there was a discussion on another forum about long distance shooting and the correolis effect.

This being that once the bullet has left the rifle it is in free-space but the Earth continues to rotate, at distances around 1000 yards the target is 'nowhere' near where it was.

This applies if Shooting Due North or Due South.
If shooting Northwards the bullet will impact to the East and if shooting Soutwards the bullet impacts to the West.

The correolis effect is calculated as
Y = 2wVsin (latitude)

W = Earths rotaion (0.0000729 degrees per second)
V = Bullet speed

Example at 45 degrees North and a bullet speed of 2800 fps the equation gives 0.3fp second per second
At 350 yards you'll get about 1/2" displacement
As a rough guide for longer distances use 1" correction for each second of flight time.

Throw in the wind effect over 1000 yards and it becomes a tad more tricky to calculate.

Hunter's Guide to Long-Range Shooting - Google Books

[Fred G.]

I thought that only applied to artillery. Holy Crap! I allways figured that it was the direction of the rifling that made the bullet veer left or right. The 1903 Springfield twists one RIGHT turn every 10" and will drift to the right. The Enfield one LEFT turn every 10" and will drift to the left. The bullet is dropping as it flies and at 2700 FPS or so, I thought the spin of the bullet actually rolled the bullet in the direction of the spin because the greater preasure against the bullet, besides the tip, was to the bottom where the bullet was starting to fall while still maintaining it's original line of axis when it left the muzzle. Kind of like rolling on the surface of water. Whew! It's all very complicated to me!

[JBS]

There are two effects. Coreolis effect is the movement of the earth while the bullet is in free flight. Magnus effect is the rotational effect of the bullet acting on the fluid ( air ) it is traveling in and depending on the deflection of the bullet nose and center of rotational mass causes the bullet drift not attributed to wind or air movement.

[Fred G.]

Yep. the 1903 Springfield sight and the Krag's 1901 sight automaticly adjusted for this "lateral drift" as the range increased. The Enfield's rear sight did not.

[Alan de Enfield]

From SEAL Sniper Training Program 1992
Temperature differences between the rifle and target have an effect as well.

"Mirage also has a density in addition to direction :
Thick density
High temperature or
High Humidity or
Bright light

Thin Density
Low temperature or
Low light

At 1000 metres (1100 yards) a 10 degree change in temperature necessitates a +1 minute of angle adjustment (thats 11" at 1100 yards)

Elevation above sea level also has an important effect on bullet trajectories. At higher elevations, both air density and temperature decreases, and air drag decreases. At higher elevations the sniper tends to shoot high".

Summary - before taking the shot you need to know :
Direction of shot (North, South, East, West) (Coreolis effect)
Direction of bullet rotation (Magnus effect)
Wind strength & Mirage effect
Elevation
Temperature

[JBS]

Or if one is using minute of Duce and a Half ( 2.5 ton truck ) Kentucky windage and elevation will work.

[rayg]

There are two effects. Coreolis effect is the movement of the earth while the bullet is in free flight. Magnus effect is the rotational effect of the bullet acting on the fluid ( air ) it is traveling in and depending on the deflection of the bullet nose and center of rotational mass causes the bullet drift not attributed to wind or air movement.

Boy lots of things effect the bullet in flight, temp, air, earth rotation, and bullet spin.

During the last wars, it was found that most shots were taken under 300 yrs, even for snipers. So a lot of those effects are not really relevent today except for long range snipers and target shooters.
Back to my original question as I'm really curious. If my rifle shoots 3-4" right at 100 yrds, how far out would the
Magnus effect effect bring it center target. I'm thinking maybe 500 yrds? I'm only saying that because that's what the longist yard position that the base sight in the down position can be adjusted to. Ray