Long Lee Enfield accuracy vs the MKVII cartridge?

[rayg]

Just curious, in as much as the MKVII cartridges velocity is approx 2500 fps and considerable more then the 2000 fps the Long Lee Enfield was designed for. What impact would a MKVII rd have on the point of aim of a Long Lee Enfield that was sighed in at 100 yrds with the older rd?. Would the MKVII shoot higher or lower and would it change windage like shooting more left or right of center because of the faster bullet? Ray

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[bradtx]

rayg, When the Mk.VII was in the process of selection there was also found that the forcing cone needed to be modified slightly to improve accuracy.

I have no idea how badly it'll shoot, maybe there'll be no difference, but I'd expect some accuracy degradation. Let us know.

Brad

[Fred G.]

What's a forcing cone? Oh, OK, I looked it up. Never mind.

[rayg]

Hi Brad, not so interested in accuracy but the difference in bullet impact between the two cartridges. As I understand, a slower heavier bullet would impact higher at 100 yrds then a lighter faster bullet. So a MKVII bullet would shoot/strike lower then a rifle sighted in at 100 yrds with the older heavier bullet. Now what about windage. The Enfields have a right hand rifling twist. Would a faster bullet effect bullet impact/strike more left or more right then the slower heavier bullet, or would there be no change? Ray.

[Fred G.]

Hi Brad, not so interested in accuracy but the difference in bullet impact between the two cartridges. As I understand, a slower heavier bullet would impact higher at 100 yrds then a lighter faster bullet. So a MKVII bullet would shoot/strike lower then a rifle sighted in at 100 yrds with the older heavier bullet. Now what about windage. The Enfields have a right hand rifling twist. Would a faster bullet effect bullet impact/strike more left or more right then the slower heavier bullet, or would there be no change? Ray.

Enfields have a left hand twist. Higher velocity ammo from my experience will hit higher.

[rayg]

Oops you're right Fred, got it mixed up, Ray

[bradtx]

Ray, In that context, a very interesting question regarding the windage aspect. I can't wait for the ballistic guru's responses.

Brad

[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