More BBC bs - Britains Next Air Disaster

[KB1]

6 minutes ago, Rewulf said:

If you are good at maths, you can work that one out !

I am good at maths, but know little or nothing about the procedures for calculating ballistics…….   But at this moment in time I'm faced with a trained sniper saying one thing, and dear old Rewulf saying another🤔  forgive me if I don't take what your saying at face value.   All interesting stuff though👍

[Rewulf]

10 minutes ago, KB1 said:

Im still digging😀

.375 Cheytec in the video 8000ft ilb ME at 3000 fps , 400 gr bullet.
Sits between the .338 LM and .50 BMG

As you can see , they are achieving these shots by firing from an elevated position, down onto the target, so its kind of cheating on the power front, but otherwise it would require that much elevation the user wouldnt be able to see the target.
Good shooting though , especially in that wind, helped by the phenomenal BC of the .375 bullet.

5 minutes ago, KB1 said:

I am good at maths, but know little or nothing about the procedures for calculating ballistics…….   But at this moment in time I'm faced with a trained sniper saying one thing, and dear old Rewulf saying another🤔  forgive me if I don't take what your saying at face value.   All interesting stuff though👍

How do you know Im not a trained sniper ? 😎

[KB1]

51 minutes ago, Rewulf said:

How do you know Im not a trained sniper ? 😎

Because your a Brexiteer😀  Only Remoaners snipe…..

[TIGHTCHOKE]

54 minutes ago, Rewulf said:

.375 Cheytec in the video 8000ft ilb ME at 3000 fps , 400 gr bullet.
Sits between the .338 LM and .50 BMG

As you can see , they are achieving these shots by firing from an elevated position, down onto the target, so its kind of cheating on the power front, but otherwise it would require that much elevation the user wouldnt be able to see the target.
Good shooting though , especially in that wind, helped by the phenomenal BC of the .375 bullet.

How do you know Im not a trained sniper? 😎

 

2 minutes ago, KB1 said:

Because your a Brexiteer😀  Only Remoaners snipe…..

Brilliant retort!

[Rewulf]

1 hour ago, KB1 said:

Because your a Brexiteer😀  Only Remoaners snipe…..

I'll take that 😂

[chrisjpainter]

So. Aldo Kane got the distances wrong. Other than that, what did people think? 

[Vince Green]

13 hours ago, Rewulf said:

Ill add to this from my limited knowledge of ballistics.

When a projectile of a given weight loses enough speed/energy, it de stabilises , this causes it to 'tumble'
Once it starts doing that it loses virtually ALL of its aerodynamic efficiency ( BC )
At this point  gravity has more effect and it falls to earth rapidly, the heavier the projectile , and higher the muzzle velocity , the longer it will stay stable.

Even a .50 BMG round cannot achieve 10 mile range.

A rifle bullet travelling at 3000 fps fired from a 1in 12 " barrel is rotating at 3000 revs per second which is 180,000 rpm! A bullet loses forward velocity very quickly and much more quickly than it loses rotational velocity which it hardly loses at all.

So here is the strange but true bit. A bullet is not nose heavy like an arrow or a dart would be, and, because it is rotating so quickly, it doesn't turn over at the top of its travel to start decending nose first as an arrow or dart would.

A bullet fired up into the air at 45 degrees spends the whole of its flight travelling at the same 45 degrees relative to the ground as when it was fired. That's mainly because it is still spinning so fast relative to its forward velocity. (Gyroscopic effect)

That means it starts coming down sideways and that creates much more air resistance and it slows even faster. That's where these ballistic programmes depart from reality. They predict by calculation and assume the BC remains constant but their calculations don't take into account the sideways effect and ever increasing air resistance.

This was first identified by an American called Earl Narramore whose job was to develop elevation tables for American field cannons at Aberdeen Proving Ground in America in the 1920s. He was able to establish why the cannons didn't achieve  the calculated range predicted for them, He established that at extreme range the shells were falling base first into the ground still spinning very fast. He painted the shells and the scratches on the paint proved his point.

Heavier bullets still have the same front on cross sectional area as a lighter bullet so the ballistic coefficient is always going to be better on the way up, but, for reasons stated above, once they top out they fail even quicker because the side on area is greater. At 1200 yds a 7.62 bullet cuts a slightly oval hole in the target.

Part of the reason why so many shells did not go off in the first world war was because they were landing base first at extreme range and not triggering the detonator in the nose. Many of the recovered shells, still being dug up every year have undamaged brass nose fuses. Which is handy for the idiots who try to salvage them for keepsakes..  

 

Edited July 5, 2019 by Vince Green

[TIGHTCHOKE]

Thoroughly enjoying this thread!

[Jay_Russell]

from memory when we did a joint exercise with the usm i was rather interested in the .50cal sniper rifle they were showing off with, i seam to recall in the briefing the max range of the .50cal was something like 7000yds - efftective range was 2000yds 

[Rewulf]

40 minutes ago, Jay_Russell said:

from memory when we did a joint exercise with the usm i was rather interested in the .50cal sniper rifle they were showing off with, i seam to recall in the briefing the max range of the .50cal was something like 7000yds - efftective range was 2000yds 

7000 yards is roughly 4 miles, I think with the correct (optimum) elevation it would go a bit further for .50 BMG..
Effective range is subjective, depending on what the reason for the shot is, if you intend to kill the target, then 2000 yards (just over a mile) seems more than adequate, however...

http://www.bbc.co.uk/newsbeat/article/40381047/a-canadian-sniper-breaks-the-record-for-the-longest-confirmed-kill-shot---but-how

A confirmed kill at 2+ miles takes the record, again, from an elevated position, which makes it possible to 'see' the target without a special scope mount.
Compensating for bullet drop at these sort of ranges would run a normal scopes limits of adjustment out on the flat.

[Rewulf]

If you use Gundatas ballistic calculator and set up a .308 Winchester at a 45 degree angle, you end up with a graph like this .

Its worth noting that after 2500 yards it has lost stability, its energy has dropped to around 100 ft lbs , and is dropping like a stone to hit he ground at 3500 yards with around 20 ft lbs.
As I said , 45 degrees is not optimum angle.

This time with 30 degree angle it travels further.

http://gundata.org/ballistic-calculator/

[English]

If you do the NRA probationary membership this is one of the questions they ask related specifically to 7.62 or .308 Winchester at approx. 30 degrees elevation they say a 7.62 / .308 will have max travel of 2,5mile or 4000m