Effective Range Mark VI Ammunition

[GregO]

Does any one know of ballistic tables for this ammunition? More specifically, how much does the bullet fall over 100, 200 & 300 yards?

[MikB]

Try here:-

https://forums.gunboards.com/showthread.php?127582-303-Mk-VI-ballistics

 

Scroll down about 3/4 of the way.

[GregO]

Great thanks. Does anyone know how variable the ammunition was cf Mark VII. Eg firing a machine gun. I know on that graph that shows the Mark VII trajectories for 700 yds, 25% of bullets will fall outside the 600-800yd range. Is there any equivalent info for Mark VI?

[MikB]

2 hours ago, GregO said:

Great thanks. Does anyone know how variable the ammunition was cf Mark VII. Eg firing a machine gun. I know on that graph that shows the Mark VII trajectories for 700 yds, 25% of bullets will fall outside the 600-800yd range. Is there any equivalent info for Mark VI?

Where does that come from? That variation seems excessive to me.

[Dave1418]

Hi 

I'd go back and have a good look over the graph on the link if that's what you're using and recheck the figures.

regards

Dave 

[GregO]

The Infantry Machine-Gun Company Training 1917 manual. Appendix A states the horizontal beaten zone to be at 75% 1.2 yds x 188 yds for Mark VII ammunition. ie 75 % of the time the bullet will land between 606yds and 794yds.

I am guessing the Army did a bunch of trials and counted a lot of bullets. Should be entirely due to small variations between bullets when fired from a fixed mounting.

The heavier slower Mark VI I would expect to be more variable.

Unless I have it all wrong....

 

Cheers

Greg

[MikB]

Rethinking this, I'm not saying it's wrong, but it might be misleading. I wonder if we've a nomenclature issue here. If the beaten zone is the intersection of the cone of fire with the ground, it runs from first graze to last graze; but the dangerous space, where a standing person will potentially be hit if the bearing intersects, runs from first catch to last graze. So an important determinant of the length of the dangerous space is the angle of descent. This is clearly steeper for Mk.VI than Mk.VII, and the distance between first catch and last graze will be shorter.

 

So far as I can see, Wikipedia (for example) seems to conflate what I think I was taught is dangerous space with beaten zone.

Or have I misunderstood what you're trying to say?

Edited 26 February , 2019 by MikB

[Dave1418]

Hi 

In addition to what Mik B has posted you also need to take into account the movement of the gun, and the downward gravitational pull, wind, temperature, etc etc. 

[GregO]

Thanks, the area on the ground where bullets land is the dispersion caused by minor manufacturing variations, a bit like drop shorts for artillery. Variability you don't know about until you fire it. The ballistics graph comparing Mark VI and MarkVII shows an average bullet's trajectory. I think in early 1917 they conduct a lot of trials on the statistical distribution of Mark VII ammo to find out how variable it actually is. Its broken up into 75% and 90% probabilities.

The machine gunners used this inherent variability to suppress fire via map references and compasses rather than first catch and last graze type of calculation. The area on the ground is also useful if you want to put a section of trench under fire, where the height of a man standing is irrelevant. The angle of descent is quite flat and doesn't really make a difference for how this is used, even at long ranges, at least it doesn't appear to be

I will assume it was unlikely anyone did such trials on Mk VI.

Thanks

Greg