British Artillery Range Table extract

[Sheldrake]

This is from RA XII Corps War Diary. They show the 50% zone and angles of decent for different equipment at different charges. The optimum for the 25 pdr is 9-11,000 yards charge 3.

[Carl Schwamberger]

Why is this optimum?

[Aber]

Text on right of table

"It will be seen that 25pdr Charge III gives the best combination of steep angle of descent and small 50% zone at about[7]000 to 11000 yards range"

Presumably steep angle of descent minimises variability in range - how to get densest concentration.

[Sheldrake]

Text on right of table

"It will be seen that 25pdr Charge III gives the best combination of steep angle of descent and small 50% zone at about[7]000 to 11000 yards range"

Presumably steep angle of descent minimises variability in range - how to get densest concentration.

Yes - but the angle of descent also matters too. The steeper angle of descent makes results in a better splinter pattern.

[Hoplophile]

I suspect that, in this instance, the word "optimum" means "highly suitable for a particular type of mission."

Given that the two characteristics mentioned are "steep angle of descent" and a "small 50% zone," the mission in question seems to be one in which the 25-pounders are shooting at relatively small target that is located behind various things that the British gunners wish to avoid hitting. (These might be friendly troops, terrain obstacles, or built-up areas.)

I would not be surprised if this document was created in the course of planning a creeping barrage, whether for an exercise or a battle.

[Sheldrake]

I suspect that, in this instance, the word "optimum" means "highly suitable for a particular type of mission."

Given that the two characteristics mentioned are "steep angle of descent" and a "small 50% zone," the mission in question seems to be one in which the 25-pounders are shooting at relatively small target that is located behind various things that the British gunners wish to avoid hitting. (These might be friendly troops, terrain obstacles, or built-up areas.)

I would not be surprised if this document was created in the course of planning a creeping barrage, whether for an exercise or a battle.

This is the dispersion pattern of splinters from a 25 Pdr shell with different angles of descent.


The 25 Pdr is not particularly effective as a means of destroyinga target. But a troop , battery, regiment or divisional artilelry group was a very effective way of neutralising an enemy in a 100 x 100, 150m x 150, 250 x 250 or 350 x 350m area, or as a standard, linear, concentration with 50 yards per gun - 525 yards for a regiment.

[Aber]

Yes - but the angle of descent also matters too. The steeper angle of descent makes results in a better splinter pattern.

Thanks - not something I knew before.

[Dave Humphreys]

Hi gents,
I'm looking at sites where 25 pounders were used and need a template as used back in 1945 era to determine where the rounds may have fell if fired from a particular point. Having trouble finding a representation of a safety template for the 25 pounder, well indeed all artillery, mortars etc from that era. DO you have any info you can share please?
Dave

[Sheldrake]

Not sure if I understand what you need.

I don't have the safety pamphlets from WW2 era artillery practices, but it may be able to construct what you need. They may have taken a more relaxed attitude to safety than in the modern world, but they must have applied something similar.

What sites are you looking at? Are you looking for the fall of shot from old artillery ranges, such as Alfristen?

[Sheldrake]

This isn't exactly right but is the kind of thinking I recall

Image a rectangular square impact area, 6,000yds x 6,000yds. We deploy a battery of guns half way along the base line, on the edge of the impact area.

We need to make sure that lethal splinters do not fall outside the impact area. So the safety distance needs to be 4 x PEr(100% zone) plus the extent that splinters from the ammunition will reach.

Looking at the 21 AG table 2 PEr at 6,000 yards is 40yds so 4 PEr is 80yds. The safe zone from splinters is 500-1000 yards depending on the ammunition, say 500 yards for 25 pounder. So the far end of the impact area needs to be reduced by 580yds for Charge II. A similar calculation needs to be applied at the forward edge of the Impact area. The left and right edges of the impact area will also need to be reduced. There may be some trigonometry involved to take account of the angle at which the gun will fire at each corner. However, for the 25 Pdr the PEr is small compared to the safe splinter distance, so it is going to be something close to 580 yds give or take 50 yards.

The reduced impact area for a 25 pdr charge 2 is going to be something like (6000 yds - 580 x 2) x (6000 yds - 580 x 2) = 4800yds x 4,800yds.

If we calculate the reduced impact area for a 7.2 Howitzer at charge 1, 2 PEr is 60yds, and the safe splinter distance will be much larger - say 1,000 yds. The reduced impact area will be a square (6,000 - 1,120 x 2) = 3,760 x 3,760 yds

It is more complicated for irregular shaped impact areas, and maybe an safety fudge factor is added but the calculations are something like this.

So most rounds will fall into the reduced impact areas.

[Carl Schwamberger]

This isn't exactly right but is the kind of thinking I recall ...

Close enough. I had to construct a entire set of firing area limits from scratch for a live fire exercise on Tinian Island in 1984. What fun. The fragmentation safety was one required component. PE alliance was required 'by the book' as well. In case a round falling at the maximum allowed range failed to detonate and "skipped" there was a extra maximum range safety buffer added, but only if the minimum elevation at maximum range was 270 mil or less. (Not very likely.) Wish I'd retained that set of charts a figures, wish I'd kept a lot of other firing docs from those days. Would be interesting to parse out now many of the details of old school manual gunnery.