ID guns on these MCC trucks

[Lang]

MikeC,

Good info as usual.

I think your info on reducing the range with elevation is suspect - you can't beat physics - 45deg is maximum range for any projectile, thrown rock, motorcycle jumping busses or garden hose. Shot-put and javelin athletes aim for an exact 45deg launch.

I seem to remember "howitzer" referred to a weapon capable of higher angles than 45deg - very useful for high crest clearance or tossing over a hill ie the shells go further and further as the gun gets to 45deg then start coming back in - try it with a garden hose. In theory, if you can get it high enough (mortars have no trouble) you can drop a shell down almost vertical behind a building 100 metres away - or maybe back down your own barrel!.

They had a reasonable range because they had quite a good muzzle velocity. For those whose memory needs jogging like mine these days, the weight of the projectile has absolutely nothing to do with its range. If we had a target at 100 metres a 22 aimed direct would hit it about 5 inches low, a heavier 243 would hit it about 1 inch low and an even heavier 18 pounder would hit it about 8 inches low. It is all to do with the time in the air while gravity is pulling them all down at 32 ft/sec/sec so velocity is king.

I can't figure out why they only had 16deg unless they were designed as a direct fire weapon - it would make them almost useless as an indirect fire support weapon. Any ideas? I suppose they came from an era where the commander still stood on a hill and directed the battle visually.

[Lang]

Just done a bit more research on the 18 pounder. The Kiwis were certainly sold a pup if they bought those early guns. Maybe they are an anti-tank unit?????

They were designed as a direct fire weapon and obviously upgraded to indirect fire as better sights were invented during the post Boer War period (quite amusingly the Brits chose a German manufacturer to make their sights). During WW1 they were soon upgraded to 30deg elevation and then 37deg as mentioned above by redesigning the trail..

I think the Kiwi buying committee were misunderstood by the Brits when they ordered guns for 'ndrct' fire.

[Mike Cecil]

That gave me a laugh, Lang!

I agree that velocity is 'king', and I don't think I was specific in mentioning the angle at which the fall of shot starts moving back: but I believe what I said was correct as stated.

Now take the 18pdr's successor, the 25-pdr, described as a 'gun-howitzer'. Although its max angle of elevation on carriages Mk.1 and 2 (and sub variants) was less than 45 degrees (actually a max of 40 degrees with spade embedded), the fall of shot could be varied by another factor: varying the charge weight (it was a semi-fixed cartridge), hence, varying the velocity. The combination of those two factors gave the weapon much greater flexibility: everything from 'lobbing' shells over tall hills at low velocity (indirect fire) to firing anti-tank shot direct on Charge Super (at max velocity). The Mk.3 carriage gave even greater ability to clear crests, being articulated to give an even greater max elevation well over 45 degrees.

Mike C

[RHClarke]

Gunners have never been constrained in the use of their field pieces by engineering/manufacturing specifications. Fixed max elevation on 18 Pounders and 25 pounders were overcame by digging in the trails (http://books.google.ca/books?id=oLge...g%20in&f=false see image at page 38). This changed the maximum ordinance or max height of a round and its overall range. The data for exceeding max elevation could not be found in its firing tables, but the fall of shot would be consistant making adjustment of artillery fire at high angle a reality.

Modern day howitzers (towed or tracked) have a greater ability to engage targets in "high angle" or in the "upper register" than their predecessors, but if you absolutley had to engage a target close to the gun position but hidden behind a high obstacle, you need only to request fire from another call sign (arty, armoured, attack helicopter or if they check out of the Holiday Inn on time, fast air support) that can reach out and touch the target.

[Lang]

MikeC,

I think most people are right when they praise the 25 pounder, which I understand used the 18 pounder as a basis for design.

The different charges were very convenient for range/approach angle variation. When I was a 17 year old kid in 11 Field Regiment they also said they liked to use minimum charge to reach the target to reduce barrel wear. As kids, we all loved to be the ones who burned the big heap of extra charge bags at the end of a shoot.

I used to hate it when they called out "Charge Super" (which was rare). When you pulled on the handle it was like being wacked over the head with a baseball bat. I saw stars every time!

As an aside, I would like to know where the higher angle/less range (below 45deg) theory comes from, I think it can't happen.

Lang

[Mike Cecil]

Lang,

To clarify, I didn't say that the 'higher angle/less range' could happen at less than 45 degrees. I simply stated that, for a fixed cartridge like the 18pdr, there comes a POINT where further increases in elevation cause a decrease in range. You later specified this to be 45 degrees, with which, all things being equal, I agree.

Mike C

[Local Chap]

Originally Posted by Mike Cecil

Lang,

To clarify, I didn't say that the 'higher angle/less range' could happen at less than 45 degrees. I simply stated that, for a fixed cartridge like the 18pdr, there comes a POINT where further increases in elevation cause a decrease in range. You later specified this to be 45 degrees, with which, all things being equal, I agree.

Mike C

The range of a artillery projectile is primarily dependant on the Muzzle Velocity, rather than the ammunition type being fixed or semi-fixed. The 4.7in AA gun (aka 28pdr) has a greater range than the 25pdr, and uses fixed ammunition. There are at least 2 recorded instances in the Aust Army during WW2 where 4.7in guns were used as field guns at a range beyond the 25pdr's (Milne Bay and Morotai). It did involve some co-operation between the crews, with Fd Gunners setting the fuzes and the AA Gunners calculating ranges and time of flight. The point that Mike has made is that the Semi-Fixed type offers far greater flexibility in controlling MV.

All guns have range tables that show range for elevation. For fixed types, this is a simple chart that shows elevation x = range y (with other variable calculations for bore wear, temperature, altitudes and in some cases windspeed!). For the 25pdr and 105mm (both of which use semi-fixed ammuntion), there is a separate range table for each charge (25pdr has Charge 1, C2, C3 and Super Charge, while 105mm has C1, C2, C3, C4, C5, C6, C7 and Super), and again each one is affected by variables. The 25pdr has effective range from 100yds on Charge One at zero deg to 13,900yds at 45 deg on Super for a gun in peak condition on a cool day at low altitude. For a gun with a worn bore, on a hot day at high altitude (all factors which affect MV), the max range drops to 12.300yds!

Interestingly, the table for 4.7in AA gives a maximum range of 20,600yds at 46 deg