Mechanization

[davebender]

That would be useless for direct fire and the 18 pounder shell is too small for effective indirect fire. You would be further ahead to install an inexpensive 120mm mortar on an outdated tank chassis.

[Shortround6]

Yes it would be useless for direct fire but if you are using the divisional artillery assets for direct fire the situation has gone to pot in a big way and total disaster is imminent.

The M7 Priest and the Sexton were never intended for the direct fire role. Like wise the US M37 self propelled 105 was never intended for the direct fire role nor the post war M-108. The M-12 155mm was only intended for the direct fire role in the rarest of circumstances, as was the M-40. The M-55 and M-109s are not direct fire weapons. The M-41 was not a direct fire weapon.

As far as further ahead????

The 18pdr could range to 11,000yds with 38 degrees of elevation, given an observer in a good position (or aerial) it could sit thousands of yards out of range of the 120mm mortar and pound it to destruction.

If you want rebore/reline the the gun to take 25pdr ammunition as was done to around 1000 towed guns, not quite the range of a regular 25pdr (due to elevation limit) but th e traverse of the 18pdr MK V mount may make up for it.

18pdr HE shells of WW II weighed 18.5 lbs and carried 1.1 lbs of explosive. While not 105 howitzer rounds they are a step above 75mm rounds.

Your a bit too obsessed with cheap weapons. Cheap is good in some cases but carried too far results in the loss of capability. Russians equipped entire battalions with stamped sheet metal sub-machine guns and hand grenades, worked in cities and in the open with lots of t-34 tanks as close support. In the open without the tanks???
How much do the tanks cost in relation to the "normal" battalions heavy weapons?

Somebody once claimed the Germans would run from "cold steel" (bayonet charge) on the Russian front. A cynic replied they only ran after the machine gun ran out of ammunition.
Bayonets are really cheap. Machine guns are expensive. We know how most armies wound up voting.

[davebender]

If you are going to that trouble why not just develop a modern 105mm light howitzer?

[Shortround6]

Just maybe because were talking about the British army before WW II. Developing special guns "just" for the mechanized troops that took different ammo was a luxury nobody could afford.

The British did rebore/reline 1422 18pdrs to 25pdrs from 1937 to1941 while production of the "modern" 25pdr was organized and under taken, First "modern" 25pdr being made in 1940.

[tomo pauk]

Tomo, a more "practical" SP gun for 1938-39 would be to take the A9, and much like the Archer 17pdr, turn it around so that the gun is pointed back over the engine deck. Use the 18pdr MK V Mount so you have 25 degrees traverse each way (or within vehicle limits) without moving the vehicle. 8 degrees of traverse is a joke. Now you have the room from the turret and mg turrets (and driver vacating his seat) for the gun crew to work. Much more room than a MK IV light tank lashup. More ammo on the vehicle.
When the Germans were converting those left over British and French chassis, not only did they not have enough tracked chassis of their own, or trucks, they didn't even have enough horses go around. Any way of moving a gun was an improvement over not moving it.
Much artillery fire is not done at the maximum rate of fire but limiting your peak rate of fire because of a too small vehicle is a problem that CAN be avoided in peace time.

I have a vehicle like you're describing on the pipeline, it would not take much for the British to come out with one
IIRC the cause for artillery not firing on max rate was the barrel's imminent overheating, after a minute or two of firing at max rate?

While the entire ammunition supply doesn't need the same mobility as the guns there is usually a lot more ammunition than people think. In 1914 the "official" ammo supply for an 18pdr gun was 24 rounds on the gun limber, 152 rounds on ammo wagons in the battery, 76 rounds in the Brigade ammunition column, 126 rounds in the Division ammunition column for a total of 378 rounds on transport. A further 150 rounds were in Divisional ammunition parks and another 472 rounds in ordnance depots. These was supposed to be the allotment per gun in the field and not including storage in home depots or factories. How close they came I have no idea and a number of revisions happened as to what ammo was kept were as the war went on.

Thanks; as they say, logistics is the key

[davebender]

Developing special guns "just" for the mechanized troops that took different ammo was a luxury nobody could afford.

The mechanized chassis costs a lot more then a 105mm howtizer. If Britain cannot afford to purchase light howitzers then how are they supposed to purchase SP artillery of any type?

Price examples.
16,400 RM. 10.5cm leFH18 howitzer.
22,000 RM. Sd.Kfz.11 towing tractor. Normal tow vehicle for a 10.5cm howitzer.
about 50,000 RM. Panzer II. The smallest possible chassis that can carry a 10.5cm howitzer.

[Shortround6]

British had been working on the 25pdr for a number of years. They weren't going to adopt a 105 howitzer in 1938-1940 no matter what.

[Shortround6]

I have a vehicle like you're describing on the pipeline, it would not take much for the British to come out with one
IIRC the cause for artillery not firing on max rate was the barrel's imminent overheating, after a minute or two of firing at max rate?

For the 25pdr the firing rates were

Rates of fire---------Gunfire------Intense------Rapid------Normal--------Slow--------Very slow

Rounds/Minute------6 to 8---------5------------4----------3------------2--------------1

I haven't found the firing rate/s for the 18pdr yet but I would be very surprised if it was under 12 rounds a minute for it's max rate of fire and may have been as high as 15-20rpm with prepared (fused) ammunition. Shell was crimped to cartridge case so one piece loading with no charge adjustment.

A US 105 howitzer was supposed to do 8rpm for the first 1/2 minute, 4 rpm for 4 minutes, 3 rpm for 10 minutes and 100 rounds an hour. If the crew has time to prepare ammo and lay it out (zone charges adjusted and shells fused) then having a single loader ammo handler might not be too bad, depending on far from the gun breech the rounds are after the first 10 or so. That is assuming they want 25-30 fused shells laying about. If fuses have to be fitted and zone charges adjusted while firing one man is going to be overwhelmed.

While too heavy a chassis is a waste too light a one reduces accuracy or rate of fire. Recoil spades help but too much gun for the chassis means a lot of bounce between firing and the gunner has to re-aim the gun more often, or at least check the aim. Some towed guns suffered from this.

[davebender]

Rate of fire is nice but having enough HE filler in the shell to defeat field fortifications such as concertina wire is more important for indirect fire artillery. That lesson should have been learned during WWI. I'd rather be supported by 120mm mortars then 25 pounder field guns. Not as accurate and range is shorter but at least they have enough punch to get the job done.

[Shortround6]

Problem being that if your opponent has 25pdr field guns and a competent spotting group you won't have your 120mm mortars very long.

If you are depending on 120mm mortars to defeat field fortifications then your divisional and corp artillery are not doing their job.

How much effort did the Germans put into lengthening the range of their 105 howitzer from 10,675meters to 12,325 meters?

[tomo pauk]

The mechanized chassis costs a lot more then a 105mm howtizer. If Britain cannot afford to purchase light howitzers then how are they supposed to purchase SP artillery of any type?

Price examples.
16,400 RM. 10.5cm leFH18 howitzer.
22,000 RM. Sd.Kfz.11 towing tractor. Normal tow vehicle for a 10.5cm howitzer.
about 50,000 RM. Panzer II. The smallest possible chassis that can carry a 10.5cm howitzer.

In British case, they will initially use the guns that are already produced, or are being produced; the artillery branch will use a chassis priced between the Bren carrier and Pz-II (while it would be produced less 'real' light tanks), while the tank branch will not buy historical CS tanks, but the SP assault guns (main task providing HE support for 2pdr armed tanks & accompanying infantry).

For the 25pdr the firing rates were

Rates of fire---------Gunfire------Intense------Rapid------Normal--------Slow--------Very slow

Rounds/Minute------6 to 8---------5------------4----------3------------2--------------1

I haven't found the firing rate/s for the 18pdr yet but I would be very surprised if it was under 12 rounds a minute for it's max rate of fire and may have been as high as 15-20rpm with prepared (fused) ammunition. Shell was crimped to cartridge case so one piece loading with no charge adjustment.

A US 105 howitzer was supposed to do 8rpm for the first 1/2 minute, 4 rpm for 4 minutes, 3 rpm for 10 minutes and 100 rounds an hour. If the crew has time to prepare ammo and lay it out (zone charges adjusted and shells fused) then having a single loader ammo handler might not be too bad, depending on far from the gun breech the rounds are after the first 10 or so. That is assuming they want 25-30 fused shells laying about. If fuses have to be fitted and zone charges adjusted while firing one man is going to be overwhelmed.

Many thanks for the fire rates.
The LT-based SP vehicle should have 2 loaders, commander, aimer and driver (as it was the case for the German conversion). Once in the firing spot, the driver can assist the loaders.
The A9 based vehicle will fire as fast/as slow as the StuG-III with long 7,5cm.

While too heavy a chassis is a waste too light a one reduces accuracy or rate of fire. Recoil spades help but too much gun for the chassis means a lot of bounce between firing and the gunner has to re-aim the gun more often, or at least check the aim. Some towed guns suffered from this.

Comparing the British conversion with German, the shell weight is some 45-50% less in the British example, MV being about the same, so the recoil is about a half of what was the case for German conversion.

Once more, I agree that too light/small a vehicle can hamper the performance, but once more I repeat that British*, in this thread, are still learning about the finesses of the SP artillery. Some 3 years earlier than historically

*didn't even started with others yet

[Shortround6]

Tomo, the German conversions of the MK VI tank used a WW I left over howitzer, not the standard howitzer. Barrel was about 300mm shorter, top velocity with the zone 5 charge was 395m/s. max range 9225 meters. 4 degrees of traverse (?) 2 to each side of centerline.

[tomo pauk]

Thanks for the correction; I knew that the 10,5cm lefh 16 was in question, but assumed that MV values are similar.
So, if I'm calculating it correctly, the 10,5cm shell has the momentum equal to 5846 kgm/s vs 4132 for the 18pdr, or, the 18pdr has a recoil of some 72% of the lefh 16?

[davebender]

How much effort did the Germans put into lengthening the range of their 105 howitzer from 10,675meters to 12,325 meters?

None.

The 10.5 cm leFH 18/40 change was intended to lower production cost. A bit more range and higher rate of fire was just a bonus.

[Shortround6]

Thanks for the correction; I knew that the 10,5cm lefh 16 was in question, but assumed that MV values are similar.
So, if I'm calculating it correctly, the 10,5cm shell has the momentum equal to 5846 kgm/s vs 4132 for the 18pdr, or, the 18pdr has a recoil of some 72% of the lefh 16?

Could be, 70-80% should be in the area ( weight of propellant times escape velocity of the gasses). The German conversion was done by/for a second line unit that probably couldn't even get enough draft horses.