What if the French Navy used its explosive shells in 1798?

[Bad@logic]

As related in Science and Polity in France: The Revolutionary and Napoleonic Years, the French had a multi-year program for developing incendiary and explosive shells, principally intended for the navy. Extensive tests with the explosive shells in 1798 at Meudon, using 1794/95 produced ordinance (found to still be reliable and to not have degraded), fired by land batteries against land targets which represented ships of the line, proved to be highly effective, although with the provisos that accuracy was dismal since it was the first time that gunners were firing something other than round shot, so the shells had a tendency to go high. Previous 1794 tests had been carried out by the French ship La Montagne, and had again been quite effective for explosive shells (in both cases, incendiary shells did not work as well): in response some 300,000 shells had been ordered to be manufactured, joining around 5,000 previously constructed prior to 1795. In a battle in 1795, a French frigate was ordered to use its explosive shells by the command of Etienne-François Le Tourneur, and put 3 English ships out of commission at Cape Noli. However, the French Navy displayed little interest in the idea - advocates of the new ordnance claiming it was due to conservatism and fear of obsolescence of its ships of the line, although I suspect it came much more likely from the fear of being blown up by its own shells, an entirely reasonable and justified fear.

The Meudon Commission recommended that 10 explosive shells and 5 incendiary shells be provided for each cannon of 36, 24, and 18 pounds, with appropriate instruction on their use and safety procedures. The book does not mention whether this was ever acted upon. But what if it was? What if the French Navy was equipped with explosive shells, and acting upon this perceived gain in combat effectiveness, was ordered to go ahead with its planned invasion of England and engage the Royal Navy in a pitched battle?

What would be the effect of the shells on the British?
How many French ships would succeed in blowing themselves up with dangerous ordinance on-board?
If the French navy did succeed in winning a temporary tactical and operational victory over the Royal Navy, could it go on to invade the UK?

 

[RodentRevolution]

I am going to start my response by quoting Dahlgren

The prime purpose of the shell, as already stated, is to lodge in the object, such as the side or contiguous material of the ship...

From Shells and Shell-Guns by J.A. Dahlgren page 212

The result is a much larger cloud of splinters which kill the crew or even with a large enough round serious damage to structure of the ship that might impact its viability as a sea-going vessel. However there is an art to this and a lot of shells will fail to lodge and inevitably due to mechanical issues with the fuses some of those will fail to detonate. However explosive shells if properly handled would go someway to compensating for deficiencies in the French rate of fire compared with more highly trained British gun crews.

It might not be a battle winner by itself but it would go someway to reduce the obviously lopsided casualty results that tended to be the case when French ships went up against British ones. Now some ships would go bang by themselves but overall I would expect a net French gain. However the point is the British by 1795 were enjoying an exceptional firepower advantage on a per ship basis than the French and typically had better handling to boot so explosive shells would only go someway to compensating for this. The big issue though is that ten rounds per gun is probably nowhere near enough for most actions and the incendiaries while theoretically nasty could be handled by existing fire fighting techniques.

It should be noted that Paixhans and Dahlgren were firing shells of some 50 and 60lbs while the shell from a 36 pounder gun would be less than half that at around 24lbs.

 

[Mikestone8]

The obvious response would be red hot cannon balls. Just one landing among those shells and the ship would be history.

 

[Bad@logic]

The obvious response would be red hot cannon balls. Just one landing among those shells and the ship would be history.

I'm doubtful this can be applied to normal circumstances. Firstly, most ships did not carry the tools to provide for heated shot. There was an experimental French frigate class which had a forge onboard for heated shot, but well, they realized that having a forge for heated shot on a wooden ship was a... questionable idea. In fact, the idea relates to me as being similar to the French explosive shell project: sure, it is a leap in lethality, but it also will have a painful tendency to blow up your own ships. Shore installations could fire heated shot of course, but that's no real difference.

The other thing I question is whether the ships would be more vulnerable to enemy fire because of having the shells onboard. Ships are already floating powder magazines, and a heated shell hitting their powder is a deadly threat. I don't see why having the explosive shells are particularly more at risk to enemy fire than the powder. I do see very well why they are a deadly threat to one's own ship, since it is very easy to not align the fuzes properly or to mishandle them, but enemy fire I don't think would pose a greater threat than against a regularly-armed vessel.

 

[SwampTiger]

The reliability of the shells will be a substantial determinant of their effectiveness. If the French use shells of fairly high (75% or more) reliability, the British will be surprised. The accuracy of the gunners will be the major determinant. French gunners typically aimed high, which some attribute to attempting to damage rigging. More likely it was lack of experience. Failure to hit hulls will greatly diminish the effect of shells. Since shells are lighter than shot, the gunners must now adjust for the change in trajectory. Without more practice by the French naval gunners, I do not foresee a huge impact in the first two or three engagements.

The occasional accident is the expected. Training would reduce accidents. However, the French hadn't trained their gunners and crew sufficiently up to then.

Should the French Navy destroy one British fleet, it will have to face a second fleet before landing troops on England. How many sixes can they roll consecutively? Once troops are landed, you need to supply and reinforce your expedition. Thus, you will face additional British fleets. The number of explosive and incendiary shells is insufficient. The wooden ships of the time could be destroyed by shell. However, I doubt a French crew of the time could accurately place enough shells to incapacitate a British ship before running out.

This isn't to say a good French captain would not be able to take advantage of the new shells and sink a few unsuspecting British ships, only that the fleets would have insufficient training in the proper use of shells. Note, the British reaction will be to design shells of their own, which is their reaction in OTL.

The Battle of the Nile may have interesting changes though.