Lutzow vs. US heavy cruiser

[lwd]

I love the British Town class, they probably dont have to much wrong with them (for CL's)
Give me 12 X 6inch over 6 X 8 inch anyday (sorry but I just dont like York/Exeter)

The only thing is the shorter reach. At the River Plate it was Exeter that was able to put AGS under fire at maximum range, and land two hits before being clobbered. Can't see 12 x 6 inch as being able to do damage to AGS that early in the action....

Part of this is the round as much as the caliber is it not though?
http://www.navweaps.com/Weapons/WNBR_6-50_mk23.htm
Shows no AP round just 112lb CPBC and HE rounds for the British weapon. On the otherhand
http://www.navweaps.com/Weapons/WNUS_6-47_mk16.htm
Shows the US haveing a 130lb AP round. A similar round for the British weapon might allow for more damaging hits both at longer and shorter ranges.

[tommy303]

On the other hand, the USN 6in AP had slightly less than 2-lbs of ammonium picrate for a filler as opposed to the RN 6-in CPBC having+ nearly twice the weight of Shellite which pound for pound is about 27% more powerful than ammonium picrate. It appears that the British preferred a shell with greater explosive effect at the target, even though it meant a reduction in armour piercing capability, where as the USN philosophy was the opposite. It is difficult to say which was the best philosophy, but most navies appear to have preferred to use a CP or SAP type piercing shell for their 6-in instead of a full APC. It is best to remember though, that light cruisers generally were not intended to take on heavily armoured targets where AP would have been appropriate.

[Bgile]

On the other hand, the USN 6in AP had slightly less than 2-lbs of ammonium picrate for a filler as opposed to the RN 6-in CPBC having+ nearly twice the weight of Shellite which pound for pound is about 27% more powerful than ammonium picrate. It appears that the British preferred a shell with greater explosive effect at the target, even though it meant a reduction in armour piercing capability, where as the USN philosophy was the opposite. It is difficult to say which was the best philosophy, but most navies appear to have preferred to use a CP or SAP type piercing shell for their 6-in instead of a full APC. It is best to remember though, that light cruisers generally were not intended to take on heavily armoured targets where AP would have been appropriate.

Since the British cruisers accomplished their mission, I don't suppose we can say that their ammunition was unable to do the job. However, I think the original question was about ONE cruiser vs AGS and in that case 8" AP might have been superior, but I think it would be a tough call even then and the US ship would have to be lucky in where it's hits occurred.

[lwd]

On the other hand, the USN 6in AP had slightly less than 2-lbs of ammonium picrate for a filler as opposed to the RN 6-in CPBC having+ nearly twice the weight of Shellite which pound for pound is about 27% more powerful than ammonium picrate. It appears that the British preferred a shell with greater explosive effect at the target, even though it meant a reduction in armour piercing capability, where as the USN philosophy was the opposite. It is difficult to say which was the best philosophy, but most navies appear to have preferred to use a CP or SAP type piercing shell for their 6-in instead of a full APC. It is best to remember though, that light cruisers generally were not intended to take on heavily armoured targets where AP would have been appropriate.

Well the US also had a HE round for their 6" guns. But they clearly invisioned them as fighting against other cruisers.

[lwd]

...I think the original question was about ONE cruiser vs AGS and in that case 8" AP might have been superior, but I think it would be a tough call even then and the US ship would have to be lucky in where it's hits occurred.

That's true to some extent no matter what the guns but 12 or 15 guns firing at a higher rate do increase the chance of "lucky" hits considerably.

[RF]

Since the British cruisers accomplished their mission, I don't suppose we can say that their ammunition was unable to do the job. However, I think the original question was about ONE cruiser vs AGS and in that case 8" AP might have been superior, but I think it would be a tough call even then and the US ship would have to be lucky in where it's hits occurred.

Rasenack, in his book on AGS, was very clear that the 8 inch guns of Exeter posed a much more serious threat than the 6 inch of Ajax and Achilles, because of the penetration capability and the thin armour of AGS.
At the very start of the River Plate action, Rasenack considered that an 8 inch shell could and very nearly did penetrate into the AGS engine rooms and almost immobilise the ship.....

Bgile is right in saying that the light cruisers were able to finish the job, but that was largely courtesy of the mistakes of Langsdorf. Had Langsdorf kept the range open and not rushed in, there would have been a different outcome, probably far more favourable to the Germans.

When I originally initiated this thread, I chose a US heavy cruiser as opposed to a British one because I thought that the US heavy cruiser would be a tougher prospect overall for a panzerschiff to fight in an all out one on one action.

[tommy303]

Curiously, a British survey team examining the wreck came to the conclusion that the RN shells were not performing up to the standard expected of it. A US cruiser early in the war might have been in a similar if not worse situation as there were frequent failures in the Mk 11 BD fuze with which the majority of 6-in and 8-in piercing shells were equipped until 1942 when it was replaced by the MK21. The Mk11 was an attempt to produce a smart fuze which could sense when it had penetrated armour before initiation the explosive train. It worked well enough under controlled conditions, but when mass produced and employed in combat, did not live up to its designer's hopes and the dud rate was phenominally high. For one, the fuze had to be manufactured to extremely tight tolerances, not always achieved in mass production, and secondly, it had not been appreciated that the ammonia fumes from Explosive D tended to corrode the internal workings of the fuze during long periods of storage and thus making them more likely to jam. This latter problem also plagued the Mk21 until about 1943 when it was found that sealing the fuze with bakelite solved the corrosion problem.

[Bgile]

Curiously, a British survey team examining the wreck came to the conclusion that the RN shells were not performing up to the standard expected of it. A US cruiser early in the war might have been in a similar if not worse situation as there were frequent failures in the Mk 11 BD fuze with which the majority of 6-in and 8-in piercing shells were equipped until 1942 when it was replaced by the MK21. The Mk11 was an attempt to produce a smart fuze which could sense when it had penetrated armour before initiation the explosive train. It worked well enough under controlled conditions, but when mass produced and employed in combat, did not live up to its designer's hopes and the dud rate was phenominally high. For one, the fuze had to be manufactured to extremely tight tolerances, not always achieved in mass production, and secondly, it had not been appreciated that the ammonia fumes from Explosive D tended to corrode the internal workings of the fuze during long periods of storage and thus making them more likely to jam. This latter problem also plagued the Mk21 until about 1943 when it was found that sealing the fuze with bakelite solved the corrosion problem.

So Washington must have sunk Kirishima with mostly dud shells?

[dunmunro]

I know that USN 5" AA fuzes had a very high dud rate in 1942.

[tommy303]

I believe Washington's 16-in had the Mk21 BDF. In some early engagements it appears to have performed reasonably well with no higher dud rates than experienced in other navies, while in others its dud rate was very high. In some cases this might be attributed to high oblique impacts. The fuze itself was highly complex with several bore safety features and detents to lock the various safeties in armed position so that a fuze was less likely to disarm itself as it was subjected to the stresses of penetration and subsequent travel within the target until the delay burned through and set the thing off. Sufficient corrosion due to the Explosive D fumes could have caused the striker pellet to jam at very oblique impacts as may have been the case at Casablanca when USS Massachusetts engaged the Jean Bart, or to have caused a failure in the detents to keep the safety interlocks in the armed position. In the night action where Washington defeated Kirishima, the ranges were less and presumably the impact angles may have been less on the average than was the case with Jean Bart. At closer to normal impact, the striker was less likely to jam due to corrosion than at more oblique angles; there may also have been less stresses at the lower angles of impact on the detents and safety interlocks, so that if corrosion had prevented a safety from being locked in armed position, lesser stress due to less radical changes of direction during penetration or post penetration yawing may have permitted normal function.

Ducan,

yes, again failure rate of AA common may well have been due to the use of Explosive D. Following Casablanca, the problem was diagnosed and steps were taken to seal the fuzes from fumes.

[RF]

A US cruiser early in the war might have been in a similar if not worse situation as there were frequent failures in the Mk 11 BD fuze with which the majority of 6-in and 8-in piercing shells were equipped until 1942 when it was replaced by the MK21.

If Lutzow did engage a US cruiser with the mark 21 in say late 1942 in either North Atlantic or in the Arctic convoy area, on a one to one basis, would you favour Lutzow? or would the balance be tipped?

[tommy303]

If Lutzow did engage a US cruiser with the mark 21 in say late 1942 in either North Atlantic or in the Arctic convoy area, on a one to one basis, would you favour Lutzow? or would the balance be tipped?

That's quite a difficult question to answer. The problems with the Mk21 were not solved until the introduction of the sealed Mk21 Mod 1 in mid 1943, so in any action before then, one would be taking one's chances. If your store of shells and fuzes had only recently been delivered, you might not experience a higher than normal dud rate, as the question here is shelf life. If the shells and fuzes had been together in the magazines for five or six months (in the USN shells were fuzed at the muntions depot before being sent out to a ship), corrosion would have set in greatly increasing the tendency of the shell to be a dud. The other problem with this fuze was it did not have a graze action feature like the German C/38 BDZ, which meant that at very oblique impacts, such as the shell which glanced off of Jean Bart's barbette capping plate, the fuze would be unlikely to function at all. On the other hand, not having a graze action feature did make the fuze more robust and less subject to fuze damage at low angle/high velocity impacts than fuzes with graze action. It was something of a trade off depending on which was more important, reliable functioning at low angle impacts or reliable functioning at oblique impacts.

The Mk 21 Mod 1 had all external joints sealed with a coating of Bakelite varnish over lacquer.

Given that any engagement taking place in 1942 would essentially see the US ship possibly entering deadly combat seriously handicapped by defective fuzes (sort of like a prize fighter entering the ring with a broken arm), I would have to favor the Luetzow. At closer ranges, the Mk 21 Mod 0 might perform well enough, as was the case in the Washington vs Kirishima, but at the same time this would subject the US ship to accurate 28cm shell fire and possibly torpedo attack--a lethal combination.

[Dave Saxton]

So Washington must have sunk Kirishima with mostly dud shells?

I'm sure a percentage of them were duds. Consider at a range of 8,000 yards the impact velocity would be about 644 M/s, and any duds would probably pass completely through the Kirishima and hole the starboard side below the water line, prior to Kirishima altering course toward the north. Even shells that functioned properly would likely travel~ 22 meters before exploding after penetrating the port side. Kirishima's max beam was only 29 meters.

[Bgile]

There is also the fact that a "dud" can do a lot of damage. It doesn't mean the shell somehow vanishes. There will still be lots of secondary frag effects and anything in it's path will be destroyed.

[Dave Saxton]

I have mixed up my rights and lefts in the above post. For the most part Kirishima was presenting her starboard side to Washington, but both right and left sides were presented at different times.