First test with Fireflies vs King Tiger

[John Kettler]

Fascinating stuff! I'd like to contribute a bit to the discussion. The British 15 inch/L42 naval gun was originally planned to have a higher MV than subsequently was the case, but firing trials discovered a critical problem. The problem was barrel whip, and was discussed in the book BRITISH BATTLESHIPs (was shown this information by some Hughes naval grogs in the late 1970s, my department head, John Green and our weaponeer, Bob Martin) cited here under sources.

http://www.navweaps.com/Weapons/WNBR_15-42_mk1.htm

Further, note g) at the above indicates that the planned new, hotter, propellant and larger charge created a spread of MVs greater than the current one, further degrading gunnery accuracy. As I recall, slowing the MV down by a few hundred FPS and sticking to more consistent propellant eliminated the problem.

So, it does NOT ineluctably follow that higher velocity is always a better solution in gun design. Like everything else, it comes with a price. Be it ROF sacrificed because longer, more powerful shells are heavier than short American 75mm shells and take longer to load, shorter service life because of bore and other wear, redesign and weight penalties to deal with strong recoil forces (trials of a 105mm L7A1 in an Israeli Sherman shattered the turret, forcing the use of the softer French 105mm; the British went through all kinds of grief to field the Firefly, including turning the gun on its side and adding hundreds of pounds of counterweight to the rear of the turret to offset that long deadly gun and its attendant moments).

NOTHING is free in engineering. EVERYTHING is a tradeoff. The Firefly mounts a tremendously powerful gun, but that gun is a) scarce (one per troop of five tanks at Normandy) and mounted on a Ronson. Bluntly put, the Firefly is a fully turreted Allied eggshell with a hammer, as so beautifully put by JasonC regarding a bunch of thinly protected, heavily armed German AFVs.

The APDS issue is yet another tradeoff--penetration performance superior to HVAP, but at a cost of far greater design and manufacturing complexity, not to mention the accuracy problems and terminal effectiveness problems given a suboptimal skewed impact, both resulting from the teething woes of discarding sabot technology.

It would be most interesting to know what the opportunity cost was to the British of fielding the Firefly, especially in the dispersed manner they did. Had it been the Russians with such a weapon, I feel confident in asserting they would've wound up massed in specialist formations, which would've greatly simplified logistics, maintenance and combat repairs. Tanks are hard enough to keep working, let alone two significantly different types in one platoon!

Regards,

John Kettler

[Vanir Ausf B]

Sabot rounds also had reduced after-armor effects due to the smaller caliber of the penetrator..

[dieseltaylor]

I think the British got it right by mixing them up as both had strengths to play to. It also undoubtedy kept the German tankers nervous as if you saw some vanilla Shermans there was good odds that lurking further back was a Firefly or two.

I imagined the speed of the shell, if it penetrated, would bring attendant lumps and shards of metal which maybe not as satisfying but at least it got through.

[John Kettler]

dieseltaylor,

Especially considering that deceptive paint jobs were used to hide the Firefly and prevent the Germans from preferentially targeting it! Pics of several such paint jobs below.

http://beute.narod.ru/Beutepanzer/us/M4_sherman/uk/firefly-1.htm

All,

for anyone who took the time to wade through the long, groggy 15 inch gun article, here's the definition of crh.

http://www.navweaps.com/index_tech/tech-094.htm

Regards,

John Kettler

[Hister]

Erm, that firefly was captured by Germans - no deceptive paint job there.

[bobo]

Erm, that firefly was captured by Germans - no deceptive paint job there.

I think he knows that and was joking? 50-50 on that comment.

[John Kettler]

Hister and bobo,

Since I was looking for specific pictures illustrating one particular point, I was totally focused on that, to the point where I failed to notice that all of the tanks were captured. Wasn't reading captions, either. Oops! that said, the pics do illustrate one of the techniques for hiding the telltale 17 pounder barrel.

Here's one that wasn't captured and shows both the wavy pattern and an attempt to trick the eye into seeing a short gun barrel. Judging from the tans on the crew, I'd say this pic was taken in Italy, where the Germans enjoyed excellent observation. This most definitely is a deceptive paint scheme.

http://www.treefrogtreasures.com/forum/attachment.php?attachmentid=85766&d=1328699710

Regards,

John Kettler

[Streety]

Yes, the wavy front underside camouflage to the Firefly's barrel was to hide it's length and so make it less distinguishable from the other British Shermans.

The reason for their spread-out distribution among existing tank units (rather than massed into tank-killer formations) was partly that initially they didn't have enough to go round (because it was originally only meant to be a stop-gap due to problems delaying the newer Challengers and Cromwells entering service). And partly because in planning for Normandy the Allies had mistakenly believed that the new Panther tank would be much rarer than was to be the case, and thought they would similarly be spread out piece-meal among existing Panzer IV units rather than being a replacement for such units.

[bobo]

Hister and bobo,

Since I was looking for specific pictures illustrating one particular point, I was totally focused on that, to the point where I failed to notice that all of the tanks were captured. Wasn't reading captions, either. Oops! that said, the pics do illustrate one of the techniques for hiding the telltale 17 pounder barrel.

Here's one that wasn't captured and shows both the

John Kettler

I can totally see that. I didn't notice the barrel paint scheme until I looked again. It seems like something should have been done with the extended rear end of the Firefly turret. That certainly stands out.

Bobo