U.S. Smoke Shell Effectiveness

[rexford]

Some time ago a generous fellow e-mailed me three pages from a U.S. handbook that included some interesting info about American smoke rounds. The following info answers some of the questions I have been raising on various sites (source of text and drawings has been lost, and would appreciate reference if fellow who sent material reads this):

HC SMOKE SHELLS (Base Emission)

Shell is used by bouncing it off the ground about 100 to 300 yards away from intended aim point (ricochet fire), useful range is 850 to 1600 yards.

Paraphrasing the text:

Single tank use of smoke is not going to be effective, it takes a section or entire platoon to smoke a small area. "The section or platoon fires three or four rounds per gun in about one and one-half minutes to screen a suspected area. It takes one to two minutes to build a good screen."

The text mentions that tanks generally carry a small load of smoke rounds, and smoke application should be left to tank battalion assault guns and mortars

Based on the above, smoke is not going to help much against Panthers at 500m unless one can land a shell on the turret front that stays put. Firing smoke rounds at a Panther or Tiger for one to two minutes would certainly leave one open to quite a few rounds in return before the smoke screen really reduced Sherman vulnerability.

The reason for the ricochet range to target, and 850-1600 yards useful range, is not clear.

Does the smoke effect take place after the round comes to a stop?

WHITE PHOSPHORUS SMOKE SHELL

Paraphrasing text:

Less screening effect than HC shell due to pillar effect, but "produces an immediate screen on impact, causes wounds and starts fires".

White phosphorus would seem to be effective for screening at any range, and might be more effective at close range due to less random scatter along the line of fire.

The above suggests that a white phosphorus round fired at the ground in front of a Tiger II might still not block the view needed for a return shot if the pillar is not precisely placed or a gust comes along.

The drawings show white phosphorus rounds being used to drive German soldiers out of trenches, pillboxes, bunkers, anti-tank gun emplacements and other defensive positions.

GENERAL NOTES ON SMOKE ROUND USE

"Smoke is most effective at dawn or dusk on open terrain, in overcast weather and in steady low velocity winds"

"A cross wind of from three to six miles per hous is ideal. When the wind velocity is high (15 mph), the rate of fire must be faster than in a slow wind. A wind blowing toward the enemy is desirable during an attack since the smoke blows over the hostile rear areas, blinding the supporting weapons."

The above suggests that firing smoke on a bright sunny day will be less effective than dark day use.

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From a wargame viewpoint, Advanced Squad Leader treated smoke rounds as line of sight impediments that reduced hit probability but did not eliminate the chance, and effective smoke application was far from a certainty.

[lcm1947]

Some very useful and interesting info. Thanks JasonC. It sounds like tank use of smoke wasn't all that effective? Wonder what they had in mind when they stocked it in tanks? I agree about smoke taking too long to to avoid your tank from being killed by another tank. Happens to me all the time in the game and sounds like this was programmed correctly but AI sure gets it to be useful. I'd sure rather use a regular round trying to knock the other tank out then trying to use smoke to block it.

[tar]

Well, the description of the HC shell usage certainly suggests that it was used to screen other units from the enemy rather than the tanks themselves. The time to deploy the screen seems to have been around 3 minutes or so: 1 1/2 to fire the rounds and then another 2 minutes or so until the screen became effective.

WP shells have more of the character of offensive weapons. Certainly getting hit with WP fragments results in a nasty, burning wound and water will not extinguish the WP.

[lcm1947]

Oh, oh. In my above post I stated thanks to JasonC when it should have said rexford. Damn I hate it when I don't proof read my posts.

[John D Salt]

Originally posted by rexford:

Some time ago a generous fellow e-mailed me three pages from a U.S. handbook that included some interesting info about American smoke rounds. [snips]

Based on the above, smoke is not going to help much against Panthers at 500m unless one can land a shell on the turret front that stays put.

Possibly so, but I would have thought that a more natural response from a Sherman TC would be to lay smoke using the 2-in smoke mortar, and use the 75 to make the Panther crew's ears ring with an HE round. Hunnicutt's "Sherman" lists the smoke mortar for all Sherman gun tanks it gives data sheets for apart from early production M4A1s and M4A4s.

Originally posted by rexford:

[snips]

The reason for the ricochet range to target, and 850-1600 yards useful range, is not clear.

Does the smoke effect take place after the round comes to a stop?

I would hazard a guess that emission starts when the round first strikes the ground, and the reason for using ricochet fire is to try to speed the development of the screen.

All the best,

John.