Q. on Preists and Sextons

[JonS]

When the British put the 25-pr in the Sexton, they lost about 2,400yds of range (from 13,400yds down to 11,000yds), due to the limits of elevation within the vehicle.

Range of the towed US 105mm M1 How was - from what I can figure - about 11,500m, and it had a max elevation of 65°. When this How was put into the M7 Priest the max elevation was restricted to 35°. What I cannot find is the range of the 105mm How when mounted in the M7. Since max elevation in the veh is considerably below 45° (theoretical optimum elevation for max range), I'd expect that max acheivable range is also considerably less than the towed version.

Does anyone have reliable info on the range of the US 105mm How, in both its towed and SP incarnations?

Thanks

Jon

[Kingfish]

So, I hear you're giving out cookies.

Hmmmmm?

[JonS]

Heh. Depends on your answer

[stoat]

The 105mm howitzer M2 was the standard 105mm howiter during WWII. From 1942 on, the electric Warner brakes were removed from the carriage, and the M2A1 was born. This was the version that was mounted on the M7 and M7B1.

Maximum elevation for howiter on carriage: 64 degrees, 15 minutes

Maximum range: 12,205 yards (sorry, not in the mood for conversions)

Maximum elevation for M7 and M7B1: 35 degrees

The max range for these vehicles is still listed as 12,200 yards, though as you have pointed out, the physics of it simply don't compute. On some occasions, the Priests would be driven onto fashioned ramps to provide a greater angle of elevation, perhaps more akin to the later M37 that had a maximum elevation of 45 degrees while mounting the same howitzer.

[Kingfish]

Originally posted by stoat:

Maximum range: 12,205 yards (sorry, not in the mood for conversions)

I, on the otherhand, am rock hard and ready for action:

12,205 yards=

11160.25 meters

36615 feet

439380 inches

55.47727 furlong(s?)

6.934659 miles

6.026072 nautical miles

3.616806e-013 Parsec(s?)

1.179668e-012 Light years

[stoat]

Originally posted by Kingfish:

I, on the otherhand, am rock hard and ready for action:

All that, and you didn't convert into rods?

[JasonC]

Theoretically you lose about 6% of the maximum range if you are restricted to 35 degrees as a max angle, compared to 45. That is ignoring air resistence, but should be close enough. That implies a range reduction of only about 700 meters, maximum.

The real reason they never fire at full maximum (for any large number of shots at least) is doing so requires the maximum charge 7 (or "super" for 25 pdr), which will dramatically increase barrel wear, compared to firing charge 5 or so. Unless there is an absolute need, that simply isn't worth it. You are better off displacing slightly forward and using a lesser charge. Counterbattery is not a great danger against an SP unit anyway - the guns are much better protected than towed and displacement much easier etc.

In Korea, they modified the Priest to allow a full plus 65 degree angle of fire, as the M7B2. The reason wasn't concern about range but final angle of descent. Large hills simply create too much dead ground if you are restricted to the lower angle of fire. With the upper quadrant available, you can reach the same range by the longer hang time, steep trajectory. Normally that would be avoided because more time in the air is going to increase wind drift and so reduce the accuracy. But if it is the only way to hit a reverse slope, that is well worth it.

[JonS]

Hi Guys,

thanks for the info.

Jason

6% seems like an unreasonably small reduction, given that you're losing a bit over 20% of the potential elevation - is this an 80/20 or helical thing (range is relatively insensitive to the last 20% of elevation)? It still seems odd though - putting the 25-pr into the RAM chassis to produce the Sexton reduced that guns max elevation from 45° to also 35°, but in that case the max range dropped from 13,400yds to 11,000yds - or nearly 18%.

Funnily enough, I get your other points. I'm playing around with the OoB file for HPS' PzC:N44, and am trying to get valid distinctions between towed and SP guns (note to self: check the 105mm lFH/Wespe and 150mm sFH/Hummel). I've addressed set up times, and wanted to distinguish between achievable ranges too. Given that the game uses 1km hexes great precision isn't required (i.e. 9.76km is as good as 9.81km for this this purpose), but a difference of ~20% in range is certainly significant.

Cheers

Jon

[ May 26, 2007, 02:03 PM: Message edited by: JonS ]

[JasonC]

As you lower the angle from 45, you lose initial vertical velocity, and with it time. But you also increase the horizontal velocity, and thus the distance covered per unit time. The achieved range is a parabolic function of the angle, and you are near its maximum.

Remember that right at 45, the derivative of the achieved range with respect to the angle is zero, so very slight differences in the angle, near 45, make no difference in the range, small ones make a small difference, etc.

[JasonC]

As for the range differences between towed 25 pdr and Sexton 25 pdr, I have seen range cards for the towed that include charge Super, beyond charge 3. I have never seen a range card for the Sexton that shows a Super line.

[JonS]

Originally posted by JasonC:

I have never seen a range card for the Sexton that shows a Super line.

Now you have.

[JasonC]

That is one I have seen, but apparently I misinterpreted it. I read the bottom panel as being for the SP version, now I see it is the jungle variant ("light" carriage").

[JonS]

Yeah, the bottom panel is for the Baby 25-pr. But just above that is this:

Q.F. 25-pr Gun Mk 2 on Carriage 25-pr Self Propelled Sexton

Ordnance: No differences from Gun Mk 2

Elevation: Maximum elevation of 35° reduced maximum range with charge Super to 11,000 yds on level ground

Granted, it isn't a full range card.