lorrin

Thanks to all who responded for all the drawings and stuff. Regarding the above quote, that material underlying the curved mantlet appears to be an extension of the turret front armor which curves upward. Do you think so? Anyway, it's a very good observation. If the underlying material is an extension of the turret front armor (110mm), it would add a rather large amount to the resistance of the lower mantlet area and make it almost inpenetratable. What do all of you think? Lorrin

I ran Jeff's example on a ballistic computer program using his data for the rifle round and filled in the missing pieces with data from the U.S. 0.30 caliber AP bullet: bullet diameter=0.308"=7.82mm bullet weight=146 grains=0.009432 kg T1 projectile with 0.55 form factor 2775 fps muzzle velocity 1925 fps at 400 yards (U.S. 0.3 caliber AP) 1725 fps at 500 yards (U.S. 0.3 caliber AP) Elevation angle for 500 yard shot at target with same height as gun = 0.246 degrees CASE 1 PRONE FIRER, 1' above ground 0.2387 degrees from gun to 6' tall target at 400 yards 0.4847 degree gun elevation for 500 yard shot Bullet passes 400 yard target range at 2.238m or 7.341' elevation, overflies aim point by 88.09" - 72"=16.09" CASE 2 STANDING FIRER, 5.5' above ground 0.02387 degrees from gun to 6' tall target at 400 yards 0.2699 degree gun elevation for 500 yard shot Bullet passes 400 yard target range at 2.234m or 7.328' elevation, overflies aim point by 87.93" - 72"=15.93" CONCLUSION If the prone and standing firers both aim at the same point and elevate their guns for a 500 yard shot the rounds from both guns will overfly the target aim point at 400 yards by about the same amount.

Jeff, Yesterday was a bit hurried and I really should look at the example you provided for a rifle shooter at different heights. You made the effort to look at the topic under discussion and you deserve a fair review of your material. If you will post the flight times of the bullet to 400 and 500 yards, and the elevation range to fire at a 500 yard target that is even with the gun barrel, the exact situation will be looked at in detail. During the interim I used some stats for the U.S. 0.30 caliber machine gun bullet: 2775 fps muzzle velocity 1925 fps at 400 yards 1725 fps at 500 yards Flight times are about 0.511 seconds to 400 yards and 0.667 seconds to 500 yards. The elevation for a 500 yard shot at a target level with the gun is about 0.274 degrees using the simple model that has been applied in this thread. PRONE FIRER Assume gun barrel is 12" above ground. Angle from barrel to target aim point is 0.238 degrees. Firer elevates gun to 0.238 + 0.274 degrees, for 0.512 degrees. Height of trajectory at 400 yards is: 1' + 1200' x tangent (0.512 degrees) - 0.5 x 32.2 x 0.511squared or 7.52' (90.23 inches), for a miss by 18.23 inches high. STANDING FIRER Gun barrel at 66 inches or 5.5'. Angle from firer to target aim point is 0.0239 degrees. Add elevation for 500 yard shot to obtain final angle of 0.298 degrees. Elevation of round at 400 yards is: 5.5' + 1200' x tangent(0.298 degrees) - 0.5 x 32.2 x 0.511squared or 7.54', which equals 90.45 inches. Bullet flies over aim point by 18.45 inches. About the same as prone firer situation. Based on the above analysis, it appears that standing and prone firers miss the aim point by about the same amount for the same aim point and range estimate. Lorrin

Thanks, good info.

Through the years I've seen drawings which illustrated the tapering thickness of the Panther mantlet, where the thickness varied from 100mm at the center to about 75mm at the upper and lower edges. To complete some studies for another thread it would be appreciated if someone would be so kind as to post up a section drawing of the mantlet that shows the thickness changes. My stuff is in storage (as usual), as we've just moved, and it's way in the back of the shed. The IS-2 mantlet varied from 110mm to 75mm and one Russian book indicated that the mantlet thickness was 75mm. Thank you. Lorrin

Two of the three examples I provided looked at the effect of barrel height on shots where there were range estimation errors, and barrel height did not influence the result. Your additional caveat has already been addressed.

Now let's look at things from the Allied perpective for a change, and we'll stick with tank guns since that is what is under study. Also using the same simple trigonometric model. Example Details =============== A 17 pdr armed Firefly is getting ready to fire off an APCBC round at a PzKpfw IVH that is 600m away but the Firefly crew thinks it is 800m distant. Only 2m of the panzer height is visible. 0.70 seconds to 600m 0.95 seconds to 800m CASE 1 Firefly gun is 2m above panzer aim point (3m above bottom and 1m above top). 0.317 degree setting for 800m shot using simple trig model. Angle from Firefly to center of panzer is -0.191 degrees. Trajectory height at panzer equals: 2m + 600m x tangent (0.317 - 0.191) - 0.5 x 9.81 x 0.70squared, or 0.92m above target center. CASE 2 Firefly gun is -2m below panzer aim point (1m below bottom and 3m below top). 0.317 degree setting for 800m shot. Angle from Firefly to center of panzer is +0.191 degrees. Trajectory height at panzer equals: -2m + 600m x tangent (0.317 + 0.191) - 0.5 x 9.81 x 0.70squared, or 0.92m above target center. Son of a gun, same result whether 17 pdr is 2m above or 2m below the aim point. Just as I been saying, makes no difference if gun is a few meters this way or that. As an aside, the math model we use to predict the impact of range estimate errors predicts that 17 pdr APCBC fired at 800m against a 600m target will reach the target 0.85m over the aim point regardless of relative height (gun vs aim point). As stated in the last post, the impact of upward and downward air resistance is not considered in the simple model I used and actual trajectories will be a tad lower (0.85m vs 0.92m).

Jeff, Regardless of barrel height, aim at target bottom with the same range setting on the gun results in the same trajectory height at the target. The example I presented shows this. Now, let's go one step further and look at the case where a Tiger sees a 4 mil high T34 and aims the gun for a 750m shot based on the perceived height, but the actual range is 500m. The T34 is only 2m above ground due to dips and folds and looks 4 mils high, so a 750m range estimate results. CASE 1 Tiger gun is 2m above T34 bottom. Tiger aims gun at target bottom, angle is -0.229 degrees. Tiger sets gun elevation for a shot of 750m + 4 x 1/2 x 100m or 950m. Elevation angle is 0.465 degrees. Final angle = 0.465 - 0.229 = 0.236 degrees Trajectory height at 500m T34 equals: 2m + 500m x tangent (0.236) - 0.5 x 9.81 x 0.66squared = 1.92m above target bottom CASE 2 Tiger gun is -2m below T34 bottom. Tiger aims gun at target bottom, angle is +0.229 degrees. Tiger sets gun elevation for a shot of 750m + 4 x 1/2 x 100m or 950m. Elevation angle is 0.465 degrees. Final angle = 0.465 + 0.229 = 0.694 degrees Trajectory height at 500m T34 equals: -2m + 500m x tangent (0.694) - 0.5 x 9.81 x 0.66squared = 1.92m above target bottom So there we have it, regardless of what type of aim (Battlesight or aim at bottom with adjusted range estimate), and regardless of how high or low the Tiger is with regard to the T34, THE ROUND REACHES THE T34 AT THE SAME TRAJECTORY HEIGHT ABOVE TARGET BOTTOM. Because we are discussing the effects of Tiger gun elevation upon the accuracy of the rounds, and meaning no insult, let me state that I am not interested in examples with rifles and will not really look very closely at the results. If someone else will run a trajectory program for the above examples and present the results here it would be good for comparison purposes; I already did the computer runs and the results support the conclusions in this and my preceding post on this thread. [ September 12, 2004, 02:39 PM: Message edited by: lorrin ]

With all due respect to Jeff, something about his analysis does not seem correct. We're talking about battlesight aim where the Tiger doesn't care what the range to target is as long as it is less than the gun setting of 800m to 1000m. I've posted several examples on this thread where a Tiger aimed at the bottom of a target at 200m and elevated the gun for a 1000m shot, and the round reached the target at the same height above target bottom whether the Tiger gun was 2m above target bottom or 0.5m below. Let's do a simple example for the doubting Thomas's out there, and we'll use a simple trigonometric model that doesn't require access to complex ballistic programs (there will be a small error in the details but the overall conclusions stll hold). CASE 1 Tiger gun is 2m above bottom of T34, T34 is at 550m from Tiger and Tiger commander couldn't care less what the actual range is. Aim at bottom of T34, so gun is depressed -0.208 degrees, Set gun for 1000m shot, so gun is elevated 0.50 degrees above initial aim at target bottom. End result, gun is elevated 0.292 degrees above horizon. What is height of round at target? 2m (gun height) + 550m x tangent (0.292) - 0.5 x 9.81 x 0.72 squared or 2.26m above target bottom. CASE 2 Tiger gun is -1m below bottom of T34, T34 is at 550m from Tiger and Tiger commander couldn't care less what the actual range is. Aim at bottom of T34, so gun is elevated +0.104 degrees, Set gun for 1000m shot, so gun is elevated 0.50 degrees above initial aim at target bottom. End result, gun is elevated 0.604 degrees above horizon. What is height of round at target? -1m (gun height) + 550m x tangent (0.604) - 0.5 x 9.81 x 0.72 squared or 2.26m above target bottom. CONCLUSION For battlesight aim, height of gun relative to target bottom doesn't make a hill of beans of difference as long as the initial aim is at target bottom and the subsequent elevation rise fo range setting is the same. The real trajectory will be a little lower since air resistance resists the initial upward motion and then resists the downward motion.

Thanks for photo and drawing. Do we know for sure that German tank commander binocs had mil markings (lat and vert) on them: it may have been discussed before but I don't recollect the answer right now.

Thanks for photo and drawing. Do we know for sure that German tank commander binocs had mil markings (lat and vert) on them: it may have been discussed before but I don't recollect the answer right now.

Mr. Tittles: The Churchill trials reveal alot more than you referred to in your last posts, and you might wish to study the results more closely along with my analysis of the data. 6 pdr APCBC has a larger dispersion than the Tiger 88L56 APCBC, and one would expect that Churchill firing trials against a 2' x 5' target would result in a lower hit probability than the Tiger. The three best Churchills had an average hit percentage HIGHER than the 88L56 at three of the ranges: 500 yards 89% for 3 best Churchills, 96% for Tiger 800 yards 84% for 3 best Churchills, 83% for Tiger (even though the difference is small, the expected difference should be reversed and much larger) 1000 yards 81% for 3 best Churchills, 75% for Tiger 1500 yards 62% for 3 best Churchills, 54% for Tiger If the three best Churchills outperformed the Tiger at 800 yards through 1500 yards, it follows that the worst two Churchills would be expected to perform significantly worse than the average 6 pdr even if their crews and bore sighting were perfect. There is a limit to how good one can make a weapon system using bore sighting, good crews, etc., and the best explanation for the three Churchills is better than average guns. And one would then expect less than average performance from below average guns. With regard to the German expectations for accurate guns, the 75L48 APCBC clearly fails to meet the criteria as does the 88L56 APCBC if my calculations are correct.

Couldn't make out at first what your point was about the same guns. I think you forgot the Churchill trials and what they suggested. The British firing tests with 6 pdr Churchills show that wide differences are possible in the performance of the 6 pdr guns in different tanks. Whatever the cause, the German data is an average and some will be higher, some will be lower. Ditto for German APCBC penetration. Quality control tests show a 24% difference in the velocity needed to defeat a given plate, as measured from high to low. The Churchill trials show some guns with about 50% of the average dispersion, others with almost 200% of the average. I bet that rifles have unique characteristics if one goes from one to another. Some may pull more to the right, or tend to shoot high for the same aim, etc.

Good point. The 50mm L60 and 88mm L71 guns fired at the same velocity, while the 75L46 Pak 40 and 75L48 fired at different velocities. The above statement suggests that the 75mm L46 Pak APCBC would have the same dispersion characteristics as the 75mm L48? The answer to that question would be very interesting.

"Actually I just read that German manufacturing of the guns led to very similar performance between guns of the same type. There would not be such a wide performance between guns of the same type as you claim." Michael did not claim anything, he quoted official statistics. If the data suggests that the Flak gun had a wider dispersion than the tank gun, there may well have been some good reasons that we are either not aware of or don't realize the importance. "As far as 100% dispersion, I would be happy just to see a 10 round shot group. I would want to see the real data instead of the 50% data." A 10 round shot group has the potential of including alot of extreme scattering or close scattering that is not representative of the true average. 50% zones are real data, you are looking for the individual data points. The conversion of the 90% zone data for 17 pdr APCBC to 50% zone numbers shows that the German 50% zone figures are reasonable and realistic. While you may continue to search for the holy grail (individual data points for German dispersion tests) I am finished discussing the issue. 50% zones are REAL DATA and are averages of many guns and many rounds by many different makers on many different days.