Getting the best mileage from the squeeze-bore guns? (4 Viewers)

[Shortround6]

A couple of ideas for the moment

Make the APCBC type of shot for the squeeze bore guns.

Some of them were already of that type/style. Or at least they used a sort of ballistic cap. Need for a penetrating cap on a cored shot using tungsten carbide is minimal.
Using APCBC on a steel core would make sense. Depends on impact velocity. Too high defeats the penetrating cap.

British got the big gain in 2pdr ammo because the shape of the normal AP shot was so crappy. Pointy nose allowed for a significantly higher impact velocity with no increase in propllent charge or muzzle velocity

That, and avoiding the 28/22 being made, will improve the ammo supply for the more powerful guns.

Again this all depends on the goals.
From Wiki so............
The sPzB 41 was used by some motorized divisions and by some Jäger (light infantry), Gebirgsjäger (mountain) and Fallschirmjäger (paratrooper) units. Some guns were supplied to anti-tank and sapper units.
So while some seem to have been put in units that could have used larger guns the Jäger, Gebirgsjäger, Fallschirmjäger units needed, or wanted, a lighter/higher performing gun than the standard 37mm. Or the 7.9mm AT rifle or the existing rifle grenades. I don't know if this was a legitimate requirement or not but if it was, what path can be followed in 1940-41 to get better AT weapon for the light troops?

 

[tomo pauk]

The sPzB 41 was used by some motorized divisions and by some Jäger (light infantry), Gebirgsjäger (mountain) and Fallschirmjäger (paratrooper) units. Some guns were supplied to anti-tank and sapper units.
So while some seem to have been put in units that could have used larger guns the Jäger, Gebirgsjäger, Fallschirmjäger units needed, or wanted, a lighter/higher performing gun than the standard 37mm. Or the 7.9mm AT rifle or the existing rifle grenades. I don't know if this was a legitimate requirement or not but if it was, what path can be followed in 1940-41 to get better AT weapon for the light troops?

Depends on how powerful the gun is really supposed to be, and whether the use of tungsten is allowed or not. Also, what quantity is really required? Instead of ~2800 of the 28/22 manufactured, perhaps just 1000 was the actual need before the 'classic' guns could fit the bill?
Several options might be viable with tungsten, that might mimick the AP performance of the 28/22:
- 47mm Bohler, that was also produced for the German needs. Ballistics were similar to the French 47mm on the tanks, or about 20% weaker than the Czech AT gun. Going APCR here gives maybe 50mm at 500 m v 30 deg (vs. the Czech gun doing 59mm under these conditions). That is actually much better than the 28/22, that did just 40mm there. Combat weight is very light, 60 kg greater than on the 28/22, and 50 kg lower than of the 37mm ATG.
- Czech or German 37mm ATG with the good muzzle brakes and on the light carriages.
- 30mm, firing the APCR ammo for the MK 101.
- The 25mm with APCR - 50mm at 100m at 30 deg - and on a light carriage (the gun was heavy for it's calibre - 200 kg heavier than the Bohler, and twice the weight of the 28/22)

Either of these should be under 300 kg.

Less convential guns possible, no tunglsten needed:
- Breech-loading mortar of 60 or 50mm cal; the 60mm barrels are basically free now. Japanese gotten to almost 200m/s with their 200 kg 70mm gun.
- Steil granate, but don't over-do it.

Rifle grenades will work, accuracy and range will be more of a problem. A big advantage is that almost any soldier armed with a rifle can do it.

 

[z42]

A good 20mm AP round of some type could have been developed by the French for their 20mm HS aircraft guns. Possibly an extremely good AP round.

The British standard 20mm AP for most(?) of the war was the AP Mk II. It could reliably penetrate 36mm/31mm of typical German tank armour, at 0°/20° from normal, at 400 yds, when fired from an aircraft with a forward velocity of 238 mph (ie at Hurricane Mk IIC max speed on the deck at 2850 rpm and +9 lb boost ). The AP Mk III would in theory (I am not sure if it entered service or was used to any extent if it did) have been even more capable, with a penetration of 51mm/44mm when fired under the same circumstances at the AP Mk II. I believe this is enough to deal with the side, rear, and top armour on German early-war tanks up through the PzKw IV? While the British 20mm AP rounds were not crude, they were not in any way exotic.

What could the French have developed with their ideas/knowledge of HVAP and APDS?

The GAU-8 cannon on the A-10 uses APCR rather than APDS because they figured that sucking sabots into the engines wasn't conductive to the long-term health of the aircraft. Somewhat equal ballistics with HE ammunition may also have been a consideration, when both are loaded into the magazine (which I would guess is the usual load?)? Granted prop planes don't have the large exposed fans of turbines, and speeds are lower, but I suspect the sabots would still be capable of damaging the aircraft.

 

[z42]

But it has been said many times: before the GAU-8/A, all aircraft cannons used against tanks were extremely ineffective due to the high shell dispersion and the instability of the aircraft when firing.

I believe accuracy was still an issue on the original A-10A, considering for the A-10C they introduced a gee-wiz computer system to keep the nose pointed on the target while firing. Still, much less so than mounting some massive 35+mm gun on a comparatively tiny WWII aircraft. And even without the gee-wiz system I guess it still had gun radar etc. which obviously wasn't an option in WWII.

 

[bf109xxl]

I believe accuracy was still an issue on the original A-10A, considering for the A-10C they introduced a gee-wiz computer system to keep the nose pointed on the target while firing. Still, much less so than mounting some massive 35+mm gun on a comparatively tiny WWII aircraft. And even without the gee-wiz system I guess it still had gun radar etc. which obviously wasn't an option in WWII.

Exactly! One large cannon with a low rate of fire, mounted on an aircraft of the size of a single- or even twin-engine fighter/attack aircraft from World War II, is not the solution to the problem. A battery of 3-4 heavy guns on a heavy twin-engine attack aircraft may be a solution (I'm not sure about that!), but there was only one such aircraft, and it did not participate in combat.
The Soviets conducted numerous field tests with different guns and different aircraft, and even with pilots of different training levels. The conclusions were rather disappointing. Tank loss statistics confirm these conclusions - this has also been mentioned here repeatedly (in particular by Dimlee).
Only the installation of a super-fast gun with high-penetration shells on a much heavier jet attack aircraft with complex electronics increased the effectiveness of the gun to a somewhat acceptable level.

 

[Shortround6]

Getting back to a small AT gun, the Swiss had the 24mm Tankbüchse 41.
Which shows it's easy transport.

Although one wonders what the bicyclist looks like after 10-15km
225g projectiles at 860/900mps (sources differ). Gun is semi-auto but has a 5/6 round magazine.
Gun may have been able to penetrate 30mm at 200 meters sloped the usual 30 degrees.

The gun does address one of the overlooked aspects of small AT guns.
There are 3 stages of tank killing.
1. hit the tank, low velocity guns suck at this.
2. penetrate the armor. This gets by far the most attention and little more needs to be said.
3. cause damage behind the armor, fire/crew casualties/damaging equipment like engine, transmission, gun or turret mechanism.
This gun with the magazine/s has a higher rate of fire for repeat shots. Gun also auto-ejects the magazine after the last round goes in the chamber so the gunner/s do not have to manually cock the gun after a magazine change. Assuming the gun can actually penetrate the target tank the gunner may be able to score 3-4 hits in 6-10 seconds Using 1-2 to just get on target.
The HE ammo was in 5 round magazines so the gunners could tell them apart. HE content not given but assuming around 10% that gives about double the HE of 20mm shell or 4 times that of the German 28/20 gun. Not a 37mm gun but with that semi auto rate of fire 3-5 24mm HE rounds might keep the enemies heads down.

Love these posed photos with one crewman sitting on another crewman

 

[tomo pauk]

Getting back to a small AT gun, the Swiss had the 24mm Tankbüchse 41.
Which shows it's easy transport.
Although one wonders what the bicyclist looks like after 10-15km
225g projectiles at 860/900mps (sources differ). Gun is semi-auto but has a 5/6 round magazine.
Gun may have been able to penetrate 30mm at 200 meters sloped the usual 30 degrees.

A gun like this would've been good for plinking the German tanks in 1939-40. Usage by anyone past 1940 will be a dubious move, especially for the Germans. The 28/22, for all it's shortcomings, was offering more than 50% better penetration.
On a flip side, this gun shows just how light the full-power 25-30mm guns (like the French 25 ATG, or the single-shot MK 101/103, or the 1-shot French AA gun) might've been when tailored if tailored towards the lightness, with or without the semi-auto feed system.

 

[special ed]

Getting back to a small AT gun, the Swiss had the 24mm Tankbüchse 41.
Which shows it's easy transport.
View attachment 858878
Although one wonders what the bicyclist looks like after 10-15km
225g projectiles at 860/900mps (sources differ). Gun is semi-auto but has a 5/6 round magazine.
Gun may have been able to penetrate 30mm at 200 meters sloped the usual 30 degrees.

The gun does address one of the overlooked aspects of small AT guns.
There are 3 stages of tank killing.
1. hit the tank, low velocity guns suck at this.
2. penetrate the armor. This gets by far the most attention and little more needs to be said.
3. cause damage behind the armor, fire/crew casualties/damaging equipment like engine, transmission, gun or turret mechanism.
This gun with the magazine/s has a higher rate of fire for repeat shots. Gun also auto-ejects the magazine after the last round goes in the chamber so the gunner/s do not have to manually cock the gun after a magazine change. Assuming the gun can actually penetrate the target tank the gunner may be able to score 3-4 hits in 6-10 seconds Using 1-2 to just get on target.
The HE ammo was in 5 round magazines so the gunners could tell them apart. HE content not given but assuming around 10% that gives about double the HE of 20mm shell or 4 times that of the German 28/20 gun. Not a 37mm gun but with that semi auto rate of fire 3-5 24mm HE rounds might keep the enemies heads down.
View attachment 858879
Love these posed photos with one crewman sitting on another crewman

There is level ground in Switzerland? Where is the photo of him riding uphill pulling the gun?

 

[bf109xxl]

There is level ground in Switzerland? Where is the photo of him riding uphill pulling the gun?

Shhh! That will ruin the whole concept.

 

[Elan Vital]

About weight considerations, there is the case of the French 25mm.

The original Hotchkiss SA34 weighed 480 kg and was initially suitable only for low speed (horse) traction - up to 15 kph -, later improved to medium speed traction -35 kph - around the 2000th gun made.

The APX SA-L 37 had a much lighter carriage reducing total weight to 310 kg, but was more fragile so limited to 15 kph traction like the early SA34, with the reduced weight nonetheless helping the horses and gun crew a lot.

The Levallois factory's (nationalized Hotchkiss) SA 34 Modifié 1939 which was adopted in early 1939 and just coming in production in June 1940 was lightened (lighter steels, lighter and simpler shield, muzzle brake to cope with the recoil even at reduced weight while also reducing recoil length from 240 to 200mm), but also made suitable for high speed traction: 70 kph in manuals and up to 85 kph in testing. 370 kg, so 60 heavier than the slow-traction SA-L 37 but 110kg lighter than the slow/medium-speed traction SA34.

For comparison, the 37mm PaK 36 with similar armor piercing capability weighed 450kg (327 in combat).

 

[Shortround6]

A gun like this would've been good for plinking the German tanks in 1939-40. Usage by anyone past 1940 will be a dubious move, especially for the Germans. The 28/22, for all it's shortcomings, was offering more than 50% better penetration.
On a flip side, this gun shows just how light the full-power 25-30mm guns (like the French 25 ATG, or the single-shot MK 101/103, or the 1-shot French AA gun) might've been when tailored if tailored towards the lightness, with or without the semi-auto feed system.

True but the Soviets were using thousands of T-26s, BT-7s and T-60s well into 1942. Production of T-70s continued into 1943. Although the T-70 is a lot tougher on the front.
For world wide use see Italian, Japanese and even American light tanks (M3 Stuart). Nobody expects light AT guns to stop heavy tanks. Light AT guns that can stop light tanks/recon cars can buy several hours to get larger AT guns into position, assuming such guns are close to the contact point.
The Swiss gun (or any 24-28mm high velocity gun) is going to have close to the same performance of the 28/20 at longer ranges (500-1000 meters) and have better HE capability (although still very small)

The 28/20 is sort of a super Anti-tank rifle.

Wiki say (better source?) core was 10mm in diameter and 40mm long.
And this is problem with No 3 in the list in post #46. It is not enough to make a 10mm hole in the armor of a tank. You have to damage/destroy stuff inside the tank. Even in NA in 1941/42 British 2pdrs and German 37mm and 50mm guns often needed several penetrating hits before the crew (survivors) abandoned the vehicles. Which sometimes lead to "over killing" keep shooting at a tank until the crew was seen to bail out or smoke/flames came out. Maybe the tank was already dead and the firing tank was wasting effort instead of engaging a 2nd target. Making a 25mm hole means a lot more stuff (metal fragments) flying around inside the tank than a 10mm hole and obviously making 40-50mm holes really means a lot stuff. But still a fraction of a 75mm shell.
It all on a sliding scale and no size shell (until you get really, really big) guarantees a kill with penetration.

The problem with the 28/20 is that after the shell gets squished down you basically have 20mm 125g projectile with a decent (but not great nose) and a not good tail. It starts out fast but it slows down quickly. So do most small projectiles.

Pluses to the 28/20 is the good short range performance and the light weight.

 

[tomo pauk]

True but the Soviets were using thousands of T-26s, BT-7s and T-60s well into 1942. Production of T-70s continued into 1943. Although the T-70 is a lot tougher on the front.

You want a gun for the paratroopers, mountain infantry and the like. These troops represented perhaps 1% of all of the german infantry units, and perhaps 0.1% of the German infantry units in the Eastern front. Worrying that they have a perfect AT gun would've been a waste of German production capabilities and tungsten. Regular infantry has thousands and thousands of the 37mm stuff, that will handle these tanks, even without tungsten.
If you insisist - and it seems so - the tanks you've listed were a perfect target for the 25mm French gun (or even for the 20mm). Stick these on a light carriage and the Jaegers will have a field day.

For world wide use see Italian, Japanese and even American light tanks (M3 Stuart). Nobody expects light AT guns to stop heavy tanks. Light AT guns that can stop light tanks/recon cars can buy several hours to get larger AT guns into position, assuming such guns are close to the contact point.
The Swiss gun (or any 24-28mm high velocity gun) is going to have close to the same performance of the 28/20 at longer ranges (500-1000 meters) and have better HE capability (although still very small)

Swiss gun is, for the German military, a solution in search of a problem. Especially past 1940.
If a 37mm cannot make it, a solution is not to go design and produce an even worse gun, not even to buy it from the other countries. Solution is a more powerful gun, firing either AP ammo of sorts, or HE.

The problem with the 28/20 is that after the shell gets squished down you basically have 20mm 125g projectile with a decent (but not great nose) and a not good tail. It starts out fast but it slows down quickly. So do most small projectiles.

Pluses to the 28/20 is the good short range performance and the light weight.

I've agreed long time ago that the 28/20 is a bad deal.

 

[Shortround6]

Going back to No. 3 again. Heat shells don't have a lot of killing power inside a tank unless they really overmatch the armor.
British No 68 rifle grenade.

Now since the "effective" range was only about 70 yds and the troops were advised to let the tanks pass them by and shoot at the rear of the tank for best results this is still a last ditch weapon. Better than running up to a tank and throwing an explosive charge on the back but not much. Also note the rather dodge position, firing from the shoulder was strongly discouraged to prevent injuries. They were also not to be fired from standard service rifles as they tended to break stocks. This thing was fin stabilized and about 2 1/2 in diameter and good for about 2in (52mm) of penetration if it hit correctly. The Warhead, being among first of it's kind was very basic and poor performing as were most of the early WW II shaped charge weapons.
Early shaped charges also tended to taper.

Blast released into tank in the last 25-30% of the penetration is nowhere what the happens in the first 1/3. Not saying there are no deaths/injuries but a rifle grenade or small artillery shell is not quite as lethal as some people imagine.

 

[Shortround6]

You want a gun for the paratroopers, mountain infantry and the like. These troops represented perhaps 1% of all of the german infantry units, and perhaps 0.1% of the German infantry units in the Eastern front. Worrying that they have a perfect AT gun would've been a waste of German production capabilities and tungsten. Regular infantry has thousands and thousands of the 37mm stuff, that will handle these tanks, even without tungsten.
If you insisist - and it seems so - the tanks you've listed were a perfect target for the 25mm French gun (or even for the 20mm). Stick these on a light carriage and the Jaegers will have a field day.

I actually agree with you. Just trying to point out the German thinking. The Germans designed and built a huge amount of rather interesting but not practical military "toys" that sucked up engineering and manufacturing capacity.
Problem with the French guns are two fold.
1, Not invented here ( a real problem for the Germans in a lot of ways)
2, capturing a crap load of decent/serviceable stuff right after several years of research/development seems to pay off. Make the arms companies happy by issuing production contracts or tell them, sorry boys---to late---we are just going to use all this free captured stuff

The rational for the 28/20 at least had some merit, even if not much. The 42/28 has a even less. Design a 45/47mm barrel for the 37mm gun carriage, slap a big muzzle brake on it, re-barrel worn out 37mm AT guns. Or adapt/issue captured Soviet 45mm AT guns. Maybe not great armor punchers but a lot better at HE support which is were a lot of the old 37mm guns went.

Using guns with abnormally high barrel wear like the taper bore guns for HE support seems to rather stupid.

 

[tomo pauk]

The Germans designed and built a huge amount of rather interesting but not practical military "toys" that sucked up engineering and manufacturing capacity.
Problem with the French guns are two fold.
1, Not invented here ( a real problem for the Germans in a lot of ways)
2, capturing a crap load of decent/serviceable stuff right after several years of research/development seems to pay off.

That is what I'm trying to say all the time - if a new gun (or a gun + ammo combination) is having problems with the tanks of today, it represents the bad use of money, time and resources. Just wasting one of that is a sin in any sane military; wasting all 3 inn the same time deserves the straight jacket.
Germans had no problems of using the captured equipment, but they seem to indeed were favoring their own gear, both for use and possible continuation of production. Served them right.

The rational for the 28/20 at least had some merit, even if not much. The 42/28 has a even less. Design a 45/47mm barrel for the 37mm gun carriage, slap a big muzzle brake on it, re-barrel worn out 37mm AT guns. Or adapt/issue captured Soviet 45mm AT guns. Maybe not great armor punchers but a lot better at HE support which is were a lot of the old 37mm guns went.

Germans going for their own 45-47mm design has a bad timing, IMO, unless it is done before the 5cm AT gun. After 1938, there is a good deal of captured 47mm stuff to go around, don't reinvent the wheel.
Using the captured 45mm is a no brainer.

 

[Shortround6]

Germans going for their own 45-47mm design has a bad timing, IMO, unless it is done before the 5cm AT gun. After 1938, there is a good deal of captured 47mm stuff to go around, don't reinvent the wheel.

A bunch of people used the German 37mm carriage and some of them mounted new barrels on them. Not hard as the German 37mm was one of the weaker non French 37mm guns around.
Perhaps there was room for a 45-47mm gun that fit between the 330kg 37mm and the 970-1000kg 5cm Pak 38?
Although it might be hard to beat the Czech 4.7cm at 590kg.

 

[tomo pauk]

A bunch of people used the German 37mm carriage and some of them mounted new barrels on them. Not hard as the German 37mm was one of the weaker non French 37mm guns around.

My long-time cunning plan is that the 37mm barrels end up as the future barrels of the automatic guns to kill aircraft
That leaves a lot of carriages looking for a new job. Some of them actually had the short 75mm installed, so there is an idea. It also shows how these carriages were actually over-built.

Perhaps there was room for a 45-47mm gun that fit between the 330kg 37mm and the 970-1000kg 5cm Pak 38?
Although it might be hard to beat the Czech 4.7cm at 590kg.

Last sentence is bang on the money.

 

[Shortround6]

That leaves a lot of carriages looking for a new job. Some of them actually had the short 75mm installed, so there is an idea. It also shows how these carriages were actually over-built.

True but the short 75mm was actually a pretty poor AT gun and it also shows the problem with trying to figure out what German HEAT shells could do when.
The first HEAT round used in the IG 18 (same ammo as the IG 37) in 1940-41 was only good for about 45mm of penetration at 30 degrees. Later shell (when?) was better.
1st 10.5cm Howitzer round was good for a lot less than 100mm of penetration. Things got better on designs 2, 3 and 4 (around 100 mm of penetration) Penetration sort of reached a plateau but the later shells require less explosives for the same performance.
I don't know when the HEAT round became a really viable AT round out of a rifled gun. 1941 or 1942 or 1943?
And that is just for penetration, hitting things with shells leaving the muzzle at 325m/s at best (could be around 280ms?) means it was a short range gun a best.

 

[tomo pauk]

True but the short 75mm was actually a pretty poor AT gun and it also shows the problem with trying to figure out what German HEAT shells could do when.
The first HEAT round used in the IG 18 (same ammo as the IG 37) in 1940-41 was only good for about 45mm of penetration at 30 degrees. Later shell (when?) was better.
1st 10.5cm Howitzer round was good for a lot less than 100mm of penetration. Things got better on designs 2, 3 and 4 (around 100 mm of penetration) Penetration sort of reached a plateau but the later shells require less explosives for the same performance.
I don't know when the HEAT round became a really viable AT round out of a rifled gun. 1941 or 1942 or 1943?
And that is just for penetration, hitting things with shells leaving the muzzle at 325m/s at best (could be around 280ms?) means it was a short range gun a best.

The short 75mm on the 37mm carriage is not an AT gun, but an infantry gun with a secondary AT capacity, that could come in handy if the enemy tanks somehow eluded the proper AT means. Short 75mm fired HEAT shells at almost 400 m/s.

Another way of using left-over 37mm carriages might've been to make a breech-loading mortar for them. Nothing fancy as the paw 600, just something to fire the mortar and HEAT shells in the low register.

 

[Shortround6]

The short 75mm on the 37mm carriage is not an AT gun, but an infantry gun with a secondary AT capacity, that could come in handy if the enemy tanks somehow eluded the proper AT means. Short 75mm fired HEAT shells at almost 400 m/s.

The almost 400m/s performance doesn't show up until late in the war. A substitute for the taper bore guns needs to be ready in 1940/early 41.
The IG 18's first HEAT shell was the one that had 260m/s velocity and had the 45mm at 30 degree performance. Used a powder charger of 71g.
It took a powder charge of 100g to get to 345m/s. Use of the longer barrel on the IG 37 may have made up the difference to 389ms (or higher) and there is no technical reason why a longer barrel could not have been used in 1940/41.
Might work for defending the gun/s themselves. Doesn't work for defending the battalion/regiment. The regiment had a dedicated AT gun unit.
The standard 3.7cm Pak 36 was good for
round..................Pzgr..........Pzgr 40
100m..................65/50.........79/68
500m..................48/36.........50/40
armor at 0/30 degrees

This is one weapon that the Germans did not get too tricky with. With a MV of 762m/s it had a decent effective range (distance at which it could hit with the 1st or 2nd round) of over 750 meters. The Pzgr 40 has flatter trajectory but as can be seen penetration was dropping to almost no advantage over 500 meters. Accuracy is not reported in most English language sources.
The standard Pzgr was uncapped, either ballistic or penetrating and had small HE charge and fuse in the back of the shell. Assuming the fuse functioned there was 13g of HE to help wreck things/kill, wound crew behind the armor and not depend on the shot itself and the pieces of plate from the hole bouncing around inside the tank.

This are performance 'goals' that have to met/exceeded to consider substitutes.
Germans never used a "super charge", nor improved (capped, in either way) shells or just used solid shot.
Maybe they were too busy designing "trick" guns. It is for sure that they had not exhausted conventional technology.
American 37mm AT guns fired AP rounds that were 28% heavier (no HE) and better shaped (only a little bit with M74) and about 120m/s faster.
US also used a APCBC shot of the same weight and speed which significantly increase penetration at longer ranges (3-400yds and above).

Another way of using left-over 37mm carriages might've been to make a breech-loading mortar for them. Nothing fancy as the paw 600, just something to fire the mortar and HEAT shells in the low register.

You could but why? If it is not as fancy (gun, not mount) as the PAW 600 you don't get anywhere near the range, either max or practical. You need the larger propelling charge and longer barrel to get the higher velocities. The performance of the PAW 600 is going to generate about 3 times the recoil force of the 3.7cm Pak 36.
There is no reason it could not be done but firing the 8cm AT shell at even 260m/s is still about 1.5 times the recoil force of the 37mm gun. Maybe the 37mm is overbuilt but by how much? and 260-350ms AT shells pretty much suck. The muzzle launched stick bombs really sucked, require much closer than max book ranges to actually hit and very little chance of a second shot.
Simple ballistics
time..................shot fall
1 sec...................4.9 meters
2 sec.................19.6 meters
3 sec.................44.1 meters
4 sec.................78.4 meters

Now you can elevate the gun and at close range if you aim about 1.6 meters at 150 meters high you may be able to lob the shell onto at tank at the end of 1 second of flight.
At ranges that require 2 seconds of flight you need to aim over 6 tanks high. At 3 seconds of flight the tank better be parked next to 15 story building in order to judge how high to aim. And 3 seconds of flight is under 1000 meters of distance for our 360ms HEAT round. Stick bomb on the 3.7cm Pak with it's 110ms velocity is supposed to be good for 300 meters effective according to some sources. I think that manual was written by Goebbels when his drugs were peaking.

Mortars have the advantage of being able to fire out of pits or behind walls or small hills and are immune to return direct fire. Granted they give up some accuracy. But using breech loading smooth bores in a direct fire role, while there are some advantages, there are also a number of disadvantages, like getting the crew shot. The gun shield was suppose to protect against 8mm fire at 500 meters or more. At close range things get more difficult and the shield was not big enough for the entire crew. Walls, ditches, sandbags, piled up rocks all helped.

I am liking the Czech 4.7cm gun more and more. Put it in the 3.7cm carriage (better muzzle brake?) and work on better ammo (APCBC?). It will never be a KV killer but it can shoot at other battle field targets from hundreds of meters further than the normal IG or smooth bores. Granted the HE ammo is smaller you are trading distance/safety.