Tanks thread?

No. Only the Israelis and Egyptians ever fitted 'modern' powerful guns to the Sherman. And it took some doing.
Yes. There was a version with a 105 mm howitser during WW2. It was called the M4 105.

Normal armament was a 75 mm gun that varied somewhat in barrel length between version.
It was close to OK to engage German tanks with. Nowhere near as impotent as Hollywood movies (like Fury) and legends make it. It depended on the angle (towards the armor surface), but German tanks were not safe within 1000 m, and certainly not within 100 m.

Still, it wasn't exactly good against Tigers, so the Brits spent some time figuring out how to fit their 17-pounder anti-tank gun in the Sherman. This became the famous Firefly Sherman, which generally didn't have much problems to plink German tanks. The 17-pounder gun was a 76 mm high velocity gun.
USA worked on fitting a somewhat similar gun, the 76 mm gun. This was made more practical by using a bigger turret. Late versions of the Sherman had this gun, which is easily recognizable due to the different turret, longer barrel and muzzle brake.  Old turret with long barrel and muzzle brake = Firefly.

The French 75 mm gun, which both Israel and Egypt later equipped Shermans with, is a much more powerful gun. The Egyptians swapped the entire turret to the French AMX-13 turret with the gun. The Israelis added a noticeable counterweight on the backside of the turret.

The 105 mm gun of the Israeli Sherman M51 was an extreme and unique modification, but was possible because the Israeli Shermans had gained a good deal of weight, and then there was the bigger turret.

The next British tank gun was their 20-pounder, a 84 mm gun that they fitted to their Centurion. Israel bought, traded or hijacked old Centurions, but soon replaced the 84 mm with a 105 mm gun, the British L7 gun, which was fitted to more modern Centurion tanks and eventually became a sort of Western standard tank gun. The L7 is much heavier and more powerful than the french lightweight 105 which the Israelis had fitted to their Shermans. The Israelis also replaced engines, transmission and other equipment in their Centurions, creating their "Sho't" tank. They eventually also upgraded the steel armor, finally also adding reactive armor.

Couldn't it just be the howitzer version? Looks pretty much like a normal Sherman.

if I recall my history correctly that "upgrade work" was undertaken due to problems over ammo production licencing prices, also a lot of decent gear has been through some sort of life extension program in order to extend its usefull life period, for instance the ubiquitous "Bedford truck" that first entered service in the 1930's many of them didnt get retired until the late 1990's they just went to 3rd line repair units and had bits changed... the first "transporter truck" I drove was actually an old Bedford tractor unit built in 1939 (although it had had its engine and gearbox upgraded twice) when I was doing aircraft recovery and helicopter delivery jobs in 1998 (that tractor unit didnt get replaced until the man units came out in 2008) although to be fair nobody liked using it, the cab was too low down, it had the take off speed of a snail and it climbed hills so slowly that often times the co driver would hop out for a walk to reduce some of the weight burden.... (yeah it really was that bad) of course that means as a new HGV driver with a 108ft long trailer it wasn't a bad rig to plod about in  

wasn't the only such vehicle either, I mean there were plenty of ancient movers however what made me really laugh was that the UK flogged all of them to foreign powers (mostly in south America and Africa) even the original 1945 "landrover" units that had been "modernised" got flogged (yes I know landrover as a company was only formerly created in 1949, however it was a government company that produced military vehicles from about 1920 onwards under a different name) 

military history is replete with such narrow thinking though, whilst a civi company will happily replace its fleet every decade governments are far more miserly, they will happily spend billions on road projects but a few hundred million every 20 years for a new vehicle fleet forget it....they rather spend twice as much training mechanics and buying spares to keep them going....

Before the Merkava, there were the Magachs.

During the 1973 Yom Kippur war, the Israeli defense force operated a large number of American Patton tanks, of various ages and versions from various sources. M48s and M60s.
They suffered badly from Soviet anti-tank missiles during the war. Centurion derived tanks suffered about the same relative losses, but there was something with the Pattons that went down very badly with the Israelis. The flammability of the hydraulic system.

When the surviving and replacement M48s and M60s were upgraded in the usual Israeli fashion, new everything, they did two additional things, fixed the hydraulic system and deviced a system of reactive add-on armor, "Blazer" which they also fitted to their Sho't tanks (Upgraded Centurions).
Magach 5 (based on M48A5)
Magach 3 (based on earlier M48 models)


Magach 6B (based on the M60A1) (Magach 6C are M60A3 upgraded to Magach 6B standard)


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Magach 7 (based on the M60)


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Magach 6B Gal Batash, sometimes aka Magach 8 (based on the M60A1)

Was unable to link a picture here, but the 6B Gal Batash are the ones that get a Merkava 4'ish looking turret. It's just add-on on the old turret, like the Magach 7. The add-on is partially reactive again, even if it doesn't look it.

The Magachs were mainstay during the invasion of Lebanon in 1982, and survived the hits of anti-tank missiles, proving the concept of reactive armor.
Looking for more protection also against kinetic tank projectiles, Israel decided to develop the Merkava.

And then there was the Merkava. I didn't have to do any work. There's a good video.

Trash comment:
Apparently our tank (TAM) is the fastest in the world (as of now). Imagine my shock, being first place at something.
There has been an in going joke here for a while about we being at second place in everything, even inflation (thanks Venezuela). Hooray.

(13:52)

I wouldn't be surprised if an Imperial Japanese officer with a katana did just that IRL.

Footage of the infamous 1995 San Diego tank rampage.

As you can see towards the end of the vid he gets the tank stuck on a concrete barrier, and them some cops get on the tank, open the hatch(which he didnt have locked for some reason) and waste him.

One man in a tank on a rampage is quite the menace, as even without ammunition they can crush cars as easily as an insect under someone's heel, as we see here demonstrated by a Leopard 2A4.

Can't court martial a corpse....

not likely since it was stolen from a national guard armoury, back then those places didnt even have fences round the vehicle park (some still dont have) 

you should see the gun run events if you want to see driver only devastation performed by a tank.... 

also ammo for the main gun wouldn't have actually done anything for him, he knocked the gun out of alignment the first time he whacked it... most folks dont realise this but modern tanks are a PITA in that regard, driving through objects can cause all kinds of problems to the primary weapon system....

when I was doing my driver/commander course wee had to wreck a bunch of vehicles and buildings without the main gun getting used and without falling below 60kmh whilst traversing through a built up area... needless to say the only gun you have available is the driver controlled coaxial chain gun and the commander operated externally mounted cupola machine gun...

you get 2k rounds for each gun and get docked points if you dont hit or crush every target inside the allotted time frame.... and you fail if you cause the main gun to become misaligned... not easy