The FV4005 Stage II has been nerfed several times. It seems that people apparently don't like getting 1-shot, and because of the popularity of the FV, something had to change. On the 1.5 update, the following changes were made:
Accuracy: 0.38 –> 0.42
Top Speed: 35 –> 32
Reverse Speed: 12 –> 8
The issue with these nerfs is that, rather than attempting to solve the problem, they just try to make the tank more annoying to play. Additionally, due to Equipment 2.0, these changes can be negated: On an F2P account, with no food or special vents or whatever, the Aiming Unit/Ventilation/Turbocharger build with a BIA crew and vent purge gets the accuracy down to 0.35.
Rather than making the tank annoying to play, it should be that more options for playing the tank are made more viable. So we should look at the most similar gun in the game to see what the differences are: the 17 cm Pak on the Jpz E-100. Although the 17 cm AP round does 100 less damage, the Jpz has a slight DPM advantage because of its reload. It also has the accuracy to pen an AP shell. This makes AP a viable option on the Jpz. Thus, on the FV, the AP shell should also be made into a more viable option, and the HESH shell into a less viable option:
Increase the damage of the 182.9 mm AP mk. 1 shell from 1150 to 1200 and increase its penetration from 310 to 320.
This puts the DPM with AP on par with the Jpz. It also makes AP more viable in absence of a high-penetration premium round.
Decrease the penetration of 189.2 mm HESH mk. 1 shell from 230 mm to 185 mm.
The 189.2 mm HESH mk. 1 shell originally entered the game with 285 mm of penetration, and was subsequently nerfed. This needs to happen again. 185 is a good value, because it still provides the opportunity to penetrate some shots, but prevents things like frontal penetrations on heavy tanks and such. This makes the HESH shell less viable and would encourage players to consider the AP shell.
However, the previous statistics of the gun must be returned. No one is going to try to fire an AP shell with 0.42 accuracy and miss when they could fire HESH and splash. The dispersion on traverse could also be improved slightly, maybe from 0.32 to 0.27.
There is one other change that I would suggest. Looking at the line, especially the FV4004 Conway, there are two guns: A derpy low DPM gun with nice HESH and a competitive high-dpm gun. The other tank with an L4 gun was removed because it didn't fit the line [FV215b 183], so the FV4005 should also fit its line. A second gun option should be added:
[this is not a gun that was historically mounted on the FV4005, but this gun could provide a competitive alternative to the L4]
Ordnance BL 6-inch cwt. Howitzer
Calibre: 6 in/152.4 mm
Shell types: AP/AP/HE (Common Pointed 100lb Shell mk. XIIA/B, High Explosive 100lb Shell mk. XVI)
Penetration: 295/370/90 mm
Velocity: 960/960/830 m/s
Reload time: 15 s
Rate of fire: 4 rnd/min
Base DPM: 2600
Aim time: 2.1 s
Dispersion: 0.32 m
Dispersion (mov/tanktrav/turrettrav): 0.29/0.30/0.12
Dispersion (firing/damaged): 4/2
Module damage: 203
Ammo capacity: 35
Gun traverse: 23.63°/sec
Gun traverse range: 180/180°
Turret traverse: 14°/sec
Also, decrease the view range from 390 to 380 m.
This gun would provide a non-derpy alternative more in line with other tank destroyers. With an accurate 650 alpha gun, it does remain somewhat unique. This gun, similarly to the Conway, allows full turret rotation, but also increases the elevation from the horrendous 8 degrees to 14 (not much, but vast improvement). For someone looking to continue on from very nice 120mm on the Conway, this provides a good option.