The Artank concept is a good idea but as pointed out, adding a 155mm SPH turret to a MBT hull results in a very high and heavy vehicle. The 155mm Heavy Assault gun partially solves these problems, but this system is more a supplement to the conventional tank rather than an alternative.
Ralph Zumbro and myself have been discussing the requirements of forces optimized for Counter-insurgency, Brushfire wars, LIC and OOTW. Both of us agreed that maintenance, supply and logistical considerations should be simplified as much as possible. One way to do this was to replace the 105mm tank gun of the M8 AGS with a 105mm Howitzer such as the L13A1 used with the Abbot SPH and compatible with the L118/M119 Light Gun.
Such a move makes considerable sense. In fact 105mm howitzer-armed Shermans were used in both WW2 and Korea. The most likely targets for the M8 in the above roles are going to be enemy light infantry and buildings. Shells from a howitzer can deal with these just as effectively as those from a tank gun. The 105mm HESH round is very effective against the T72 or lesser vehicles- more on the topic of anti-tank rounds in a moment.
Some rounds in the 105mm family of ammunition are already suitable for direct fire, others need to be added.
The HESH (aka HEP) round is an effective anti-tank round, bunker buster and can be used as a general purpose HE round. HESH will probably prove to be one of the most useful and widely used rounds for the L13A1 equipped M8. HESH rounds are already available for the 105mm Howitzer.
Canister Anti-personnel rounds are also already available for the 105mm Howitzer. Two of these can take out an entire platoon in assault formation.
WP rounds have various applications in the direct fire role, including being used to mark targets for airstrike. WP howitzer rounds already exist.
No HEAT howitzer round currently exists in the US inventory, though other nations may field them. Such a round could easily be made by marrying a 105mm HEAT tank round to a howitzer casing. If this is done it would be a good idea to add the selective direct/proximity fuse that is used in the 120mm MP-AT round, giving an additional anti-helicopter potential.
An APFSDS round could also be created for the howitzer using tank round components. As well as anti-armour use the high velocity of the APFSDS makes it a useful anti-helicopter round. APFSDS and the training version of the round can also be used to destroy targets with less collateral damage. How useful an APFSDS rounds is at howitzer velocities needs to be determined in trials.
In Vietnam Ralph Zumbro replaced the shot in Korean war vintage Canister rounds with a plastic bag of grease. The resulting round turned the main gun into a very convincing flamethrower. Such "Dragonbreath" rounds should be officially manufactured. They might be even more effective with alternative types of POL or by the addition of powdered aluminum or magnesium.
A CS containing round designed for direct fire and close range applications would be very useful. One round bursting in a street, square or field would instantly make it uninhabitable to unprepared personnel.
More on Anti-tank rounds.
In Dick Hunnicutt's book "PATTON" he mentions the "SWIFTY" which was a 105mm version of the Shelleigh missile and could be fired from ANY 105mm bore, including the light howitzer. The Swifty seems to have never matured, but the Russians have barrel launched 100mm ATGWs for their tank and anti-tank guns. A 105mm version is not improbable.
Another idea not widely explored is that of rocket assistance. We all know that rocket assistance can increase the range of a round but little experimentation seems to have been done with using similar technology to boost the terminal velocity of a direct fire round. This is basically a higher velocity version of the launch mechanism of the RPG-7. A charge launches the projectile from the barrel and a rocket motor ignites some distance from the muzzle.
There is a third alternative for increasing the M8 Artank's anti-armour capabilities. Tanks such as the AMX-13 and Vickers MBT have been demonstrated with ATGWs mounted on their turrets. Similar mounts are also used on various IFVs. An M8 could mount TOW or Hellfire missiles for distant or heavily armoured targets. Externally mounting ATGWs allows systems to be easily upgraded or removed if not required. Mounting Hellfire offers some interesting possibilities. The vehicle would need a designating laser and this could also be used to guide in air-launched ordinance. Rounds fired from the tank could also be guided by infantry units.
Mounting Starstreak gives capability against both tanks and aircraft
An M8 equipped with a 105mm Howitzer can be used in much the same way as one armed with a 105mm tank gun but the howitzer offers several additional possibilities.
- Units within sight of an enemy will use the Howitzer for direct fire. However, nearby units not in line of sight can use their weapons to attack a discovered enemy by indirect fire. While the enemy may only be able to see one platoon of artanks he will in fact come under fire from at least company of vehicles.
- Lightly armoured, highly mobile units armed with ATGWs are very much in vogue in certain armies. Advocates of such forces point to the fact that the ATGW has greater range than a tank gun. A 105mm Artank can drop rounds onto any position within 15-17km. Lightly armoured tank hunter units will prove very vulnerable to HE or bomblet rounds.
- In LIC or OTW operations there is often a need to establish one or two gun firing positions. In non-linear operations it makes sense if the "guns" have adequate armour, secondary weapons and defensive systems.