I've already posted my argument on weapons of higher than 30 caliber and agree with you - the range on the Hotchkiss 1.65" gun should be 30" with its lower rate of fire (2). This falls in line better with the ranges of the Mk IV, especially the 7" version. In fact, there is a host of guns that are heavy caliber and have longer range with lower rates of fire. The two, three, and six pound British guns all fall into this category of weapon. They either have short 20" range with higher RoF or longer 30" range with low RoF.
I saw it as I noted above. And agree to it. Interesting point Mike; I'd been playing them like the machine guns as I think its more a function of the 7"/5" gun firing in the turret than what the other two positions have - they're not crewed if the main gun is firing. I always thought it was a bit artificial for them not to be able to fire if the main gun is firing. So here's a thought; no restriction on those two positions firing at all! And its the players option (required announcement pregame) whether they're MG or Hotchkiss. This makes the Mk IV beast even more imposing.
I would like an option rule that maybe that steam powered tanks cannot move in the second movement phase if a machine gun is fired. The guy tending the boiler or the steer man is manning the machine gun. OR a machine gun can be fired in lieu of one of the cannons for the MARK III.
Though you can take HMGs or Hotchkiss guns in Mk IV variants, apparently for the same cost, the Hotchkiss costs 15 pts. and the HMG 10 pts. in the Field Modifications section on page 85 of the rules. Given the lower rate of fire of the Hotchkiss and the higher cost that supports the 30" range argument.
Let's say you took a tank and built it with 3 Hotchkiss guns (2 in sponsons) - say used the Field Mods to replace the 3 HMGs in a Mk IImg interim tank. Now you have a tank with a 50% hit probability and 6 shots per turn if the target is a Defence 6 tripod in LOS of all 3 guns. That would give an average of 3 hits per turn. With +1 Power there's a 10% chance of a hit doing damage (needs to roll 10), so with 3 hits there is a 30% chance of doing damage each turn with 3 Hotchkiss guns.
Compare that with the 10% chance of doing damage per turn with a 4" gun, which has +2 Power (50% chance of a hit and 20% chance of that hit causing damage per turn - needs to roll 9 or 10). If the Hotchkiss gun has 30" range a tank with 3 of them is more effective than a plain MK II steamer if all 3 Hotchkiss guns can shoot.
The per turn hit and damage probabilities are better for the Mk IImg, though the range is only 20": with 3 HMGs with LOS it would average 4.5 hits per turn from 9 shots, and have the same chance of a damaging hit as the Hotchkiss with +1 Power. That would give an average 45% chance of a hit per turn, for only 5 more points than a basic Mk II tank with one 4" gun. (A MK IImg tank with field modification to replace the HMGs with Hotchkiss guns would cost 75 pts.)
I can see why the numbers of Interim Steamers with 3 HMGs and Infantry Support Steamers with 4 HMGs are limited by the rules - they're much more effective than the basic Mk II. With 30" range the Hotchkiss armed variant would match the per turn damage probability of a MK III steamer, but would cost the same (75 pts.).
I'm assembling a unit of 3 S2G 'Mk III Male' tanks with 3 guns - 2 in sponsons and 1 in the bow. The main guns are slightly shorter than the plastic AQ HMG and the gun barrel is a bit narrower so I can have them count as either HMGs or Hotchkiss guns. The tanks would be the gasoline powered equivalent of the Mk IImg Interim Steamer or of Mk IImg tanks field modified with Hotchkiss guns with 30" range and lower RoF. It'll be interesting to see how they work in a game.
As always an interesting discussion. I'm thinking on just keeping the Hotchkiss guns in the the Mk IV Monitor/Tank as is and claiming that the Hotchkiss are limited in number (now once you get to the French forces, this could be entirely different!) so as to be only used in the MkIV series alone. I've already noted that I'm using different arrangements for the S2G tanks as I've got them as much superior gunnery in almost all cases[Mars Pattern Gatling] (even the 4" is a better version per my notes on same). Loyalist alternative is very viable for his forces and I recommend folks trying both styles of the above weaponry for the excellent S2G tanks models mentioned.