Kroom The issue is that with the factory the same size as the only storage there's no point in having ammo transfer.
A half storage would presumably hold 16 shots, which isn't very much for the cannons, but could be enough for the mass driver if it didn't use as much ammo per shot as a railgun that does more than three times as much damage.
Going over the numbers the Mass Driver does not appear that it would be in danger of being overpowered if it was more ammo efficient. The Plasma Lance puts out 1333 dps at 150m using 6 tiles. The Fusion Cannon puts out 2000 dps (1000 vs shields) at 150m using 3 tiles with boosters one tile long adding +100% damage. The Mass Driver puts out 1000 dps at 100m using 4 tiles with boosters occupying 2 tiles and adding only 15% damage and 15m range. An 8 tile long Mass Driver still doesn't quite match the damage of a Plasma Lance and lags noticably in range and unless there's an unlisted penetration boost has less penetration. A fighter that fits on a pad can only have 10 tiles of railgun for 1450 dps at 145m, which with the lesser penetration depth is still not clearly better than a plasma lance.
An ammo storage or factory is the same size as Walt's small reactor, which will comfortably serve two plasma lances or any combination of up to six fusion loaders and fusion boosters. A 10 tile mass driver and factory come to 16 kilocreds, while two plasma lances and a 2x2 reactor come to 25 kilocreds, but do pretty near twice the damage at a slightly longer range with a bit of power left over. An 8 tile 5 booster fusion cannon and reactor cost 30 kilocreds for a bit over four times the damage against shields and better than eight times the damage against shields and doesn't need a crewman. If the mass driver only used 1 or 2 ammo and there was a 1x2 16 bullet storage they would still be the weakest and least efficient modular weapon in the mod, but at least they would be able to fit in spaces the wrong shape for a fusion cannon and 2x2 reactor.
One quality of life issue for the next release is that the point defense capable guns in the mod don't have the mode options Walt's point defense does and I didn't see anyone else mention it in this thread going back to the last release announce..
