Are they reproducable by the design system though - if not either the design system is broken or the stock numbers are...
If design sequence 7 can come up with the stock numbers in the weapon tables then all is well. I've never actually tried this out...
Yes they are, for certain values of Yes. The guns all have the same range as quoted in Book 4, although I don't think the weights and prices line up exactly.
Mercenary also doesn't make any representations as to the power plants needed to power the weapons.
There are a few minor niggles with the designs. For example, the 'B' gun sits just below the threshold where it gets a burst at extreme range, which seems a bit silly from a utility perspective. I also think that the inverse square law of range makes the A-gun rather smaller than one would expect to put on a grav tank, so some of the tech as described in Mercenary doesn't make a lot of sense mechanically if you try to implement it in Striker.
If you diddle the power plant scale efficiencies a bit then you can make sensible TL11 grav tanks with a B-gun that makes sense (around 17MW) and a level of armour commensurate with energy weapons in this power range. The tanks will weigh in at about 70-100t. You can do something similar at TL10 by making the A-gun a bit larger, somewhere in the 10-15MW range. It still has no burst at extreme range, and long will be about 3-3.5km. This is longer than the canonical A-gun, but it works if you hold your head just right and think of it in terms of a first-generation grav tank.
I used to hand-wave this a bit and view self-propelled A-guns as something like a close support weapon rather than a tank. I would build a design that had enough power to power the gun or fly but not both (also somewhat canonical). However, as the gun is only useful out to Long range (2.5km) the vehicles had to be small and cheap to be worthwhile, hence the self-propelled gun designs coming in a bit over Cr1m.
Unfortunately the RAW scale efficiencies have a gap in the range where a B-gun armed grav tank would be a sensible scale, making the smallest sensible grav tanks a bit bigger than this and needing a 10m
3 power plant to make a break point. You can design a 27MW power plant (weighing 36t) or a 40MW power plant (weighing 40t) but nothing in between. Building off a 40MW plant will wind you up with a tank in the 120-150t range mounting a 20-25MW gun; you can also do this at TL10. This still works for a skirmish but it doesn't quite line up with the descriptions in Book 4. There is a similar disconnect with the X and Y guns at TL12-13.
Unfortunately, if you take the power plant up to 14M
3 then you get double the power for not much more cost and you're into the leviathans that are pretty much invulnerable to anything else on the battle field, and thus kinda boring. This is more of an issue if you're doing TCS style Striker where the players design all their kit as well as put it into battle.
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I may have spent far too much time playing with and houseruling Striker in my mis-spent youth.