A Possibly Nonsense But Playable Solution to The Crossbow Conundrum

So there's a problem with crossbows in GURPS. I go into it here. Essentially Rated ST has no limits, and nor does it change bow stats no matter how arbitrarily high it gets. This is despite the TL4 Steel Crossbows saying they exceed this nonexistent limit at the cost of halving ST for range and damage (which pretty clearly makes them useless).

The Solution

So in a discussion on the GURPS Discord with Max Wilson, he suggested something that I thought was almost there, but not quite, I thought about it, and came up with a solution.

The scaling rules on GURPS Low Companion 2: Weapons and Warriors pp. 20-21 say that a weapon with SM +1 has 1.5 × Min ST. This suggests the limit on bow Rated ST, before it needs to be a bigger bow is {Min ST × 1.5)-1, rounding up. 

Weapon	MinST	Max
Crossbow	7†	10
Gastraphetes	10†	14
Repeating Crossbow*	8†	11
Composite Crossbow	8†	11
Pistol Crossbow	7	10
Prodd	7†	10
Slurbow	9†	13

* Note that you still can only cycle a repeating crossbow of 70% of your ST (GURPS Low-Tech p. 74) 

Bigger  Bows

To exceed these limits just use the rules for SM +1 weapons with undersized grips using the scaling rules on GURPS Low Companion 2: Weapons and Warriors pp. 20-21. This allows bows of up to (2.5 × Min ST)-1 round up. Do not increase the damage bonus or weight per shot. Subtract 1 from bulk (so -6 becomes -7).

Even  Bigger Bows?

Crossbows larger than SM 1 are probably too large for SM 0 humans to shoot effectively without a rest or tripod, and beyond the scope of this article.

Steel Bows

Low Tech p. 74 says that the TL4 steel crossbows can be built at much higher Min ST, but also doesn't say what that means. Instead of using Min ST for figuring out the limits for these crossbows use the suggested ST in note [6] (but remember to halve effective Rated ST for damage and range!).

Weapon	Typical ST	Max	Max Effective
Fowling Crossbow	15†	22	11
Hunting Crossbow	20†	29	15
Military Crossbow	30†	44	22
Siege Crossbow	36M†	53	27

Garbage In Garbage Out

I obviously did zero original research here, and referenced no real world artifacts or data. These numbers are therefore not likely to match anything in reality. They are however both plausible and playbable.