375 grains is 0.0243 kg, and 450 fps is 137.16 m/s, for around 230 J. At the cinematic scale, that's 8.64 damage, or 2d+1. At the realistic scale, that's 6 damage, or 2d-1. Using the range equation from
The Deadly Spring (which is also where the damage is calculated from), we get a maximum range of 1460 yards. Typical modern arrows are apparently between 9/32 and 5/16 inches in diameter, for a 1/2D of between 400 and 500 yards. They fail to note what sort of crossbow they're basing things off of, but I'd assume one that just uses arm strength alone. They
may have left off the time to draw and place the arrow (one second, negated with Fast Draw), but either way the quoted reload rate implies about a 2 second reload, as you note. The weapon's total length is essentially the same as an M4, so Bulk -4, as you note. 2" groups at 50 yards implies a maximum skill of 26 or 27, for Acc 3. Overall, something like this:
Code:
TL Weapon Damage Acc Range Weight RoF Shots ST Bulk Cost
8 Airbow 2d-1 imp 3 450/1450 7 1 1(2) 8† -4 $700
I left off LC as I wasn't certain. Cost was based on what current $999 would cost in 2000 (which I think is what GURPS dollars are roughly equivalent to), and I went with higher MinST than you because I felt comfortably using the weapon should require it to fall within 1/2 BL (rather than falling within BL, as you opted for). The above are meant to be realistic statistics - in a cinematic game, 2d+1 imp for damage and Acc 5 are probably appropriate (bows in general have higher damage and accuracy in cinematic games). In fact, the weapon's actual Acc may only be 2, with Fine (Balanced) arrows being used by default. Using broadheads would probably mess with damage and range a bit (I think the quoted statistics are for the field tips; see
The Deadly Spring to figure out what replacing that with a broadhead would do).