Gun Construction Kit or similar resources?

[Polydamas]

Originally Posted by Varyon

Vehicles was for 3e but works fairly well. Note that most firearms tend to be "low powered" or "very low powered" in that system. Acc and MinST have to be converted (for Acc, just halve it; for MinST, just adjust for scale - in 3e, ST was linear, but in 4e, it's quadratic), and you'll need to come up with Bulk and Rcl based on similar weapons.

S. John Ross has also had a bare minimum list of generic firearms for modern action games on his website since the middle 1990s (Edit: link). High Tech is also very easy to adapt that way, since the list of guns in that book and appropriate for any one place and time is not vast. If you want to pick one revolver, one automatic, one bolt-action rifle, one semi-automatic rifle, and one shotgun then declare "these are the only weapons available in my game," one can do that in 10 minutes.

I don't think that it is reasonable to expect a design system to both allow arbitrary simplicity and to give plausible results for any imaginable weapon quickly.