The base speed needed to double-jump as a marine should theoretically be given by sqrt((268-sv_gravity/framerate)^2 - 2*sv_gravity*18)

Since I'm too lazy to explain it again, quotes of myself:

A marine can bunnyhop on landing if the vertical component of his velocity is less than his base speed.

Hence the height difference h needed to bunnyhop at base speed v, jump speed* s, and sv_gravity g is given by:
h = (s^2 - v^2)/(2g)

And conversely, the base speed v needed to bunnyhop on a height difference h with jump speed* s and sv_gravity g is given by:
v = sqrt(s^2 - 2gh)

*see entry on jump speed below

(The height difference for going from ducking to standing is 18, half the difference between the height of the standing hull and that of the ducking hull. Also note that these formulae are based on an assumption of continuity and so are necessarily approximations in the discretized Halflifian mechanics.)

and,

Jump speed for every class is 268 units/second. However, HL seems to apply changes in velocity before changes in position, so one frame's worth of gravity is subtracted from the speed before you even leave the ground.

Therefore the correct formula for jump speed v is

v = 268 - sv_gravity/framerate

(These are from the first post of topic 97790 on the UWE forums; these forums won't let me post a link.)


Also, I tried and failed a long time ago to find a simple pattern in how weapons and ammunition affect run speed. The main problem is that adding or subtracting some weapon or bit of ammunition may change the speed or it may not, depending on what else you're carrying. You can't just say that adding a given item always subtracts a given number from the speed.