Rod/wand/staff failure rates?

[Geofferic]

So my 28 Human Warrior picked up a rod of acid bolts but ... he cannot fire the thing.

Is there a way (spoiler?) to determine my failure rate and, if so, anyone know if I'll ever be able to use this or if I should just sell it?

Thanks!

[Big Al]

From the very end of http://www.juti.nl/hugo/Angband/Spoiler/ability.spo, your magic device use is 18 + 0.7*28 + int bonus = 37.6 + int bonus = ~42 (I'm just guessing a INT of 18/50 here)

Acid bolts rods are native to level 40, so ~42 - 40 = ~2

Chance of activation is 2 in 3*(4 - ~2) = 2 in ~6, AFAIK.

[Geofferic]

Ahhhh. Excellent.

Now I know why I'm failing. INT is 8. lol