I noticed this also, at the airport in a TDM server I had an enemy unit about 50m infront of me, he was inside a hangar and I launched 2 or 3 40mm grenades at the ceiling above him causing no damage.

I then threw a single frag grenade which immediately killed him and also knocked down the entire hangar!

Those 40mm launchers are super weak

40mm grenades have a minimum arming distance, inside 50m would be considered danger close. 40mm frags simply won't go off if they are too close.

From what I have played it seems they have the same arming distance as ARMA 2 and expansions.

This is by design and is not a bug.

50m was an estimation, i cant remember the exact distance, likely closer to 80m though they were definitely arming and detonating.

It's not about explosive in close range guys, it's about simple physical damage.

Linkin is completely right, in real life grenades have a minimum arming distance, in fact the arming distance in arma 3 is actually less than it is in real life.

According to wikipedia:

http://en.wikipedia.org/wiki/United_States_40_mm_grenades

http://en.wikipedia.org/wiki/M203_grenade_launcher

Minimum arming distance appears to be about 40 metres.

However A3 uses some new fancy launcher, unsure as to if it uses the same ammunition as the m230 and m320 in A2. One would think so.

I think the OP is referring to the 230 g (.5 lb) projectile smacking into somebody at 76 m/s not even phasing them or blurring their screen (i.e. knocking the wind out of them, at the very least.) Granted, a plate carrier would stop this cold, it would definitely not be fun.

It should at least hurt a little, or knock you out if hit on the head.

Yup, me and a friend tried this. No effect on firing at point blank into the chest. Round would float in the air.

Hmm, that's not good. Even in ARMA2 if you were hit with one so close that it wouldn't explode, it would hurt you and throw your aim up into the air.

Few friends and myself have noticed this also. Does not seem right and believe this should be corrected. Not only should the person that is being shot at close range with the 40mm grenades feel the effect the one shooting should also feel this.

Hm, strange, because it says "hit = 40", "fuseDistance = 15". Based on that I'd expect it to kill someone, but you're right - it just stops and falls to the ground without harm.