Cannon rounds
 

I have noticed my cannon rounds from my 109 exploding in the distance after I fire them off. Almost like they are hitting a wall. I did'nt know that cannon shells did that unless they were fitted with a proximity fuse. Is this working as intended or a bug?

It's correct, the cannon rounds had self distruct mechanisms built in.

Yes it's true :)

I read somewhere that it's to avoid the cannon rounds potentially hitting something else and exploding. If you're in a tense dogfight over berlin you wouldn't really want the 20mm rounds to explode when impacting german houses would you?

On another note later ammunition types are proximity fuzed being able to detect targets by miniature radars.

Americans started using radar detonated artillery rounds during the later parts of the war I believe against the germans. Instead of digging into the ground before exploding, the proximity radar in the nose of each shell would go off at a given height above ground (say 1-2 meters) effectively barraging the area with shrapnel, where the older rounds would leave probably 50% of the shrapnel under ground.

American Prox. fuses were only for large artillery and naval guns, and came in the late stages of the war, especially in the ETO.

Well, I guess you learn something new everyday. Thanks for the info guys, it sure clears up that little mystery.

The German shells were set to go off when they stopped rotating, either by hitting the target or just by flying out far enough...

Frey is partially correct.. The shells had a simple device that when the shell was spinning fast the centripetal force kept the contacts apart..once the spinning slows the lower force would allow the contacts to meet and boom.. self destruct..

Did it really occur so close to the firing aircraft?

2-4 seconds after firing. Depending on a few variables.

...seriously? Radars in shells? Uhmmmm, I have a fair knowledge of ammunition and ww2, but I swear I never heard of it, it is also true you learn something you everyday.. Do you have any reference on this?

AFAIK Proximity fuzes were normally magnetic. As for the rest fuzes could be time set and/or altitude set.