Mortar Safety

[derf]

After watching the below video I was left wondering whether some mortar systems or rounds have some sort of safety feature in terms of arming after 1 second or two after being fired. Does anyone know?

http://www.liveleak.com/view?i=b7b_1207136461

[Corrupt]

Jeez
Well that round will be a tad off target...

[Kaapeli]

Well the fuzes we used had an acceleration safety. It's hard to explain without a picture but basicly the fuze has a couple of ball bearings that move back when the round has sufficient acceleration and this activates the fuse. So if the round doesn't leave the barrel with enough speed or is accidentally dropped it doesn't activate.
If this type of fuze safety was used in the clip you linked it was potentially very dangerous had the round struck something near the crew because it only prevents fuze activation if the round leaves the barrel too slow to reach a safe distance on normal elevations.

More modern electronical fuzes are likely to have time or distance fuze safeties.

[Firefly26]

In the M252 81mm, the rounds have a hole in the nose that air passes through spinning a kind of pinwheel if you will. After so many rotations, the round is armed. I think the 60mm's have the same thing. We were firing our 81s with the 60s from one of the line companies and they were trigger firing the rounds. They didn't have enough of us 11Cs to go around so the ammo bearers were usually 11Bs filling the slot. One of the ABs went to hang another round when the gunner hadn't fired the first one yet and when he did he hit the round that was in the ABs hand and both rounds went flying a few yards ahead, maybe less than 100m. I think the worst that happened was the AB got a finger severed from the fins, so they were both ok. There were no explosions and EOD arrived on the scene to detonate the UXOs. So yeah those rounds don't go off until they are far enough away which is a damn good thing.

[derf]

Thanks for that decent bit of info.

[Kaapeli]

One of the ABs went to hang another round when the gunner hadn't fired the first one yet and when he did he hit the round that was in the ABs hand and both rounds went flying a few yards ahead, maybe less than 100m.

These "double-loads" (barrel explosions due to two rounds being fired simultaniously and the ones you just described) are the most common and dangerous mortar accidents.
Over here several new safety devices and procedures are being considered because there have been so many serious accidents during the last few years.

The thing is that the fuze doesn't need to ignite in a situation like that for a catastrophic explosion. Even the explosives burning with the propellant powder will cause enough pressure in the mortar tube for it to shatter and injure the crew seriously or kill them.

[flanker7]

Double Loads are even more likely with trigger-fired mortars like the french MO-120RT. When the whole platoon is firing the crew may not realize that their mortar didn't fire(maybe the trigger string was not pulled hard enough) and load the next round.
I remember hearing of a similar accident in France when the whole crew got killed when the burrel burst

[The Evil Doctor Faustus]

brilliant!

double-feeds, not brilliant!