hello all,

i have a question about horde vs horde combat. how many  attacks does each horde get, i know about  stardard attack and swift….. but a horde attacks everyone it can, if we use hordes as single targets then horde vs Horde is going to be exceptionally slow and boring as. 

so im wondering what other people do in this situation ???

I believe the standard option is "They negate eachother; what's left +/- the party is what gets dealt with".

Four PCs and a 150mag horde vs a 200mag horde becomes 4 PCs vs a 50mag horde.

Four PCs and a 200mag horde vs a 150mag horde becomes a bloody massacre.

The faster and better the PCs do, the better 'their' horde does.

but what if the pc's are not in the fight for some reason, or they leave mid fight leaving there hoardes to fight it out

Just use the normal Damage rules as if the other horde was an individual rather than a Horde. i.e. no size modifier and +1d10 damage per 10 full magnitude up to +2d10 max. That way, you can fight out the battle with a clearer winner/loser and a solid indicator of the winner's losses and the length of time the scrap took..

so deal damage straight to the mag of the horde ??

Yeah, pretty much treat the Hordes as a pair of bruisers slugging it out (range or melee as appropriate to the set up). Naturally , a Mag 30 Horde of Orks has quite an advantage over the same size horde of human-types, as it usually should, but the point is that the battle is over with quickly and fairly simply.