>>64063274
I mean, helical magazines sit in a similar position to a folded one
But as for keeping the rounds with the nose towards the gun and somehow getting them in - the Czechoslovak ZB-47 does something like that, although the magazine isn't perfectly horizontal, it's at a bit of an angle. There's a wheel of sorts that the bolt pushes as it cycles, which rotates the top round in the magazine to the appropriate position for the bolt to then pick it up

https://www.youtube.com/watch?v=TYVSe6s8kGE