I feel like I should know this...

[jets]

Blocked FG and/or Punt behind the line of scrimmage (4th down)...live ball. Defense picks it up and attempts return - makes it about 10 yards and fumbles, original offense recovers. 

1st and 10 for the original offense? (The team attempting FG/Punt)

And then...does this enforcement change if it was 3rd down? 

[miner_35]

27 minutes ago, jets said:

Blocked FG and/or Punt behind the line of scrimmage (4th down)...live ball. Defense picks it up and attempts return - makes it about 10 yards and fumbles, original offense recovers. 

1st and 10 for the original offense? (The team attempting FG/Punt)

And then...does this enforcement change if it was 3rd down? 

This is multiple possession changes and will be a first down for whichever team ends up with the ball after B's fumble in either scenario as long as B had  clear possession prior to their "fumble".

[gopher2]

Yep, first down for whoever ends up with it.  We blocked a punt years ago and slow DL tried to scoop and score except he got hawked and punting team recovered for a 30 yard loss and they got the first down.

And it doesn't matter what down it was if there was a change of possession.