is this suitable for use as shooting line on speargun?
Most defintely, excellent for rigging multiple shafts (1 shaft with 1 wrap for reef hunting and another shaft with 2 wraps for more reach). Can also take Knots when in a jam.
That's what I use it for then have it crimped to dyneema line on my reel
Yes, provided it's for a setup using wrapped line (as opposed to a reel). It's strong and resists nicking, it does great as shooting line. You will need a crimping tool and crimps
I'm guessing u are using a reel , in that case, NO, monofilament is used to connect your shooting line( I recommend using Omer too) to the shaft , if my answer wasn't clear enough check ( how to rig a speargun ) on YouTube , hope that helps