As a quick bit of advice for those of us who would like to use automatic weapons in a precision weapon dominated mode, this might be a bit of help.
Basically, you need to play extremely aggressively, use thrust to your advantage, and get up close. You don’t want the BR player to be able to line up that 4 shot. If you can boost or jump boost near the enemy, all while spraying and hitting nearly every shot, you’ll be able to get the kill almost every time.
You do need to be careful about getting 2v1’d, which happens a lot in team BRs. In that case, it’s best to retreat or pull out your BR and try to fight back as best you can.
Hopefully, they put in AR/magnum slayer into the full release in its own playlist, but until then: good luck!