It all depends on what they're using. I won't even attempt attacking a chaingun BS, their constant damage on your large hitbox will be the end of you. Flamers are easy, just feint your pounces until he gets low on ammo, and put in some real ones if he gets stingy with the flames. Pulse is easy enough to approach in an open area, but is dangerous up close and in hallways. Luci, imo, really isn't a problem if you hit-and-run. The only time you'll die vs a luci, 1on1, is when you're staying too close to the BS, since luci shots are hilariously easy to dodge, or when you're in a tight space.
When confronting heavy weaponry like that, I find what works for me is to gain ground with a pounce that's deep and aimed at one side, then follow up with a smaller pounce or a chomp, then escape and repeat. Doing so, you gain ground without leaping directly into their projectiles, and you gain a moment to attack as they turn around to face you.
Also, another thing to do is feint your pounce destination. Look to one direction as you charge up your pounce, then quickly spin to the other side and pounce that way. It throws off prifles and lucis trying to lead you.
The most important thing is never to stay close to them, that's a habit I'm still having to correct myself of. Chainguns, prifles, lucis, and flamers all do far more damage than your chomps vs a BS. If you're close to them, they get every single shot in, and you can never hope to match that with a chomp. Your only advantage is when you're sailing across the room, dodging 90% of their fire.
