I'm not really good with fixed weapons, but from what I learned, the best advice is: Just do it. I still have never used fixed lasers or MCs, I'm just to lazy for that

. But when I decided to give PAs and railguns a try, I engineered me a set of plasma slug units and fitted an extra fuel tank, so I would not run out of ammo; efficient for the PAs and long range for the railguns. With those, I just went to a HazRes or compromised nav beacon and went to town. Going to RES sites with cops turned out to be counter productive because they would kill the prey before I could line up my first shots.
I'd imagine you would need a sturdy ship though, because you might need to tank quite few hits in the beginning - I was a bit overwhelmed with aiming and evading at the same time at first. Also don't take on wings, even if they were a piece of cake with gimballed guns

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Another thing: Don't mix different projectile weapons on one fire group; the different reticles can get very confusing. If I mix at all, I stay with one kind of projectile and one kind of hitscan weapon.
Try the plasma slug experimental. Great for training, because missing doesn't waste what little ammo you have. Just watch your fuel level

. I actually liked it so much, my bounty hunting Krait is fitted with five efficient plasma slug PAs and an extra class 5 fuel tank, and it is so much fun, plus you can stay in a HazRes forever. Smaller pirates like eagles explore in one volley - you could call it NPC ganking

. They are not as efficient as the laser/MC combination for me, but the fun factor is much bigger.