Ships & Modules

Switch ammo depending on range of rats, carry both with you. Keep in mind Barrage does mostly explosive damage so is fairly bad against certain rats and you'd want a t1 ammo anyways. Switch the ammo type depending on rat resists and range (like phased plasma vs serpentis, emp vs blood raiders, fusion/barrage vs angel cartel etc.

With the falloff the Vargur has you will still be doing massive damage with short range ammo at conciderable distance. I don't remember how it compares to the Mach falloff wise but you can use T1 short range ammo effectively out to some 70km on it.

I'm also wondering how you're going to keep from capping out in certain situations, with the dps it has you won't have to run your tank for long periods most of the time, but if you warp right into 10 BS like in say worlds collide you will have to run it for a decent period flat out in which case without a cap booster as you have now you will most likely cap out.

EFT gives you the answers you're looking for.

Up to 30km T1 (non-faction) ammo wins and after that Barrage takes the lead but up to about 50km the dps difference isn't big enough to warrant the extra ammo cost. Also note that Barrage is Expl/Kin so would you fight non-minnie based NPCs then barrage becomes less logical to use, even at greater ranges.

based on math. i assume you have different fit

Projectile ammunition range bonuses and penalties are only applied to the optimal ranges. With autocannons, optimals are vanishingly low (3km difference between short-range and mid-range, as you've stated), so you only start to see major range differences when you deal with T2 ammunition, which has bonuses (for Barrage) and penalties (for Hail) to the falloff.

Incidentally, that's probably why you often see autocannon ships using Tracking Enhancers; the 30% falloff bonus dwarfs what any other module or rig will give (aside from a Tracking Computer with an Optimal Range script).

I hate using any mission ship w/o a propulsion mod (an AB fits with a pg implant, or a small bit of faction - RF XL Booster instead of t2). I have long used the thumbrule: effective projectile range = optimal + 1/2 falloff.

Thus you'll be doing most of your DPS up to about 40k range (I get 72 falloff so 4.2 + 36 = 40k), however for frigate targets, feel free to engage @ optimal + falloff. So, t1 ammo is fine for missions if you can keep NPC's within 40k.

With the marauder role bonus, you're only using half as much ammo as you otherwise would. Still more than an arty Mael, but not obscenely so. Personal preference though, I guess.

(Edit: It also pushes the point at which Barrage takes over as the best damage from around 30k to out past 40k)

I've run L4's in both a Mach and a Varg and never bothered once with barrage. Being an EXP ammo the only time to use it would be against Angels who will burn in to close range making the falloff bonus to the ammo redundant.