Thanks for moving the thread. I hope that you get good feedback.

I'm not sure what you're saying about Grey Owlite Shield's status protections. Like any shield, it blocks all attacks from the user until it breaks. Because it has fire and shock protection, it will take longer to break under fire and shock attack, than a shield without such protection would. If you don't already know all this stuff, then try the wiki article "Shield" and the Shieldbearer Guide.

2 mediums = very high /= high
The ironmight shield is better than the aegis since it has more normal and one status resist while giving the same amount of pierce protection.

I notice on the armor you said both pieces make high bonuses, when it's actually very high (I think it's what you meant judging by what you said on swiftstrike, just pointing it out before the inevitable).

I notice on your preferred you have both nameless and swiftstrike. In my opinion you should use one or the other, mainly due to the fact that some of that speed bonus will go to waste and your shooting will already be very fast. It would make more sense to invest in a 5* shield or use shadowsun + swiftstrike, which is VH damage and High speed without trinkets/UVs.

As for the shields, I would not recommend Aegis, mainly because almost all piercing attacks are very easy do dodge and predict. As a gunner, you will rarely be touched by piercing attacks so why try to build defense against it? I would invest in a shield that resists the damage type that hits you the most, unless your doing something like a shadow lair. Swiftstrike is nice, but I would also get a 5* shield for areas that have mobs who will one shot your swiftstrike.

For elemental guns, have you considered the elemental alchemers? As of late I've been finding myself using them over the AP, mainly because of the status effects and their powerful charge shots. Keep in mind the alchemer's shots can hit a target more than once doubling it's damage output and the charge shot can outright kill things, you just gotta aim it right. Polaris is nice, but its not so party friendly because it fills the screen with turquoise blasts and if used wrong you'll end up with much less DPS than the other elemental guns.

Sentenza, in my opinion, seems to be the best all around shadow gun, unless you get an umbra driver with damage vs gremlin medium on it. Again, it's like the elemental alchemers here: Aim it right and it will destroy things. However, Sentenza can hit past gremlin's shields if aimed right which helps a lot on them. The Biohazard line is a lot of fun to use too, though it has some issues than need fixing, which is probably being worked on as we speak with that weapon balancing.

As for pierce guns, I'd highly recommend getting a callahan before getting a blitz needle, unless your gonna bring your Polaris to every fiend stratum you see. Devilites will laugh at your blitz needle attacks and troll you to no end. Polaris works well on them for some odd reason, but the callahan will kill them faster. Blitz is nice for vana if someone is shivering him, otherwise callahan is better cause it does not leave you immobilized as long. It also works very well with large amounts of attack speed to boot. Another plus for callahan is that it will interrupt gremlins, meaning you can lock down a gremlin healer with it. Blitz seems to work better for wolvers once you get good at it though, and it can kill a trolljan in one charge.

The above is my opinion though, take it as you wish. I'd try out different weapons and see which ones you like best.

EDIT: I was ninja posted. I'd highly recommend Valiance for that 4th weapon slot if you wan pure gunning. Otherwise one of the toothpicks would be a great choice for dealing with gunner's worst enemies: The Fiends.

Here's what I roll with, take from it what you will.

Armors:
-Perfect Mask of Seerus (UVs: Normal Medium, Elemental Low)
-Justifier Jacket (UVs: Shock Maximum)
-Swiftstrike Buckler (UVs: Elemental Maximum)
-Elite Trueshot Module x2 (Damage Bonus Very High collectively)

Weaponry:
-Argent Peacemaker (UVs: CTR Medium) / Nova Driver (UVs: ASI Low, CTR Medium) / Hail Driver (UVs: CTR Medium)
-Sentenza (UVs: CTR High) / Umbra Driver (UVs: CTR Medium)
-Blitz Needle (UVs: CTR Medium)
-Dread Venom Striker (UVs: ASI Medium) / Venom Veiler (UVs: CTR Medium) / Voltaic Tempest (UVs: CTR High)

Overall Armor Bonuses:
-ASI Maximum
-CTR Medium
-Damage Bonus Very High

What this means:

This gunslinger set is nearly unrivaled in PvE, for soloing, PUGs, whatever you need. Nearly every gun in my arsenal receives a CTR Max bonus at Level 10, and even if having a Shadowsun set would be better for T3, most things that deal shadow damage are interrupted by a shot from the Argent Peacemaker. With everything fully heated, most guns get an ASI Maximum / CTR Maximum / Damage Bonus VH bonus with this set, as long as it has at least a CTR Medium UV. Essentially, there's endless possibilities with this set without having to spend an exorbitant amount of CE/crowns on getting the stuff with VH UVs. I chose to put CTR UVs over on my AP/Sentenza to round off their capabilities with this armor set in mind, as well as to maximize how much I was getting out of my armor set.

You can easily swap out the Justifier Jacket for a Shadowsun Slicker if you would prefer to have Shadow defense in lieu of piercing defense, and benefit from a higher damage bonus with a dropped ASI bonus. Or you can compensate for that by getting an ASI trinket for guns in exchange for a damage bonus trinket. Really, the possibilities are pretty expansive with this set and can be altered to fit the situation. This is just what I'm typically seen using nowadays though, since I don't find shadow damage to be a threat half of the time.

EDIT: Those who said that fiends will laugh at your blitz needle must not use the charge attack very often, as it more often than not will drop a small group of fiends. While it does leave you vulnerable to attack, it also forces you to time your charge shots better, which is beneficial all around. If that doesn't work however, just stick to an alchemer until you get the hang of it. Even if they dodge, the ricochets will usually chip some damage into them anyway.

Damage is almost always better than asi. If you have one suit of armor, get shadowsun. Or shadowsun/mask of seerus.

If you have one shield, get crest or skelly. If you have two, get owlite.

The antigua line is not more mobile. You have to shoot more, which slows you down, you just dont have to reload as often. Try pausing before shooting the last bullet in the clip if you need mobility( alchemers are the best at this).

Polaris is good for a few things: easily destroying towers, spamming groups of devilites, and in conjunction with electron vortex. Otherwise, alchemers generally out dps polaris and are not nearly as irritating for party members.

If you have one piercing gun, get blitz. They are both useful, but fsc is the main source of income. I would really get both though.

I use nova driver/ umbra driver/ callahan/ blitz as my default loadout. Umbra gets switched for polaris in devilite levels, and blitz gets switched for sentenza in gremlin levels.

I usually only use swiftstrike at fsc and rjp. Otherwise I use crest/jelly/owlite.

"Normal and Elemental defense. (In PvP: defense against the "popular" Divine Avenger, and most Alchemer guns. -|- In PvE: Unknown)"

"In PvE: Unknown"?? There are ele strata in every tier (of course, in T1 they don't actually deal ele). Nothing unknown about it.

Also, Vana's bullets deal ele.

"3 Bars of freeze defense. (takes some time off of the duration, but not needed if you have a good team that will get you out of it)"

Freeze is more or less useless, since the next hit on your shield will break it.

"Normal and Shadow defense. (In PvP: defense against the Gran Faust, and the popular Senteza. -|- In PvE: I've heard Shadow damage is common in T3)"

All damage types are "common in T3", generally.

You may be thinking of FSC in particular, which is almost all undead/fiend. That's valid, but a gunner really should not be getting hit by zombies a whole lot. I would mix PMoS with the Shadowsun Slicker instead. One piece of shadow def is sufficient, and PMoS gives you all you need: a bit of ASI, CTR Med for your Blitz, ele def for Vana's bullets, fire for shadow fire etc.