What Bopp said was my first thought, too: the most likely reason to mix Jelly guns (Sentenza and Argent Peacemaker) and Alchemers/Drivers is to quickly clear blocks while enjoying the DPS and burst power of an Alchemer.

I get an impression that gunners favour Alchemers over Jelly guns for both Elemental and Shadow because they offer better DPS and, as Bopp mentioned, enough burst damage to ninja-kill monsters without having to deal with retalliation/healing/whatever. For similar reasons, Needlers are preferred over Magnus for Pierce. I can vouch for this, now that I've tried all 4 of those weapon types at 4-star; my Alchemer and Autoguns are very satisfyingly powerful, while my Black Hawk and Mega Magnus feel anaemic. IMO swords look appealing until 3-star for Pierce, where Needle Shot becomes available, and 4-star for Elemental and Shadow, where Alchemers mature into wonderful killamajigs. I love my heavy Sword, but for practical purposes I'm more comfortable with a Blaster's greater agility than a sword's greater knockback.

I'm told that the Jelly guns and Magnus are mostly favoured for being easier to use and offering some nice convenience features; Jelly guns for being so handy for switches, blocks, and sometimes attacking when no other weapon would let you get away with it, and Magnus for completely shutting down some monsters and/or letting you hit them with something bigger, including Gremlin Menders. My experience doesn't agree so well, though. I find the projectiles apparently failing to damage anything; I dunno how this buggy behaviour works, but it seems to not affect every one so it's still a good idea to try one out and see.

Since you're going all out with 4 weapon slots and focusing on guns, I think you're most likely to favour Alchemers for Shadow and Elemental, and Blitz for Pierce. I've less impression as to what's most likely to be your favourite fourth gun, but Supernova (if that's the Normal one) is probably the most popular since it's good at sweeping big mobs into corners, followed by Valiance for enforcing personal space or Argent Peacemaker for what swordies use it for, though I'd rather use an Autogun for hitspamming blocks and ore deposits since it pulls its weight in a fight much better. I do think the Catalysers are very underrated, though, so I recommend trying one since "Built to Destroy" is not terrible in payout even without the tokens. The Cats' explosive power is much more useful for mob DPS than the Pulsars' explosions, and Catalysers are very versatile when you get familiar with the timing, orbits, and how long the explosion interrupts monsters' animations for. I see it as a somewhat less defensive and much more offensive alternative to the Pulseguns.

Pepperbox is also nice, but not for every one; play around with your Autogun before upgrading to Needle Shot and, if you find yourself missing the Autogun's mechanics, consider following the Pepperbox path as well. Since Blitz is considered an essential weapon for a gunner to know how to use, learning to use Pepperbox shouldn't be much extra trouble since a lot of mechanics are shared. If you were going for CTR max and then whatever ASI you can get I'd strongly suggest looking into Pepper, but since you're not going for Chaos' bonuses this might possibly feel a bit underpowered.

FWIW, if I were going for 4 weapon slots I'd definitely go for the Blitz Needle, Biohazard and either Storm or Nova Driver for type coverage, and mostly equip two of those at a time based on stratum. The other two slots would usually be filled with Blaster for reliable fallback if things get uncomfortable, and either a Neutraliser or Volcanic Pepperbox based on which abNormal-damage weapons I have equipped. That way, I could almost always have a Blaster, Alchemer, Autogun and Catalyser of some sort since I just adore all 4 of those types. YMMV. To focus on just one set of four in order to get up faster, I'd go for Bio, Blitz, Blaster and some Elemental Alchemer, probably Prisma Driver. (I haven't decided which of those two Alchemers I like more, but if I had only one Elemental weapon I'd prefer it not have Shock on it, and hypothetically if I had more than 2 weapon slots I'd consider Cryotech path or any other Freeze weapon, since having a Catalyser, Autogun and third weapon slot is begging for Freeze to be added.)

Edit: Autoaim on by default is a pain in the neck, IMO. It very often chooses targets other than the ones I want to attack, and for me at least Alchemers aren't even the only weapons whose optimal placement is rarely where autotarget aims, even when it's picking the correct target. I use Catalysers a lot, which have slow enough projectiles that I have to lead at longer ranges. I use Blaster a lot, especially for triggering blast blocks at the exact time I want, when there are lots of monsters nearby. I do find it handy for attacking Southward and occasionally for placing autogun attacks, and I have a key bound for those moments.

You gonna have a hard time vs devilites and wolvers with no callahan

My machine can't handle most places with gobs and gobs of fire, so I'm an eternal newb in FSC, the Gauntlet, (Fire room) Compound 42, etc. :(

First, I do recommend getting at least the 3-star Antigua and 2-star Pulsar, but not by buying with crowns or energy, because to do so you'd be spending many times what you have to for it and the process of earning them is good practice for wisely choosing your upgrade paths. In my opinion, the best way for a gun specialist to start out is by earning Antigua and Pulsar by collecting tokens, while spending some small portion of the crowns you get along the way to buy Voltech Mk II or Prismatech Mk II and either buy or craft the 2-star Autogun. IMO the best guns for earning your first Pulsar and Antigua are the Blaster, Autogun (as long as it's not upgraded to Needle Shot yet) and any Elemental Alchemer Mk II. As soon as you feel comfortable with at least two of those weapons, or right away if you're comfortable with your free 2-star swords, start earning your Pulsar even if you don't have your Antigua yet. (Pulsar is great for newbies soloing the mission used to earn Antigua, but Antigua's not particularly useful for earning any other guns.) After you have those basic gun types, just keep using and enjoying them in T2 until you have a really solid feel for which upgrade paths feel right for you. That experience will give you a much more solid, reliable idea of what's best _for you_ than any advice given by a stranger; we can give you tomes' worth of observations, but you could always belong to a significant minority that just can't get any enjoyment out of some standard bread-and-butter guns and/or just takes a shining to an unpopular one like Catalyser or Pepperbox.

That said, one of the observations I've made is that Pulsar (of either damage type, it doesn't matter) is by far the most easy-to-use and safe way to deal with Rocket Puppies when you get to T3 and at least one of the safest AND quickest ways to shoot down big walls of many turrets.

For safety everywhere else, Blaster is the best bet. The knockback is enough to be useful but not enough to be dangerous in a party, and lacks the Pulsar's minimum range, yet it doesn't seem to sacrifice anything for that nice defensive feature; mobility and DPS are comparable to Antigua, yet range is better and more reliable, the projectiles have top-notch speed like Magnus so you can reliably hit, and it even seems to have higher-than-average flinch power. It's definitely worthy of being billed as the Spiral Order's standard sidearm, IMO.

P.S. Despite what Trouper said, I bring my Master Blaster when I expect Devilites, not my Mega Magnus. If I expect a hard fight, I'm likely to also use Radiant Pulsar and/or Strike Needle. The Magnus line is highly regarded for slapping Devilites, but in my experience Blaster is much safer due to mobility and just as powerful due to higher volume of fire. I think it's mostly inertia from before Blaster got some heavy buffing, so it eclipsed Magnus for that.

You might want a sword as a sidearm, something with heavy knockback, because none of your guns have impressive knockback. Drop Argent, and get something ffor sticky situations.

Alchemers work fine against devilites. Magnus has horrible dps, so if you land a ricochet every now and again, you'll do about the same damage. Granted, you'd be better off learning to blitz devilites or picking up a toothpick, but callahan does not offer as much of an advantage as you might think.

AP has fallen out of popularity. As has making FSC videos. Use antigua line only if you don't like alchemers. Because alchemers are better.

Effective gunners charge spam or switch shoot. The choice affects what gear you should use.

In my experience, Valiance > Callahan for beasts and fiends. But really, just get a toothpick like Blueflood said. I don't know why there's so much dislike for Argent Peacemaker, it's the most versatile gun I own. Great for turrets, FSC, breaking things, killing more things and more. If you're in full Shadowsun, it has perfectly fine DPS considering how fast you can shoot out the clip.

To be entirely honest, it is my opinion that all of the guns in spiral knights are fun to use... and keep in mind that social functionality aside, this is almost entirely a game about getting gear.

That being said, I'd recommend getting a sudaruska as a side weapon. Having 4 guns is somewhat redundant, as is having 3. When I gun, a typical loadout would be something like:

Mask of Seerus
Grey Feather Suit/Nameless poncho (depending on whether I need defense+status or...)
Swift Strike Buckler/any defensive shield

Sudaruska/Triglav
Magma driver
Umbra driver

And this would be used on a level like clockwork tunnels.

So why isn't this redundant?

If I encounter.... ....I will use

Construct/Undead.....Magma driver+Sudaruska/Triglav
Gremlins/Slimes......Umbra driver+Sudaruska/Triglav
Beasts......Triglav/sudaruska
devilites/gorgos......magma driver
All other fiends.......triglav/sudaruska

Having 2 weapons to fight an enemy with can help you a great deal, rather than lugging around that one dead weight weapon. Like callahan. If there are only a handful of beasts on a level, why bother bringing your blitz needle? Sure it might be the "best thing" for beasts, but you can get by on normal damage.

I don't recommend the Kat Cowl as your first helmet if you don't have 5S gear already.

You also won't really notice a benefit of ASI gear with Sentenza/Argent lines--those guns desperately need Gun Damage boosts anyway.

Comment on AP vs Alchemer (Elemental guns):

Overall, when you have plenty of room to kite, it doesn't matter what gun you use because you can outrun/outdodge everything with relative ease.

Argent is a terrible main weapon because it can't handle mobs. It's a good support weapon for weakening single targets at a distance. It really requires a ton of room to kite around. I believe it takes roughly 3 Argent shots to match 1 slash of Divine Avenger in FSC (~130 each shot vs ~400). It really feels more like a support gun than anything and I bring it to finish off weakened zombies or to weaken zombies at a distance as I walk over to give them a slash. But good luck trying to fight off 2 Mecha Knights with an Argent in a Battle Arena or something. (I don't have a Nova so I can't comment if it's better than Argent in FSC. It probably is, though.)

But even Blitz Needle outdamages Argent against the Slags in FSC, and if I'm going from 4 weapon loadout to 3, Argent is the first to go.

I also like Argent for fighting Roarmulus Twins--a charge shot takes out the head in every phase because the bird does ~130x4 damage (on damage VH; on max damage it's around 140x4) I haven't found much else use for the charge shot, but I think the RT mission is one where Argent does "really well" at only because alchemers are just bad there.

Alchemer charge shots are very welcome, especially if you have CTR Max one way or another. The regular shots are good for running around mobs in circles and spreading status around--but the reduced range on the regular shot is a huge annoyance. Even worse is that the shot explosions feel somewhat ambiguous when fighting things with small hit boxes (Kat, Devilite, etc), where the shots themselves explode but no damage is dealt, which makes Argent my preferred gun for taking them out.

Both are good against turrets: AP for mobility and dodging multiple turret fire, Alchemer for ninja charged shot kills before aggro. Don't have a pulsar so can't comment on that line. If you have a wall to hide behind, alchemer is easily better since you can charge a shot from safety and pick them off one at a time.

Alchemer also leads to some interesting setups--for example, two Lumbers spawning side by side get insta-KO'd by an Alchemer charge shot directly inbetween them. It is a much more mob-friendly gun than Argent.

Altogether, I like both guns. There are some situations which I will bring one over the other, but since the majority of monster spawns are in the form of mobs, the inability to crowd control at all with Argent makes me prefer Alchemer.

Hey, I'm a gunslinger too, (not a vanguard yet though) and heres what I think. Nova Driver is good, but if the object is turret destruction, the storm driver still OHKO's w/ charge, while also shocking with normal bullets. My planned loadout for 5* looked alot like yours but after getting a sentenza, (and using it on rjp), I realized my volt driver could match it with CTR VH. Soon after, I got a shadowtech alchemer which does easily comparable damage, and allows for alchemer switching. I don't have AP but I hear that it works fantastically. Blitz (I have strike b/c it OHKO's zombies + trojans anyways) is amazing for FSC. For armor, since you are running alchemer(s) and Needle you might want to consider chaos, since the CTR would put you at CTR VH (w/ one piece) for all of your guns. Chaos's status' weakness matter little since you (hopefully) stay back with your hit and run strategy. Chaos is also considered OP and is shunned upon.

Also, do you even need AP? Nova outdamages in groups, and single target with practice. Other alchemers can inflict status, and you might find a support bomb or a sword more useful for breaking grass. (and fighting ...)

Callahan is really UP.

I have both callahan and valiance, and I find more valiance more effective than callahan vs fiends. Valiance allows you to fire 2 bullets without reloading, while callahan only lets you fire one without reloading. Valiance also allows you to continusously move while firing, which is ESSENTIAL vs devilites. I went into the guild training hall and tested the damage of both gun's shots. At very high damage bonus valiance did 2 shots for 150 damage vs 252 per shot per vulnerble for the callahan.

As a side note, consider having at least 1 piece of the chaos set, because this will boost other weapon types, like possibly a piercing sword (gunning beasts is incrediby annoying and tedious), or if you decide to make a bombing/swording/hybrid loadout, and as a gunner the defensive debuffs should'nt matter anyways.