Artillery 5
Capacity Boost
Razor Sharp
Evade Extender (2 preferred)
Evade Window (3 min)
Slinger Capacity 3
Barroth Bluff 1 - Wide 4, 5
Hidden Cannon 1 (Narga) - Wide 4, 5
Bazelpride - Wide 5
Ruinous Eradication - Wide 5
Glutton's Fang (Jagras) - Normal 4 to 6
Hoarcry Cannon (Shrieking Legiana) - Normal 6
Black Ephyra (Namielle) - Normal 6
Eisritter (Velkhana) - Normal 6
Queen's Panoply (Gold Rathian) - Normal 6
Stygian Avaritia (Stygian Zinogre) - Normal 7
Crimson Ember (Viper Kadachi) - Long 4 to 6
Deathlance Vaal Spysa (Blackveil Vaal) - Long 6
True Fatalis Gunlance - Normal 7
Lightbreak (Raging Brachydios) - Wide 7
Safi - Long 6
Been using GL all through Iceborne and been using the new tool on every single hunt. I have plenty of stuff that wasn't listed or that I can go more in-depth on:
Wyvernstake blast has 3 tiers of explosion: weak, normal, and strong. Weak explosions are triggered by standard shelling, normal explosions are triggered by full bursts and normal wyvernstake's final explosion, and strong explosions are triggered by charge shots and wyvern fire.
The actual damage you deal with the attack does not matter, simply the type of attack used. A Normal 1 charged shell will trigger a strong explosion just like a Long 6 charge shell.
Ground ammo like stones, redpits, mosses, etc will last shorter than powerful ammo dropped by monsters, however the damage on the blast will be the same for both types.
How much ammo you load into it also affects the time proportionally to the percentage of ammo you had - Shooting a single stone and loading (19/20) will lower the stake time, but not as much as shooting a single torch (4/5) and loading. This means loading a full ammo slinger will give you the same time as long as you haven't fired any, regardless of the actual number. 3 pierce pods will give you the same time as 2 thorn pods, and 20 stone will give you the same time as 7 brightmoss.
Stonethrower/Slinger Capacity ups the time the stake is attached to the monster by virtue of throwing more ammo in.
Artillery, like you said, has no effect at all on the actual stake damage. To note: Wyvernfire will generally trigger the explosion 3 times, since it's 3 strong hits.
Shell Weak Normal Strong
Normal 5 22 36 66
Normal 6 26 43 78
Long 5 28 46 84
Long 6 35 58 105
Wide 5 32 53 96
While your regular shelling is only a light interrupt that's negated by Flinch Free 1, the strong explosions from Wyvernstake Blast will cause a trip that requires Flinch Free 3 to be completely negated. Unsure about the medium or weak explosions.
Edit: The damage from other players triggering your explosions is negligible for the most part. However, every little counts and while it's not something that should be built around it's a nice little bonus.
Other players' attacks can trigger your Wyvernstake blast - And not just Gunlancers! I haven't been able to test all interactions yet, but I can confirm a Dragonpiercer was able to trigger my Long 6 wyvernstake for 11 damage per hit. My guess is other "explosive" attacks will trigger it, like Sticky shot or Cluster shot.
This also means 4 Long 6 GL users with Artillery 5 and 4 Wyvernstake blasters aimed at similar spots will be doing 170 + 420 damage on every single charge shell. Each person dealing nearly 600 damage every shell... Assuming you can attach one Wyvernstake per player to the same monster as I haven't been able to try that yet.