I think most of this has been found already from what I've seen, but I did some testing on the weapons myself and just jotted them down in my notes:
~~~~MAIN WEAPONS~~~~
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Chargers
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-E-liter 3k
7.5 yard range
Holds 3.5 charges
Splatting potential at ~75% charge
-Kelp Splatterscope
6.25 yard range
Holds 5.8 charges
Splatting potential at 100% charge
-Squiffer
4.25 yard range
Holds 9.5 charges
Splatting potential at 100% charge
-Splat Charger
5.75 yard range
Holds 4.5 charges
Splatting potential at 100% charge
-Hero Charger Replica
-same as Splat Charger-
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Shooters
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-Splattershot Jr
3 yard range
Holds ~16 seconds of continual fire
Splatting potential with 4 direct hits
1.5 yard spread
-Splattershot
3.6 yard range
Holds ~11 seconds of continual fire
Splatting potential with 3 direct hits
.75 yard spread
-.52 Gal
3.6 yard range
Holds ~12 seconds of continual fire
Splatting potential with 2 direct hits
.75 yard spread
-N-ZAP '85
3.6 yard range
Holds ~10 seconds of continual fire
Splatting potential in 4 shots
.75 yard spread
-Aerospray MG/RG
3 yard range
Holds ~13 seconds of continual fire
Splatting potential in 5 shots
1.5 yard spread
-Jet Squelcher
5.5 yard range
Holds ~7.5 seconds of continual fire
Splatting potential in 4 shots
.5 yard spread
-Blaster
2.5 yard range
Holds ~12 seconds of continual fire
Splatting potential in 1 shot (2 from blast)
.5 yard spread (1.25 from blast)
-Splattershot Pro
4.5 yard range
Holds ~6.5 seconds of continual fire
Splatting potential in 3 shots
.5 yard spread
-.96 Gal
4.5 yard range
Holds ~8 seconds of continual fire
Splatting potential in 2 shots
.75 yard spread
-Rapid Blaster
3.5 yard range
Holds ~8 seconds of continual fire
Splatting potential in 2 shots (3 from blast)
.5 yard spread (1.25 from blast)
-Dual Jet Squelcher
4.5 yard range
Holds ~8 seconds of continual fire
Splatting potential in 4 shots
.75 yard spread
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Rollers
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-Roller
3.5 yard range
Holds 11 shots, or ~10 seconds of constant rolling
Splatting potential in 4 hits (max range)
1 yard width
-Dynamo Roller
5.25 yard range
Holds 6 shots, or ~12 seconds of constant rolling
Splatting potential in 4 hits (max range)
1.25 yard width
~~~~SUB WEAPONS~~~~
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-Sprinkler
2.5 yard range (5 yards from edge to edge)
Only one active at a time
-Burst bomb
3.25 yard range
1 yard of spread from explosion (~2 yards of "shrapnel")
4 per tank
Splatting potential in 2 hits (5 from spread)
-Ink Mine
0 yard range
1.75 yard spread
Splatting potential closer to center of the mine (~.5 yards from center)
-Splat Bomb
3.5 yard range
1.25 yard spread from explosion (~4.5 yards of "shrapnel")
1 per tank
Splatting potential from explosion damage
Detonates ~1 second after landing
-Seeker
Infinite range (goes until it hits a wall/target)
1 yard spread from explosion
1 per tank
Splatting potential from direct hit
-Splash Wall
1.25 yard range
1 yard width
~6 seconds long
-Point Sensor
3.25 yard range
~3 yard Width
Lasts ~10 seconds
-Disruptor
3.25 yard range
~2 yard width
Lasts ~5 seconds
-Suction Bomb
3.25 yard range
1.75 yard blast radius (~4 yards of "shrapnel")
detonates after ~1.5 seconds of sticking to a surface
~~~~SPECIALS~~~~
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-Bubbler
Lasts 5 seconds
-Bomb Rush
Lasts 6 seconds
Can throw 16 Burst Bombs or 11 Splat Bombs
-Inkzooka
Lasts 6 seconds
Can shoot 6 times
6.75 yard range
-Killer Wail
Lasts 4 seconds (1 second windup)
Infinite range
~2 yard width
-Echolocator
Lasts 12 seconds
-Kraken
Lasts 6 seconds
Covers .5 width while moving
-Inkstrike
Covers 3.75 yards (end to end)
3 second delay (from when location is chosen)
For reference, "Yard" in this case means the distance between two lines in the training area.
Also sorry about the length, don't really have a better way to post it :s