Yeah Bloody Mary uses a timed meter and needs accuracy. You want to land a headshot with the meter full to set your next shots to deal the best damage, have best fire rate, lowest recoil, uses less silencer, etc. If you don't have a max quality shot by either missing the headshot or not getting the meter full, it will just be lower quality in all of these categories, so if you miss, just reload and try again. I'm not an accurate gunfighter so it's not my cup of tea, but if you are good at headshots, it'll be good.
Without in-game stat numbers to judge like in Warframe, user reported numbers may not be accurate. There's lots of different locations that shots will do different damage on an enemy (head/neck/shoulder/body/foot etc) plus the Forge system will skew these numbers even further. You could build with 0 stats to find the base, but guns cost a lot of gold to build to purposefully waste a blueprint and gold, and also nobody builds to 0 anyways so it's not all that realistic. Also also, guns get buffed or nerfed sometimes. Bloody Mary for example has been given a damage buff in a recent update and sometimes stats change WITHOUT being included in the patch notes. Like Bloody Mary's fire rate was not affected by shot quality back when I made my video, but now it does shoot fast if you make a good shot. Not sure when that change happened because it's nowhere in any patch notes, they only mentioned a damage buff in a previous patch.
Anyways the community has been doing exactly what you're looking for on the discord, you can check it out if you want. Wiki is a WIP by a few users, I'm not versed in how wikis work so I can't really help there:
Vindicta Anima (Harec) Headshot 148 Body 77 Limbs 37 Zoom up to 300%
Aura Mortis (Harec) Headshot 184 Body 96 Limbs 22 Zoom up to 400%
Ignis Fugit (Harec) (pending)
Ferox Impetus (Harec) Headshot 78 Body 26 Limbs 14 Zoom up to 150%
Phax Utt-17 (Shae) Low 25 Mid 40 High 425
Light Pulse (Shae) (Pending)
Focus KAA7 (Shae) Low 15 Mid 37 High 76
Asi'Dagan (Shae) Low Mid 40 High 160
KLT-13 (Doldren) Limbs 23 Chest 49 Headshot 184
JK-5 (Doldren) (Pending)
Bloody Mary (Doldren) (Pending)
Novera CC1-1212 (Alicia) Low 17 High 28 Crit x2
Vinc "Eager" 21-1 (Alicia) Low 9 High 49 Crit % in the forge
Smoking Daisy (Alicia) Low 56 - 57 High 73 Crit x2
Rock'n'Roll (Alicia) (Pending)
Infected MM-6C (H.I.V.E.) (Pending)
RACEME (H.I.V.E.) (Pending)
WASP (H.I.V.E.) (Pending)
Dolores (Lycus) Low 13 Mid 40 High 106
Shit Happens (Lycus) Low 11 Mid 41 High 89
Spinning Coin (Lycus) vertical 13 - 245 horizontal 39 - 70
Pepper Pot (Lycus) Low 17 Mid 48 High 150
Magnet-Z1 (Ayana) Direct dmg 15 Explosion dmg 75-83
Makilium (Ayana) (Pending)
Legacy (Ayana) (Pending)
MPFA Rimbaud (Hans) 48 - 56
Ansgar "WARM" MM1 (Hans) (Pending)
USU-21 (Hans) Low 33 Normal 42 High 56 (velocity)
Heaven's Bane K-8 (Hans) (Pending)
O.SMERCH S6 (Konstantin) Limbs 10 Chest 20 Head 27
O.SHSTORM BV (Konstantin) 13-37
HORNET HH3 (Konstantin) Limbs 4 Chest 11 Head 24
O.Tsiklon UV9 (Konstantin) (Pending)
and this
http://raiders-of-the-broken-planet.wikia.com/wiki/Raiders_of_the_Broken_Planet_Wiki