Hello, I recently started an RPG in minecraft in which it is basically an ordinary city and I came up with the great idea of ​​doing a mission that leads to military training and things like that and I realized that when I put the gun and use it the movement is multiplied when aiming with the weapon is perfect only it is the visualization towards other players I will leave a screenshot as a reference!

Can you send me a list of your mods? I know this is an issue because another mod you have installed is causing the issue.

of course here they are!
-AppleSkin-mc1.12-1.0.9.jar
-Bookshelf-1.12.2-2.3.585.jar
-Chisel-MC1.12.2-1.0.1.44.jar
-CreativeCore_v1.9.90_mc1.12.2.jar
-Currency-1.12.0-1.3.11.jar
-CustomNPCs_1.12.2-(01Oct19).jar
-ElevatorMod-1.12.2-1.3.12.jar
-EnchantingPlus-1.12.2-5.0.176.jar
-Galacticraft-Planets-1.12.2-4.0.2.244.jar
-GalacticraftCore-1.12.2-4.0.2.244.jar
-MCA-1.12.2-6.1.0-universal.jar
-MicdoodleCore-1.12.2-4.0.2.244.jar
-ModernLights-1.0.3_1.12.jar
-Morpheus-1.12.2-3.5.106.jar
-Pam's HarvestCraft 1.12.2zf.jar
-PlayerRevive_v1.2.28_mc1.12.2.jar
-RadixCore-1.12.x-2.2.1-universal.jar
-SpartanShields-1.12.2-1.5.4.jar
-StarWars[1.12.2]-8.9.jar
-[1.12.2] SecurityCraft v1.8.16.jar
-chiselsandbits-14.33.jar
-chococraft_1.12.1-0.9.1.52.jar
-comforts-1.12.2-1.4.1.2.jar
-emoticons-0.4-1.12.2-dist.jar
-extrautils2-1.12-1.9.9.jar
-fencejumper-1.12-1.0.5.jar
-foamflower-1.12-0.0.1.0.jar
-fossilsarcheology-8.0.3.jar
-furniture-6.3.1-1.12.2.jar
-future-mc-0.1.13.jar
-guns-0.15.3-1.12.2.jar
-jei_1.12.2-4.15.0.268.jar
-llibrary-1.7.17-1.12.2.jar
-malisiscore-1.12.2-6.5.1.jar
-malisisdoors-1.12.2-7.3.0.jar
-mclib-1.0.4-1.12.2.jar
-obfuscate-0.2.6-1.12.2.jar
-rustic-1.1.2.jar
-sparkshammers-1.12.2-1.9.2.jar
-tombstone-3.6.5-1.12.2.jar
-u_team_core-1.12.2-2.2.4.107.jar
-useful_backpacks-1.12.2-1.5.1.35.jar
-vending-1.12.2-3.0.1.2.jar
-worldedit-forge-mc1.12.2-6.1.10-SNAPSHOT-dist.jar

It's an issue with MicdoodleCore/GalacticraftCore. Having the same issue in a pack I was building. Was able to replicate the strange dual-weapon by just using these mods. As far as I can tell, there is no way to fix it with the given GC config options

I have the same problem.

Unfortuantely I don't maintain the 1.12 version anymore. In newer versions, the library Obfuscate which I use to render the weapons, now has better compatibility with mods. Going to close due to 1.12