Playing ITR with multiple mods adding custom items might feel inconsistent. While the mod authors are making every gun usefull from gameplay perspective weapon damage values are all over the place. Furthermore if you are not familiar with modding - you dont even know how to check weapon stats. This is my attempt to adjust those values so that every weapon could be understood intuitively.

The STALKER mod was used as a base for standartization. Every weapon is just a tool to fire the bullet. The muzzle velocity, recoil and damage are MOSLTY based on cartridge. You can get the basic idea of weapon stats on this spreadsheet: Stalker spreadsheet Notice how every weapon is grouped by caliber and case length.

IS THIS SUPPOSED TO BE BALANCED? Not necesserily. This is supposed to be somewhat realistic, logical and intuitive.

Example 1: Mosin nagant and SVD are both using 7.62x54R. But Mosin is bolt action and SVD - semi auto. Furthermore SVD was developed more recently. It's hard to find justification for old Mosin weapon to be better in any significant way (Bolt action guns dont jam i guess ¯\_(ツ)_/¯ ) 
Example 2: Glock 17 has twice shorter barrel than MP5. So the same 9x19 bullet fired from Glock will do a little bit less damage and fly a little bit slower than when fired from MP5.

THE MAIN LOGIC BEHIND STANDARTIZATION:
1) Are weapons using the same rounds?
This is the main deciding factor. Weapons are going to have very similar recoil, damage, muzzle velocity, loudness.
2) Is that a short barrel/compact weapon variant? (AK74U, MP5K, G36C, M4CQB)
The round flies slightly slower, is less accurate and deals less damage.
3) Heavier weapon? (M16A1, G36)
Opposite to the ones above - less recoil because of the weapon weight.
4) Is it an old weapon? (Mosin, AKM)
Less accurate than similar weapon that was made by todays weaponsmiths.
5) Different weapon designs, less moving parts, high quality materials?
Less durability damage per shot, more accuracy.

Compatibility:

Stalker mod -  Fixes few oversights. Such as AUG being twice louder (Not sound file, but range at which enemies "hear" gunshots) than it should.
z_STANDART_STALKERWeaponStats_WeaponInfos_P file - replaces original WeaponInfos file and overwrites changes from STALKER mod with updated stats.
The mod doesnt add any new weapons so the file will stay relevant for forseeable future.

Chuck's custom items - Stalker dependency used as base - mostly Insignificant changes but very significant changes for .45ACP weapons
(Damage wise UMP45 is more like MP5 while M1911A1 and M45 pistols are more like M9 instead of the original where pistols where stronger than smg)
z_STANDART_DT_WeaponInfos_Chuck_P file replaces Chuck's DT_WeaponInfos_Chuck file. STANDARTISATION file changes stats for weapons added by Chuck's custom items mod if you chose stalker preset during instalation. (3.0.43)
Author releases a bunch of new weapons and goes back to slumber for a while. File should stay relevant for a while.

R3mains' custom items - Stalker dependency used as base - quite significant changes across most weapons.
Main difference - weapons with similar rounds have similar performance. Weapons with integrated supressors (SIG MCX VIRTUS and SIG MCX SPEAR "XM7") have around 40% reduced gunfire sound range, but require more maintenance (They break faster, jam more often). They use standard ammunition that flies at supersonic speeds so they are still more noisy than vanilla Vintorez or VAL that uses special 9x39 ammo.
z_STANDART_DT_WeaponInfosANDUpgradeInfos_User5_Stalker_P file replaces DT_WeaponInfos_User5_Stalker and DT_UpgradeInfos_User5_stalker files. STANDARTIZATION file changes stats for weapons added by R3mains custom items mod if you chose stalker preset during instalation. 
Additionally makes weapon upgrades consistent when changing some of the R3mains weapon calibers when using upgrade box.
Author consistently keeps adding new weapons. Bug fixes, attachments or mags are ok, but as soon as new weapon is released my file will not have infomation about it. Currently updated for all weapons that exist in R3mains' Custom Items V1.17.1