The mod tools aren't up to date with the current patches for some time now although I'm not sure what update its on. I think it might actually be on an update that is prior to the B-4 changes.
By default, the units within the mod will use the current patch but any clones that you make will use the mod's values.
ebps\races\soviet\team_weapons\soviet_field_artillery\m1931_203mm_b-4_howitzer_artillery_commander_mp
I think this is the one you will want to clone. If you right click on anything within the attribute editor it will give you an option to "find all references". This tells you what it links to and what you will want to edit.
abilities\soviet\modal_ability\artillery\artillery_barrage_ability\b4_203mm_barrage_commander_mp
This ability fires a single shot which might be what you're looking for.
So overall you'll need to clone the references in ebps, weapon, and abilities categories.
Thank you for the reply, Sayoka. If it weren't for people like you, and the guys on reddit who suggested that the attributes were out-dated and I could just clone & build, I would've never got to try the B4 in pre-nerf state.
I actually came to certain conclusions by myself. After cloning ebps+sbps+weapons category B4 files, my B4 was still firing 3 shots. So I started tracing where those entities link to for information, and I eventually found out about the "abilities" categories and the fact that B-4 has it's own special barrage.
What is interesting, is that there are several more "B4" barrages in there. One of them fires 4 shots, another one 8, if I'm not mistaken. I did not spend time digging through, but my guess is that those are either for Railway artillery, or for Singleplayer, or just old relics that never were used.
Had there not been anyone on reddit to suggest cloning, your reply would've been the only one to save the situation. Thanks again, Sayoka.