I think you have just copied the fire sprites from my Railgun Enhanced. If you did so, please credit me. Thank you.
The firing sprites are identical, and even have the same file size, so it looks like that's indeed the case--although, in fairness, I didn't see anything in the Railgun Enhanced WAD that credited the new muzzle flash edits, so it could have escaped his attention. colboh, could you update the submission's credits accordingly? It doesn't sound like NourPrince objects to you using the flash sprites as long as he's credited. (BTW, good job on the flash sprites, NourPrince.)
Also, the railgun attack parameters in DECORATE throws a warning at runtime--"pufftype" is "0" in the list of parameters, which ZDoom apparently doesn't like. You can leave the empty parameters blank and you should be OK.
I do have to say that I love the autoaim, though. I did play around with the DECORATE a bit, and made a discovery--it doesn't look like the "A_FireBullets" actually has any effect on the autoaim. I commented it out just to see what happened, and it continued to autoaim using "A_CustomRailgun" alone. Someone else can correct me if there's some under-the-hood difference I'm not aware of, but it looks like "A_FireBullets" is unnecessary. (But it doesn't seem to hurt anything, either.) Regardless, I think this is brilliant; I would have never thought of using the monster attack function to get autoaim. I do use freelook, but I don't typically use a mouse (or gamepad) because I'm weird like that, so this modification is very appreciated for someone like myself.
I think the damage and ammo consumption are too high, but I always felt the same about the original Skulltag version anyways. So that's open for opinion.