First, just to let you know, I'm running GRA and WMX.
Here's what's got me going. I spent 10,000 caps to buy an assault carbine, and about another 15,000 buying things like extended magazine, forged receiver, and last but not least, a suppressor (which I actually bought first). So, I added the suppressor to the rifle, then bought the other stuff, and... couldn't add either one to the assault carbine. I'm not saying I was upset, but I kinda wanted to find a place to shove those mods... and maybe the rifle itself, if you know what I mean.
So, I go to Gunrunner's by new vegas, and there in the list is another assault rifle, but this one says (GRA). Well, okay, then I bought that GRA carbine for another roughly 10,000 caps, and also a suppressor that was available.
Okay, now I'm thinking I'll have it covered... but again the best laid mice of plans and men jumped up and bit me. the new rifle accepted the forged receiver and the extended magazine, but wouldn't take the suppressor.
Oddly enough, according to the FONV wiki, the only modification that the Assault Rifle (I'm assuming vanilla) will take is the extended magazine, and there is no suppressor shown for either version.
The thing that upsets me, is that the assault carbine does damage of 14, and DPS 160. The Assault Carbine GRA does 11 Dmg, and 156 DPS even though the Wiki shows it as a 13 dmg. So, if I want the more effective weapon, I should use the one with the suppressor only (by the way, the suppressor is not very effective). Just as bad, the grunt perk does not effect the GRA version, I'm uncertain about the other one, but I think it is effected by the grunt perk. In the end, it would seem that although the mods improve the condition, ammunition capacity, and rate of fire, the lesser rifle is actually the better rifle all things considered.
Why am I telling you this? Well, I just have to gripe to somebody, and I kind of thought some of you might want a heads up before you spend all those caps if you happen to have both of those mods like I do... At the moment, I'm carrying both of them, simply because I'm torn regarding which one I want to use, but one of them has to go. Character strength is not all that good.