My biggest complaint falls on the "AR" series weapons. That includes the "Serivice Rifle" (AR-15/M-16 semi automatic) and the Assualt Rifle (M4-A1 full auto). The "Marksman Rifle" (M4) is also an AR series, but I'm not including that since it comes with a scope. For starters, the Service Rifle and the Assualt Rifle use 2 different ammo types. I'm not sure at what point in the history of the entire world, that a 5mm round ever exisited, but since both rifles are based on the "AR" platform", they should both use 5.56mm ammo. 5mm ammo shouldn't even exist in this game. The rifles from Fallout 3 both used 5.56 ammo, so, you would think that would have carried over? Regardless, my complaint is with the Iron Sights. On both rifles, the frames of the iron sights, when zooming, take up 25% or more of the screen and are so thick that you can barely track what you are aiming at (unless it's standing still). This is a big problem if you are not using VATS since this weapons are meant for medium to close combat. Both of these rifles need to be re-tooled to thin out the walls of the carrying handle so that they don't obstuct the view as much as they currently do. This distraction is so annoying that I hardly use either of the weapons. In fact, I don't use any AR variant after level 15. By the time you get a hold of the Marksman Rifle, the 5.56mm round is all but useless except for the Light Machine Gun. As a side note, the rate-of-fire with the Assualt rifle is way to high and "laggy" when squezzing the trigger. Conversaly, the Service Rifle is way to slow in it's firing rate and also laggy.
Next, and more prominetly, are the various battle rifles, bolt-cation and semi-auto alike. Starting with Varmint rifle w/o scope, it seems like long range shots (when enemy head is smaller the front sight apature) are favored at the right most portion of the the front sight (while kneeling). The Comboy Repeater seems to hit at the top right potion of the front sight. The Hunting Rifle seems to hit where ever the "green dot" is (well below the top of the front sight post), which makes long range head shots impossible since the front sight post covers up what you are aiming for. Grant it, once you add a scope to these weapons (where applicable), they are dead-on accurate. Ideally, the front sight post should cut-in-half, the target that you are aiming for and the bullet should intersect "horizontally at the dead center of the front sight post and "vertically" where the front sight post cuts-in-half the target in question. The Gun "This Machine" (M1 Garand- misson reward) is the most accurate with Iron Sights, but it too has a right side bias at long range. The thing is, battle rifles are "supposed to be "sniper rifles" with out scopes. I rely on these weapons to fill in a role that falls in between my Anti-Material Rifle and my Sub-machine gun. I hope Bethesda can "refocus" the sights on these weapons. Note: I haven't used the Trail Gun or Brush Gun enough to comment on their bias.