My new Beretta shoots about 2.5"-3" to the left at @15-20 yards. The elevation is fine, and the pistol groups tightly. A couple others have shot it, with the same results, so I don't think its my technique.
I've tried drifting the rear sight to the right a little using about every method I know, short of  buying a sight pusher.
A guy on Berettaforum.net suggested that on his 92FS, he had the same problem, and that his sight/dovetail was tapered and would only slide from right to left, but no further to the left than the center of the slide. Is there any truth to this? If so, I'll pull the rear sight, and file it a little to fit better.
Thanks in advance.

Quoted: My new Beretta shoots about 2.5"-3" to the left at @15-20 yards. The elevation is fine, and the pistol groups tightly. A couple others have shot it, with the same results, so I don't think its my technique. I've tried drifting the rear sight to the right a little using about every method I know, short of  buying a sight pusher. A guy on Berettaforum.net suggested that on his 92FS, he had the same problem, and that his sight/dovetail was tapered and would only slide from right to left, but no further to the left than the center of the slide. Is there any truth to this? If so, I'll pull the rear sight, and file it a little to fit better. Thanks in advance.

YOU ARE MY VINDICATION!!!!!!! Among other things.  I have been scolded by certain people on here because I took the liberty of floating my sight to the right because my POI was left.  First off I had others shoot it to make sure it wasn't me.  And secondly since I floated it, it's been shooting pretty much right on.  Although I'm not saying that part of it isn't me.  But I think part of it is the pistol too.

OK, now that I got that off of my chest.  I put my slide in a vice, with leather around it, took a brass punch and hammer, and drifted my sight.  It did however marr the finish on the sight.  So you may be better off taking it to a professional with one of those tools.  I was kind of peeved because I did this with my 1911 and no such finish damage was done so I figured it would be safe on this pistol too.  But someone kind of eluded that I was stupid for doing it.  Well maybe, but like I said, it shoots dead on for me now.  Even at 200 yards.

Yeah, I posted in GD regarding this as well, and got several "Its sighted in at the factory" type remarks. Apparently it wasn't sighted in that well. If it was just my shooting it, and everyone else hit OK with it, that'd be one thing. But when several people I know to be reasonably good pistol shots group the same with it, what else is there?

I finally did get it to move, thanks to a little nudge from a hydraulic arbor press and some experimentation with spacers to keep the slide from rolling bottom-up under pressure.

FWIW, I can now drift it using a hammer and a brass drift punch. Maybe it was just seized up in one spot. I'm gonna shoot it in properly tommorow morning.

ETA- Try taking a piece of super-fine-grit sandpaper, a scotch-brite, or maybe a piece of steel wool to the side of the sight you boogered up. Maybe you can get the brass marks off. If that doesnt work, try one of those Birchwood-Casey touch-up pens. All you do is clean the surface with alcohol, let it evaporate, then apply the touch-up pen. It'll start to turn black gradually, and when you get it to the shade you want, just dab some water onto it to neutralize the solution. I've redone sights on a Glock and a couple Rugers like this, and they look good-as-new.