Well, I found out anything before 2004 uses metric and anything after, uses 6-48 thread the only thing is I don't know how to tell how old mine is by the serial number. I bought mine new but, it was (old stock) and was sitting on the rack a long time. I got it home and removed the bolt to give it a good cleaning and noticed the plastic bolt shroud was cracked. I contacted Beretta USA and when I gave the serial # the man asked if it was a new gun because it was manufactured 6 years ago. I explained it was new just, old stock and I had the proof of purchase receit. He went ahead and sent a new shroud 6 years ago would mean 2007 so, can I assume the receiver would be tapped for the standard Weaver 6-48 thread? I wish I knew another way to verify the date of manufacture. I've noticed while searching the net I ran across at least, three people who had the same concerns about the screws but they did, get them to go in so maybe I'll just put a dab of lok-tite and give it a go. Thanks!