After a long hiatus from Fallout 3, I decided to start playing the game again, and am currently trying to get the "Weaponsmith" Achievement on XBOX 360. I have built one of every weapon in the game except the Railway Rifle. Its been a while, and I can't remember if I need the schematics to build the gun; or if I can just collect the parts and build it without having the schematics beforehand. I'm pretty sure I need the schematics first, but I can't remember which NPC I saw selling them. I think it was on one of the travelling merchants, but I'm not sure.

Anyways, do I have to the schematics first? And if so, who sells it? Or, is there somewhere I can go and find the schematics laying around as loot?

Thanks in advance for any replies.

You get it from Abraham Washington after you complete the declaration of independence quest.

I think that quest is an achievement as well, so that will work out fine. Two achievements for one quest. Thanks very much.

You can also buy it in Underworld.

the schematics, you need first. there is a schematic for the railway rifle at a power station that is north of minefield. there are two building, the smaller building has it. it is on a workbench,