Saltwater60
.950 JDJ
That is with assault riffles only thanks to Obama and his fast and furious gun dealings.While there currently is no legal limit that I'm aware of to the number you can buy I have been told by my FFL that 3 or more firearms at the same time (or within a short timeframe) may raise a red flag with the ATF and cause them to start asking questions. Take this with a grain of salt but it's reasonable to assume with the political agenda of these lettered .gov agencies that if you're picking up many firearms at the same time someone may get curious.
Perhaps some FFLs will chime in. @Bullet Guy ?