TSA Restricts .50 Caliber Ammunition
Quote from SCI:

It has recently come to the attention of SCI that the Transportation Security Administration has begun to restrict individuals from flying with .50 caliber ammunition. This does not prevent individuals from flying with their .50 cal or larger rifles, most notably being the .577 and the .505. SCI has been communicating with the NRA to have this current restriction lifted. To read NRA-ILA’s latest information please go to this link: http://www.nraila.org/Legislation/Federal/Read.aspx?id=4002