You could be experiencing RFI. I am a ham radio operator and run a 1000 watt amp to contact distant stations around the world at certain times. One of your neighbors could be a ham radio operator. If you see a big antenna on top of a large tower that could be the source of RFI, radio frequency...
What brand cases are we talking about? Are they for a bolt action or semi auto? Are you loading for accuracy, plinking, hunting or load development? They are completely usable but dependent on your purpose.
Since the concusses so far is GAP, which I completely agree, what configuration rifle would suit your needs best? 20" or longer barrel? Optics and mounts? Trigger? Bipod?
Once you have decided on the gun, you must think of accessories, right?