You say the gun is "brand new" so I have to ask the typical question.
Have you disassembled, cleaned, and re-lubed the gun?
Firearms (with a few exceptions) come from the factory lubed for shipping, not shooting. The goop that most factories put on is a protective not a lubricant. Or maybe you are using too much lubricant or something too heavy? (just brainstorming here).
Also, there are things you simply aren't going to be able to "see" with your fingers, you should have a sighted person who knows guns inspect around the rails to make sure there isn't something funny going on. I had a chip of brass (tiny little thing) act like a wedge on one gun, caused me all kinds of grief until I finally found and removed the damned thing.