So, finally got the rifle together and took it to the range for the first time. Since I had to sight my hunting rifle, I only had time to run a 100 rounds down the pipe. In that 100 rounds, I had 6!!!!!!! FTFs!!!!!!! What should I be looking for? I re-magazined the 6 rounds and 2 of them fired, they are also the 2 that I used the foreward assist to make sure the bolt was all the way foreward because on all the FTFs the hammer drop didn't feel quite right (light).

-buffer spring not strong enough?
-new parts not broken in yet, machine markings causing fully feeding problems?
-crap ammo?
-action gummed up (although I don't think possible)?
-FSB gas hole misaligned? (NO failure to feeds though)

The rifle is a Spikes lower that I put a DPMS LPK into. Upper is a Del-Ton 16" this is it:http://www.del-ton.com/Del_Ton_AR_15...y_p/dt2003.htm Using Magpul Pmags, tried several.
Didn't use crap ammo because I was sighting my cheap red dot. Used Federal 55grn (walmart box)(I know 55grn isn't optimum for a 1-7 barrel, but it shoots fine and no keyholing, yes, 62grn+ would be better). When plinking, the steel cased ammo didn't have an FTF, but only shot 30 (fired after the brass, so polymer coating not the cause). Upper and lower were cleaned to a point of sterile (delton uppers have a ton of crap all over them) and then lubricated lightly on wear points with Hopps lubricant. Gas rings all perfect, new and intact.

Anything else I should be looking for? Any and all ideas are apprecieated. I am not too worried, I am figuring it is new gun break in stuff, but this is my first AR, so want ideas. Thanks!
J.C.