Let's get that ejection angle straightened out. You said about a 25 degree angle? From straight ahead where the barrel is pointing. Or more normally, if the barrel is pointing to 12 o'clock, then the brass is ejecting toward 2 o'clock? And how far away, six to ten feet? That would make sense if the brass is hitting the deflector hard, it would bounce forward to around 2 o'clock. Too long a gas pulse due to the extra 4" of barrel past the gas port.
If that's a fixed stock make sure it has a rifle buffer (5.5 oz?) and rifle spring (about 13.5"?). Also look at your bolt carrier and see if it's the M16 kind and properly sheilds the firing pin. Any extra weight might be your friend.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together. You'll remember the quality of a gun long after you forget how much you paid for it.
US Army 1966-69, VFW Life Member, Retired Geek