If you are satisfied the gas blocks are aligned properly, but thinking your uppers are undergassed, take the carbine lower, pop out the buffer, and with a hammer and small punch tap out the roll pin that is holding on the rubber piece. Remove the rubber piece, and remove one of the three weights inside the buffer. Reassemble the rubber piece and roll pin onto the buffer body. Test fire. Better? There you go. No better? You can try taking a second weight out and test firing.
If you're undergassed, lightening the buffer may get you running. At that point you can either run a lighter buffer or see about opening your barrel's gas port. Another way to test a carbine lower is with a Sprinco yellow carbine spring. If severely undergassed, you may have to run the lighter buffer and the Sprinco yellow spring together.
