Just finished assembling my lower, wanted to make sure I didn't miss anything.

[springy101]

I just finished putting together my lower and have 2 pieces left, the stock mag release button and a big thick spring. Put my bullet button so I knew I would have the mag release button left but did I miss that big spring somewhere?

[DanHuuN]

I believe the spring is for the original mag release. The bullet button has a spring included thus not needing the original spring.

[Agro]

I believe the spring is for the original mag release. The bullet button has a spring included thus not needing the original spring.

I concur. You can't really miss anything and have the lower function properly. Verify that the bolt catch spring is in place. Verify that the front/rear take down pins have the detent in and springs. You'll feel it as you move them in/out. Verify that the BB releases the mag properly, verify that your selector detent is functioning and thats obvious or the selector will slide right out. Then the fire control group needs to be tested. Dont let the hammer hit the bolt catch piece, but put your thumb over it and let the hammer fall and then re-cock it. I've seen many people mess up and install the hammer spring upside down. It might seem like it's working properly, but it isn't . Verify the selector in fact works as intended in Fire/Safe. Anyhow, you get the idea, good job.