Brewers Best kits are generally very good from what I've read here.
Is this the kit?
http://www.brewersbestkits.com/assets/1013_americanpaleale_recipe.pdf
I did not do secondary fermentation.
Not racking to a "secondary" (vessel) was a good decision. Secondaries aren't needed for most beers, there's nothing to cure, and may or will cause problems.
It looks like you're used to drinking craft beer, so you do have experience with various and larger amounts of bitterness.
Always do a 2nd round. I'd say have another one and keep some notes on your taste (and aroma) experience.
Your mostly flat sample at bottling time is not a good representation of what the beer will be when properly conditioned and carbonated. Sure it has all the makings, but there's a lot of change during (bottle) conditioning and the carbonation process.
Carbonation enhances the sensation of drinking beer, bringing many of the flavors and aromatics up front. It also stimulates the palate and receptors in the nasal passage for a better sensory experience. Along with that comes a slightly higher acidity, which is beneficial for perception and separation of many flavors and aromas.
AFAIK, bitterness is not driven or enhanced by carbonation, but you may be able to taste it more since it's not as muddled as that early flat sample you had previously.
Most bitterness in beer comes from the hops, but darker malts (for darker beers) will add it too, similar to bitterness in coffee yet different than that from hops.
Astringency is another factor, often confused with bitterness. Astringency exhibits itself more as a dryness in the back of the mouth, cheeks, and throat, compare to sucking on a tea bag, while bitterness is tasted on the back of the tongue.
Astringency could come from increased tanning extraction due to over-steeping grain (steeping too long). Also when steeping at too high temps (>165F) and a pH that's too high (>5.8).
There's a pound of specialty malt in the kit that needed to be steeped.
- Did you follow the steeping instructions to a T?
- Could it be astringency?
- What water did you use for brewing?