Adjustable Gas Block Question (Superlative Arms Clamp-On)

I recently built an AR15 and put a superlative arms adjustable gas block on it. I took it to the range for tuning today and noticed there is a "sweet spot," so to speak. In this position, the rifle will fire and the bolt will lock on the last round. However, literally 1/4 turn in either direction will cause the bolt to fail to close on the final round. Is this normal? Apparently the further you unscrew the pin for a "bleed off" gas block the more gas it bleeds and the less recoil there is. I can't tell if I'm getting a recoil reduction as I've never shot another AR before. I thought I followed the directions correctly but I'm a bit concerned now.

I'm not sure if this matter, but I'm using the BCM A5 buffer kit. I believe it uses the Vltor A5H0 buffer (3.8 oz).