I purchased this SA7-450-SM gas block after experiencing blown primers and cycling issues in a 16&quot; 5.56mm, mid-length barrel paired with an AR-15 bolt carrier. I judged the barrel gas hole was too large for my original GB7-450 gas block and H1 buffer in combination with the dwell length and BCG. After replacing the fixed gas block with this adjustable and swapping buffers, the carbine cycles flawlessly (with either an H2 or H3 buffer). I've bought a second SA7-450-SM for a 6.5 Grendel upper and will get a third for a 224 Valkyrie upper. The adjustments are excellent, allow for fine tuning and will be a bonus for suppression.