Blog
August 26. 2026
What Does the RAS Selector Do
Most AR-15 builders know their selector has two positions: safe and fire. The RAS selector has three, and the third…
August 24. 2026
The History of the MP5K
The MP5K is often described as a compact version of the MP5, but that framing undersells what HK actually set…
August 20. 2026
MP5K Host Compatibility
Builders who choose an MP5K host based on price and availability rather than documented compatibility patterns discover the fitting requirements…
August 19. 2026
MP5K vs Full-Size MP5 — Mechanical Differences
The MP5K looks like a compact version of the full-size MP5 and shares most of its external design language. The…
August 18. 2026
Common AR-9 Build Mistakes
Most AR-9 build mistakes don't happen because builders are careless. They happen because the platform looks familiar enough that the…
August 17. 2026
AR-9 vs AR-15: What Actually Changes
Builders who come to the AR-9 from the AR-15 assume the transition is straightforward: same lower, same upper interface, familiar…
August 15. 2026
Legal vs Illegal Firearm Modifications — What Builders Need to Know
Most builders who run into legal problems with firearm modifications weren't trying to break the law. They assumed federal compliance…
August 14. 2026
AR-9 Magazine Compatibility: What Works and Why
AR-9 builders who assume any 9mm magazine will work in any AR-9 lower discover the problem at the range, not…
August 12. 2026
How to Read Shot Groups and Diagnose Shooting Errors
Most shooters look at a shot group and see a result. The ones who improve fastest look at the same…