RetroArms CNC Hop-up Chamber AR15 PRO – Black

CNC Hop-Up Chamber AR15 PRO by RetroArms
The AR15 PRO hop-up chamber by Czech manufacturer RetroArms is a premium choice for AEG replicas based on the AR15/M4 platform. Based on the proven BASIC version, the PRO model adds several key upgrades for enhanced reliability and magazine compatibility. The chamber body is precision CNC-machined from EN AW 7075 aircraft-grade aluminum. A standout feature is the adjustable magazine well height in 0.2 mm increments using stainless steel shims, helping to resolve feeding issues caused by poor magazine seating. After setting the correct height, it’s recommended to secure the threads with a drop of thread locker.The chamber inlet includes an O-ring to prevent BBs from falling out during reloads. A collet-style barrel nut ensures automatic barrel centering and eliminates movement during firing – compatible with inner barrels of 8.4–8.5 mm outer diameter. The PRO version features enhanced internal tolerances for improved BB feeding and is fully compatible with most hop-up buckings.

Comparison of BASIC, PRO, and ULTRA Hop-Up Chamber Models

BASICThe ideal option for players seeking a reliable and accurate chamber without extra tuning. Made from EN AW 7075 aluminum, includes an O-ring inlet and collet nut for barrel centering. Ready for R-hop and compatible with most buckings and inner barrels. Offers a great price-performance ratio and easy installation.
PROBased on the BASIC version, the PRO adds an adjustable magazine well height in 0.2 mm steps for better magazine compatibility with certain AR15 builds. It retains the collet nut, O-ring inlet, and CNC construction. Ideal for users who want reliability and fine-tuned feeding.
ULTRADesigned for advanced players who want a fully customizable chamber. Adds adjustable longitudinal positioning relative to the gearbox, along with an upgraded POM lock and clamping nut system that eliminates any barrel shift. Also features a flat, extended bucking channel compatible with ROBUST no-lip hop-up buckings. The ULTRA is RetroArm..