The RCBS Chamber/Cartridge Length Gauge for .300 AAC Blackout (RCBS part no. 88282) does double duty for handloaders running this popular AR-platform cartridge: drop a finished round in and it checks both chambering fit and overall cartridge length in a single step. Because .300 Blackout is loaded across such a wide bullet-weight range, from light supersonic loads to heavy subsonic rounds, verifying case and cartridge dimensions before a trip to the range matters more than with most calibers. This gauge gives reloaders a fast, repeatable way to confirm a batch is safe to feed and fire.

Key Specifications

• Purpose-built for the .300 AAC Blackout cartridge, matching its specific chamber and case-length dimensions.
• Checks chambering fit and cartridge length together, so one drop-in test covers two critical safety checks.
• Covered by RCBS’s Limited Lifetime Warranty for long-term bench use.
• Compact and travel-friendly at roughly 0.28 lb, easy to keep in a range bag alongside loaded ammunition.

Frequently Asked Questions

Why does .300 Blackout benefit from this kind of gauge? The cartridge is loaded with a wide range of bullet weights and seating depths, so confirming cartridge length and chamber fit before firing helps avoid feeding issues in AR-platform rifles.

Does this replace a case trimmer? No, it’s a verification tool. Trim and resize cases first, then use this gauge to confirm the finished round is within spec.

Buy the RCBS Chamber/Cartridge Length Gauge .300 AAC Blackout

Keep every batch of handloaded .300 Blackout ammunition checked and consistent with this RCBS gauge on the bench. See more from RCBS in our case prep supplies selection. Order it from our Lubbock, Texas gun shop for fast, reliable shipping.