The EGW .300 Blackout 7-Hole Cartridge Checker is a precision measuring tool for handloaders and shooters who run .300 Blackout through AR platforms or bolt guns. Before you chamber a round—whether factory or handloaded—this aluminum case gauge lets you verify that your ammo actually fits your rifle's chamber. Out-of-spec rounds cause feeding issues, jams, and worse. A few seconds with this checker catches problems before they happen downrange.
Built from solid 6061-T6 aircraft-grade aluminum and machined with actual Clymer reamers, this tool matches the real geometry of a .300 Blackout chamber. The seven-hole design lets you quickly check multiple rounds. You'll measure both the minimum case diameter and maximum overall length—the two critical dimensions that determine whether a cartridge will chamber safely and reliably. Anodized matte black finish stands up to shop use.
If you're serious about reloading .300 Blackout or evaluating factory ammo before trust-loading it into your gun, this is the kind of practical insurance that prevents range frustration and keeps your equipment safe. It works with any .300 Blackout rifle.
Key Features
- Seven-hole design for quick batch checking
- Machined from solid 6061-T6 aircraft-grade aluminum
- Actual Clymer reamers ensure true chamber geometry
- Checks minimum case diameter and maximum overall length
- Anodized matte black finish
- Works with factory ammunition and handloads
Specifications
| Caliber | .300 Blackout |
| Checker Type | 7-Hole Cartridge Checker |
| Material | 6061-T6 Aircraft-Grade Aluminum |
| Reamer Type | Clymer |
| Finish | Anodized Matte Black |
Frequently Asked Questions
How do I use a cartridge checker?
Simply insert a loaded round into each of the seven holes. If the cartridge fits completely into the hole, it's within spec for your chamber. If it's too long or the case diameter is too large, the round won't fully seat, signaling an out-of-spec condition.
Can I use this with factory ammunition?
Yes. This checker works with both factory and handloaded .300 Blackout ammunition. It's an effective way to verify that any ammunition you're about to shoot meets chamber specifications.
What makes this different from other case gauges?
This EGW checker is machined from solid 6061-T6 aircraft aluminum and uses actual Clymer reamers, ensuring the gauge matches true .300 Blackout chamber geometry rather than approximating it.
Will this fit my .300 Blackout rifle?
This gauges .300 Blackout ammunition only. It verifies whether your loaded cartridges will chamber safely in any .300 Blackout rifle.
