Hornady Lock-N-Load A Series Modified Cases - 300 Blackout (A300A)
- Caliber-Gauge:
- 300 AAC Blackout/Whisper
- Finish-Color:
- Brass
- Compatible With:
- Lock-N-Load Gauges
The Hornady Lock-N-Load A Series Modified Cases in 300 Blackout (A300A) are precision reloading accessories designed to work with Hornady's Lock-N-Load Precision gauges. If you're serious about handloading ammunition with tight tolerances—whether for subsonic hunting loads, suppressed shooting, or match-grade target rounds—these modified cases give you the measurement accuracy that separates consistent loads from guesswork. The 300 Blackout's popularity for both short-range hunting and precision shooting makes reliable case preparation essential, and these inserts let you verify bullet seating depth and overall cartridge dimensions with confidence.
Each A300A case is specially modified with precision fine threads that lock securely into your gauge, keeping the case perfectly square and aligned—no wobble, no guessing where the chamber will actually sit. The neck is opened and shaped to allow standard-diameter bullets to enter concentrically, meaning your bullet seats straight without binding or cocking. That concentricity matters: it's the difference between a load that chambers smoothly and one that headspaces unpredictably.
These aren't loaded ammunition or complete reloading dies; they're reference tools for the reloading bench. Use them with your Lock-N-Load dial calipers, OAL (overall length) gauges, or other precision measuring equipment to verify that your finished rounds match your specifications before you fire them. For handloaders who take pride in consistency—or who need it for hunting, competition, or subsonic loads—this is a straightforward way to add a quality control step that pays dividends downrange.
Key Features
- Modified case body with precision fine-thread attachment for Lock-N-Load gauges
- Perfectly round, opened neck for concentric bullet insertion
- Square alignment in gauge ensures accurate chamber positioning reference
- Caliber-specific design for 300 Blackout
- Works with Hornady Lock-N-Load Precision gauge systems
Specifications
| Caliber | 300 Blackout |
| Product Type | Modified Case Insert (Measurement Tool) |
| Brand | Hornady |
| Model | A300A |
| Compatibility | Hornady Lock-N-Load Precision Gauges |
Frequently Asked Questions
What gauges work with the 300 Blackout A Series modified case?
This insert is designed to work with Hornady Lock-N-Load Precision gauges. Confirm your specific gauge model is compatible with the Lock-N-Load system before purchase.
Is the dial caliper or OAL gauge included?
No. This product is the modified case insert only. Measuring tools like dial calipers and OAL gauges are sold separately.
Can I use this for subsonic 300 Blackout loads?
Yes. This modified case works as a reference tool for any 300 Blackout load, including subsonic hunting and target rounds. It helps ensure your finished ammunition meets your specifications before firing.
How does this improve my reloading accuracy?
The concentrically shaped neck allows bullets to seat straight without canting, and the fine-threaded attachment keeps the case perfectly square in your gauge. This lets you measure overall length and bullet seating depth precisely, so every round you produce is consistent.

