300 Blackout Brass: New vs. Converted vs. Once‑Fired — Which Should You Buy?

300 Blackout Brass: New vs. Converted vs. Once‑Fired — Which Should You Buy?

A Practical Buyer’s Guide for Reloaders in 2025

300 Blackout remains one of the most adaptable AR‑15 calibers, and demand for quality brass is consistently high. Whether you’re loading subsonic rounds for suppressed shooting or supersonic loads for hunting, or plinking the brass you choose affects reliability, consistency, and case life.

Reloaders often compare new brass, converted brass, and once‑fired brass — and each option serves a different purpose. This guide breaks down the differences so you can choose the best brass for your rifle and your reloading goals.

What Is the Difference Between New, Converted, and Once‑Fired 300 Blackout Brass?

Factory‑New 300 Blackout Brass

New brass is manufactured specifically for 300 BLK. Brands like Starline, Hornady, and Nosler produce highly consistent cases with uniform necks, primer pockets, and case walls.

Pros

• Maximum consistency
• Longest case life
• Ideal for tuned or hunting loads
• Zero prep work
• Uniform headstamps

Cons

• Higher cost
• Sometimes harder to find in bulk

Converted .223/5.56 Brass

Converted brass begins as .223 or 5.56 cases that are cut, formed, and resized into 300 BLK. Many reloaders convert their own, while others buy pre‑processed brass.

Pros

• Lowest cost per piece
• Easy to find in bulk
• Lake City brass is especially durable
• Great for subsonic and training loads

Cons

• Quality varies depending on who processes it
• Neck thickness can vary if not trimmed correctly
• Slightly shorter case life
• Cost of tools and the time performing the cutting and resizing

Once‑Fired 300 Blackout Brass

This is a high‑value middle ground — real 300 BLK brass that has been fired once, inspected, cleaned, and often resized and trimmed.

This category is extremely popular with reloaders because it offers the reliability of factory brass at a much lower cost.

Pros

• True 300 BLK brass (no conversion stresses)
• More affordable than new brass
• Longer case life than converted brass
• Great for bulk loading, hunting, and general use
• Often comes fully processed and ready to load
• Consistent headstamps when sourced properly

Cons

• Availability varies
• Needs inspection like any used brass

Why reloaders love it:
Once‑fired brass gives shooters 90% of the performance of new brass at 50–70% of the cost, making it one of the best values in the 300 BLK world. For many reloaders, it’s the “sweet spot” between cost and performance.

Which Should You Buy? A Practical Breakdown

Choose New Brass If You Want:

• Maximum consistency
• Longest case life
• Premium hunting or tuned loads
• Uniform headstamps

Choose Converted Brass If You Want:

• The lowest cost per round
• Bulk quantities for training
• Brass for subsonic loads
• A budget‑friendly option

Choose Once‑Fired Brass If You Want:

• The best balance of cost and performance
• True 300 BLK brass without conversion
• Longer life than converted brass
• A reliable, affordable option for most reloaders

Performance Notes from the Reloading Community

Reloaders consistently report that:

• New brass offers the most uniformity.
• Converted Lake City brass performs extremely well when processed correctly.
• Once‑fired brass is the best value for most shooters, offering excellent reliability and long case life at a lower price.