GSI 300 AAC Blackout Trim Die System
300 BLK Conversion with GSI's 300 AAC Blackout Trim Die System

For more than 10 years GSI International has been creating products for the firearms industry that are up to snuff in every way possible.

One of the company’s newest products is the GSI 300 AAC Blackout Trim Die System

The system is made up of two separate dies: The rough trim die and the trim die. They are designed to be used with the Dillon RT1200B or RT1500 trimmer motors, and specifically designed to be used progressively with the GSI Trimmer Toolhead.

The rough trim die is an intermediate size/trim step between 5.56×45 NATO or .223 Remington and 300 AAC Blackout.

It was GSI’s experience during development that if it used a traditional trim die for the conversion process alone, that the brass was not supported properly when it first contacts the trimmer. This caused the case to spin with the trimmer creating a jam. The roughing die is the proper size to grip the case before it ever contacts the trimmer, allowing for an excellent roughing cut. Being that it is a rough cut, there is no need for fine adjustment.

The trim die is a traditional full length sizing die, manufactured to minimum tolerance. It is designed to be used after the rough trim die, or with once fired brass, for final size and trimming.

Both the rough trim die and trim die are hardened steel dies that require the use of case lube.

For more information on the 300 AAC Blackout Trim Die System and other products from GSI International, please visit

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