The Hornady Lock-N-Load Modified Case, B Series .300 Rem Ultra Mag (Hornady part no. B300) is a specially prepared .300 Rem Ultra Mag case built to work with Hornady Lock-N-Load Precision gauges rather than being loaded and fired like standard brass. A fine thread at the case head lets it screw onto the gauge and stay perfectly square for an accurate reading. The neck is machined perfectly round and opened slightly beyond standard dimension so a bullet slips in smoothly and concentrically, which keeps the gauge measurement honest. Anyone measuring headspace on .300 Rem Ultra Mag needs the case that matches the chamber, and this is it.

Key Specifications

• This modified case is prepared specifically for .300 Rem Ultra Mag, matching your chamber for an accurate gauge reading.
• A fine thread at the case head lets it screw onto a Lock-N-Load Precision gauge and stay square during use.
• The neck is machined perfectly round for consistent, repeatable gauge readings.
• The neck is opened to a .002-inch oversized diameter so a bullet slips in smoothly and concentrically.
• It is part of Hornady’s B Series of interchangeable modified cases covering common chamberings.

Frequently Asked Questions

Can I load and fire this .300 Rem Ultra Mag modified case like normal brass? No. It is built specifically to thread onto a Lock-N-Load Precision gauge, not to be loaded and fired.

Why is the case neck oversized? The .002-inch oversized, perfectly round neck lets a bullet slip in smoothly and concentrically for an accurate gauge reading.

Buy the Hornady Lock-N-Load Modified Case, B Series .300 Rem Ultra Mag

Order today and it ships fast from our Lubbock, TX gun shop. Find the Hornady Lock-N-Load Modified Case, B Series .300 Rem Ultra Mag in Hornady‘s reloading equipment lineup and get an accurate .300 Rem Ultra Mag gauge reading on your next batch.