The Forster 30-40 Krag No-Go Gauge (brand part no. BG3040N) is a precision steel headspace gauge that flags a 30-40 Krag chamber cut too deep during barrel fitting. Forster Products machines it to a fixed 1.19-inch length marking the upper edge of acceptable new-build headspace; if the bolt closes easily on this gauge, the chamber needs correction before the rifle is put into service. Used together with a go gauge, it brackets the safe headspace range for this older military chambering during a rebarrel or repair job. It’s a solid addition to the rest of our gunsmithing tools and gunsmith supplies for anyone working on Krag-Jorgensen actions.

Key Specifications

• 30-40 Krag Chambering Ground to the exact maximum headspace dimension for the 30-40 Krag cartridge.
• No-Go Gauge Type Marks the maximum acceptable headspace for a properly finished new chamber.
• 1.19-Inch Gauge Length A fixed, precision-ground reference length for a consistent go/no-go reading.
• Steel Construction Hardened steel built to hold its critical dimension through repeated checks.
• Single-Piece Gauge Sold individually for use alongside a go gauge during chamber inspection.

Frequently Asked Questions

What happens if the bolt closes on this gauge during a rebarrel? It indicates the chamber was reamed too deep and the barrel work needs to be corrected before the rifle is safe to fire.

Is this the right gauge for checking an old, well-used Krag? A field gauge is the more appropriate tool for evaluating wear on a rifle already in service; this no-go gauge is meant for new-build verification.

Buy the Forster 30-40 Krag No-Go Gauge, Steel

Bracketing headspace correctly on a Krag rebarrel job protects both the rifle and the shooter. Order this no-go gauge from our Lubbock, Texas gun shop for fast, insured shipping to your bench.