Building the 7mm Sherman Mega: Sub-MOA Out of the Gate

Gavin Gear of Ultimate Reloader takes on a new wildcat in this build video, chambering a rifle for the 7mm Sherman Mega, a cartridge based on the 300 Norma shoulder blown out and necked to 7mm to push serious velocity in a long-action platform. The video walks through the full gunsmithing process and ends with the rifle producing sub-half-MOA groups straight out of a published load, no load development required.

Key points

• The parts list: a BAT Igniter Long Action, Foundation Samson XT long-action stock, a 27-inch Guesley barrel blank in 1:8 twist, a TriggerTech Diamond two-stage trigger, and Hawkins M5 long-action bottom metal.
• Software-guided machining: Gear uses Rifle Builder Pro with a custom 7mm Mega chamber profile to handle pre-drill, tenon, thread relief, chambering and muzzle threading calculations on a PM 1440 lathe.
• Tooling notes: a piloted Manson reamer and go gauge get the chamber dialed in, and Sherman Wildcats supplied a custom Hornady die set for sizing and seating.
• Range results: using a Sherman Wildcats load of N565 behind a 180-grain Berger, the rifle shot a three-shot group under 0.3 inch and a five-shot group around half MOA, with average velocity over 3,100 fps.
• Still rough edges: standard deviations climbed across groups, which Gear says points to more load tuning ahead despite the strong initial accuracy.

Quick take

This is less a review of a finished product and more a documented proof of concept, and it's a convincing one. Ultimate Reloader shows that a well-chosen wildcat, quality components, and a published load can produce serious accuracy before any real load development begins. Anyone building a long-range 7mm will want to see the full process.

Watch the full video: Ultimate Reloader