Brass cases Peterson .375 CheyTac

Peterson .375 CheyTac brass is premium, American-made Match-Grade cartridge brass designed for precision long-range and Extreme Long Range shooting. The cases are manufactured with tightly controlled dimensions, consistent internal capacity and a carefully engineered hardness gradient, providing the durability and repeatability expected by demanding ELR shooters.

Each box contains 50 new, unprimed cases with Large Rifle primer pockets and nominal 0.080 in flash holes. The cases are supplied with factory-annealed necks and shoulders.

Key product features

• Calibre: .375 CheyTac / 9.5×77 mm
• Manufacturer: Peterson Cartridge Company
• Manufacturer’s product code: 40021-R / 40021R
• UPC: 859449006056
• Quantity: 50 cases
• Case type: rimless, bottleneck
• Primer pocket: Large Rifle
• Nominal flash-hole diameter: 0.080 in / 2.03 mm
• Condition: new, unprimed brass
• Quality class: Match-Grade
• Country of manufacture: USA
• Factory annealed neck and shoulder
• Headstamp: “.375 (9.5x77)”

Large Rifle Magnum primers are commonly selected for cartridges of this capacity, but primer selection must always follow verified load data. The physical primer-pocket size is Large Rifle.

C.I.P. cartridge dimensions

The listed pressure is the C.I.P. standard limit, not a recommended load or reloading instruction.

Peterson reference-lot measurements

The following measurements were published for Peterson lot C178, inspected on 3 March 2025. They are reference values rather than guaranteed dimensions for every production lot.

Published measurements from other recent Peterson lots indicate an internal capacity of approximately 159–160 gr H₂O. Case weight, capacity, neck-wall thickness and annealing settings may vary between production lots. Reloading equipment should therefore be configured using measurements taken from the actual cases being loaded.

Why choose Peterson .375 CheyTac brass?

Peterson spent approximately 17 months and more than 1,000 working hours developing its CheyTac-calibre cases. The project reportedly involved 49 die and forming-stem iterations before the final production process was established.

The manufacturing process creates a controlled hardness gradient:

• a hard case head for strength and primer-pocket durability;
• controlled hardness through the case body;
• a softer, properly annealed neck and shoulder to support consistent bullet tension and repeated sizing.

Peterson also uses real-time statistical process control for 11 critical characteristics, including case and neck concentricity, shoulder position, overall length, primer-pocket dimensions, web thickness and neck-wall thickness.

In Peterson’s internal testing, individual cases reportedly reached as many as 15 reloads without sticking, neck splitting or case-head separation. This is a test result, not a guaranteed case life. Actual durability depends on chamber dimensions, pressure, sizing method, annealing procedure and the condition of the individual case.

Benefits reported by shooters

Users of Peterson CheyTac-calibre brass frequently praise:

• clean finishing and highly polished surfaces;
• consistent factory annealing;
• uniform flash holes;
• tight, consistent primer pockets;
• repeatable internal capacity;
• good neck-wall uniformity;
• strong case heads and long service life;
• minimal sorting required before initial preparation;
• high dimensional consistency for precision ELR ammunition.

Peterson .375 CheyTac brass is often regarded by experienced long-range shooters as one of the premium options available for this cartridge.

Chamber-fit and headspace information

The .375 CheyTac was used with numerous custom reamers and chamber designs before the publication of a formal C.I.P. specification. Peterson states that its cases were designed to fit chambers cut with PTG and JGS tooling as well as C.I.P.-dimensioned chambers.

However, older or custom rifles may differ from current C.I.P. dimensions. Some shooters have reported chamber and case combinations producing approximately 0.010 in of additional headspace. For this reason, case-to-chamber fit and headspace should be checked before firing, particularly in custom-built or older rifles and when changing brass production lots.

Peterson states that existing .375 CheyTac reloading dies can be used with these cases. Die adjustment should nevertheless be based on the rifle’s chamber and measurements from fired brass.

Preparation before first use

Before loading:

1. Inspect every case for damage or dimensional irregularities.
2. Measure case length, shoulder position and neck diameter.
3. Confirm proper headspace and chamber fit.
4. Check neck clearance with the intended chamber and loaded-cartridge dimensions.
5. Lightly chamfer or deburr the case mouth if required.
6. Develop loads only from reliable, current data and begin at the published starting charge.

Due to the very large case capacity and pressure involved, .375 CheyTac ammunition should be assembled only by experienced reloaders using suitable equipment and verified load data.