Peterson 300 Win Mag – Long – 25 ct

The Peterson Win Mag Long is a clever 25 count box of 300 Winchester Magnum brass that headspaces off the shoulder instead of the belt, and choosing the Peterson Win Mag Long can dramatically extend how many times you reload each case. Made by Peterson Cartridge of Pittsburgh, it is a smart answer to a long standing 300 Win Mag reloading problem. If you handload the 300 Win Mag and want more case life, this is the brass to study.

What The Peterson Win Mag Long Is and Who It Is For

Peterson produces its 300 Winchester Magnum brass in two versions, the traditional SAAMI spec case that headspaces off the belt and a version that headspaces off the shoulder, which Peterson calls the 300 Win Mag Long. Traditional 300 Win Mag cases tend to show case head separation after only five to seven firings, because the SAAMI dimensions can leave extra room between the case shoulder and the chamber. This brass is for the handloader who is tired of losing cases early and wants more reloads per piece.

If your rifle chamber allows it, the Peterson Win Mag Long lets the shoulder do the headspacing so the case works less and lasts longer.

Key Features of This Brass

• Twenty five pieces of Peterson 300 Win Mag brass in the Long configuration.
• Headspaces off the shoulder rather than the belt for extended case life.
• Engineered to fight the case head separation common to traditional 300 Win Mag brass.
• Match grade construction from a maker focused on precision brass.
• Uniform case walls and necks that promote even neck tension.
• Reloadable brass ready for careful load development.

Specifications Worth Knowing

Each box holds 25 rounds of new, unprimed 300 Winchester Magnum brass in the Long, shoulder headspacing design. The concept addresses a quirk of the 300 Win Mag, where the SAAMI tolerance stack can place the shoulder well short of the chamber wall, stretching the case and causing early separation. By headspacing off the shoulder, this brass reduces that stretch and can meaningfully increase reload count. This is component brass, not loaded ammunition, so you supply the primers, powder, and .308 bullets.

Practical Use, Care, and Compatibility

Confirm your chamber suits shoulder headspacing, then fire form, size to your chamber, and trim to length. Managed this way, the Peterson Win Mag Long can outlast traditional brass by a wide margin, saving you money over time. It fits rifles correctly chambered for the 300 Winchester Magnum. Complete your magnum reloading bench with dies and components from our Apparel and Gear collection.

More Reloads from Your 300 Win Mag

Anyone who has reloaded the 300 Winchester Magnum knows the frustration of losing cases to early head separation. The traditional belted design lets the case stretch on each firing, and after only a handful of cycles the brass is done. The Long design attacks that problem at its root by letting the shoulder control headspace.

For a high volume shooter, more reloads per case means real money saved over the life of a rifle.

Load Development and Long Term Value

To get the benefit, fire form the brass in your chamber, then set your sizing die to bump the shoulder just enough for reliable chambering without overworking it. Keep firings logged so you can see how much longer these cases last compared to standard belted brass.

Managed this way, a box of twenty five can outlast several boxes of traditional brass, which is exactly the return that makes the Long design worth choosing.

Ordering and Storage

Store your twenty five cases in a dry, labeled box and keep firing records so you can prove out just how much longer the Long design lasts. Clean, dry brass keeps for years, letting you fire form and develop loads at your own pace as you stretch every case to its full potential.

For the 300 Win Mag handloader who wants more reloads, the Peterson Win Mag Long is a genuine upgrade. Ships direct to your door, no FFL required.