Peterson Brass 300 Winchester Mag Unprimed Box of 50

300 Winchester Magnum

All Peterson Cartridge casings come in one of their plastic ammo boxes. 

Made in the U.S.A.

Peterson makes the traditional SAAMI spec’d version that headspaces off the belt. But it also makes a version that headspaces off the shoulder. Peterson calls that version the .300 Win Mag- Long. This listing is the SAAMI spec version.

“I am extremely pleased to announce that as of July 20th, 2020, Peterson Cartridge has now added .300 Winchester Magnum brass to its’ product line,” stated president, Derek Peterson. “The road for us to produce this belted magnum case has been long, frustrating, and expensive. It has taken us over three years to release this cartridge and cost us well over $50,000 in experimental tooling alone.”

Peterson continued, “Producing a brass casing with a really good belt is a difficult thing. Getting the tooling just right is an iterative process, and these .300 Win Mags took more iterations than I care to remember.

“To make a new caliber casing for the first time, we design and order all the tooling. After it arrives, we do what we call a proof-of-concept (p-o-c) run. With most of the 30+ new tool packs we’ve designed, we end up with a “Best Vision” casing after one or two iterations.

“But these .300 Win Mags! With many of the p-o-c runs, the resultant belt wasn’t crisp enough. So we would redesign and order different tooling and try again. With some runs we’d get a good belt, but it wasn’t in the exact correct location. Some runs, the belt was good and in the correct location, but the equipment wouldn’t run it efficiently or the scrap rate was too high. It took a few different tooling iterations to get the grain structure in the casing walls just right. After some of the failed iterations we would speculate, maybe the problem is with the dimensions of the brass cups we are using as raw material. So, we’d redesign those, and try again.

“But after three years of unsettling self-doubt, and countless iterations WE GOT THE BELT. We can now make belted magnum casings! And we have really good .300 Win Mag casings on the shelf, with as good a belt as any in the industry. Our ballistician has shot some of these 20 times in a row, at SAAMI max pressure, with a minimum shoulder resize and they are still holding up well.”

Peterson concluded, “If you are one of the many customers who’ve called us every week to say, “When are you people ever going to release .300 Win Mag,” we have two responses. First, thank you for waiting. Second, FINALLY, here you go; we got the belt!”

Warning: Only use Peterson Cartridge Co. casings in firearms in good condition, designed, marked, and chambered for this cartridge. Do not use Peterson Cartridge Co casings for “fire forming” or any other purpose other than what they were designed and tested for. Peterson retains no responsibility for the enclosed casings if they are used outside of the manufacturer’s recommendations.

This is not loaded ammunition.