SKU: 5551764002

PETERSON BRASS 300 WIN MAG - LONG (50 PK)

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Description

PETERSON BRASS 300 WIN MAG - LONG (50 PK)Get more reloads on your . 300 Win Mag casings with Peterson's . 300 Win Mag Long. If you are a handloader that wants more reloads from your . 300 Win Mag casings, then you're going to love Peterson . 300 Win Mag Long casings. The regular . 300 Win Mag casing Peterson makes is the traditional SAAMI specd version that headspaces off the belt. This longer casing version different is different however, as it headspaces off the shoulder. Traditional . 300

Get more reloads on your .300 Win Mag casings with Peterson's .300 Win Mag – Long. 
If you are a handloader that wants more reloads from your .300 Win Mag casings, then you're going to love Peterson .300 Win Mag - Long casings. 

The regular .300 Win Mag casing Peterson makes is the traditional SAAMI spec’d version that headspaces off the belt. This longer casing version different is different however, as it headspaces off the shoulder.  

Traditional .300 Win Mag casings tend to show signs of case head separation after only 5 to 7 firings. This is because SAAMI specs for any calibre, list a minimum and a maximum tolerance for each dimension on the casing and the rifle’s chamber. With most calibers, the max dimension of the casing for length-to-shoulder (L-T-S) has the shoulder of the casing right up against the chamber wall. 

With a .300 Win Mag, unlike most other calibers, if your rifle’s chamber is cut to the SAAMI minimum for L-T-S, and your casing is at the max length-to-shoulder dimension, the casing shoulder is still .0095” away from the chamber wall. With the same minimum rifle chamber, a casing at nominal L-T-S is .012” away from the chamber wall. In a worst-case scenario, if the casing was produced at the SAAMI minimum L-T-S, and the chamber was cut at the maximum L-T-S dimension, the casing shoulder could be up to .026” away from the chamber wall. This is actually quite a a lot.
That large gap is what causes the casing to stretch so much when it is fired. And it’s that stretching that causes premature case head separation.

These .300 Win Mag- Long casings are made with a longer L-T-S dimension. (All the other dimensions are SAAMI spec.) Its longer L-T-S is what prevents the casing from stretching excessively on the 1st firing. The casing gets more support, which means less stretching and ultimately, a longer case life.

 

Additional Information

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.

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Exchange/Return Notes
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SKU: 5551764002

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tjw
Whiting, US
★★★★★ 3
Way too narrow
Size: 9.5 Wide, Color: Burgundy Polished Full Grain
I ordered a wide in this shoe, but it was still way too narrow. I had to return them. Otherwise, it looked like a nice quality shoe.
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Reviewed in the United States on February 12, 2026
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BetterEveryDay
San Leandro, US
★★★★★ 5
I usually wear 11.5's, but I buy 1/2 size smaller to accommodate for stretch. Leather relaxes.
Size: 11, Color: Burgundy Polished Full Grain
5 STARS: These shoes are awesome. I keep coming back for more. I have major foot problems, have tried all kinds of shoes, orthotics, and inserts... but believe it or not, these shoes work better than any of that stuff. I wear them daily. I buy lots of them, for home, for church, and I'm getting my first pair of J&M boots today, for winters in Indiana... Brrrr
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Reviewed in the United States on December 18, 2025
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Doc
Battle Creek, US
★★★★★ 5
Great price great shoe
Size: 12, Color: Burgundy Polished Full Grain
Excellent shoe. Tried the Sebago penny loafer and the sizing was ridiculous. These J and M are sized perfectly. I’ve had them before and they wear like iron. Very comfortable right out of the box.
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Reviewed in the United States on May 23, 2026
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roger mendes
Grantham, US
★★★★★ 5
One of the best shoes
Size: 9.5, Color: Black Polished Full Grain
Outstanding. Fashionable, most comfortable and good construction. No sines of use after quite some time. Highly recommended.
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Reviewed in the United States on March 21, 2026
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xyz
Whiting, US
★★★★★ 4
Quality shoe but with a slight squeak.
Size: 10 Wide, Color: Burgundy Polished Full Grain
Nice shoes with the classic Penny Loafer design. Fit was better than another brand I tried. Only reason not 5 starts is disappointment due to a slight squeak at times when walking.
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Reviewed in the United States on August 11, 2025

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