What is a Gas Check

A gas check is a small piece of metal added to the base of some cast lead bullets to prevent the propellant gas leakage that causes gas cutting and to help the bullet grip the rifling in the barrel.

Gas checks are made of several different materials. Some of the more common materials include aluminum, copper and brass.

Gas checks are applied on the bullet typically during the sizing process. Many sizing dies or lube sizer type devices include the means to add these gas checks. Gas checks are designed to crimp onto the base of the bullet.

Additional information on gas checks is available on Wikipedia.


What Size Gas Check?

What size gas check do I need? Well we can help you with that. Typically the first thing we need to do is figure out what caliber check we need. Here is a list of common calibers and what size check they use.


22 Caliber: 22 Caliber Bullets

7mm: 270 Caliber, 6.5mm/264, and 7mm/284 Bullets

30 Caliber: 30 Caliber, 7.62x39, 303 British Bullets

35 Caliber: 35 Remington, 38 Special, 357 Magnum, and 357 Maxim Bullets

44 Caliber: 44 Magnum, 44 Special, and 454 Bullets

45 Caliber: 44/454, 45/454, and 458 Bullets

50 Caliber: 500 S&W Bullets


After we determine what caliber of check is needed, we can figure out the material thickness. In order to figure out material thickness, use the calculator to the right. Enter the sized bullet diameter and enter the shank diameter at the base of the bullet (where the gas check goes). After clicking get results you will get the thickness of the material needed.

In case you were wondering the following formula is used to determine gas check thickness:

T = (Sd - SHd) / 2

T = Material thickness required.

Sd = The Bullet Final sized diameter

SHd = The Bullet Gas Check Shank Diameter


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Gas Check Size Calculator