Got Gas Problems?

Gas checks are most useful on higher-pressure calibers like357 Magnum. Here, using
them made a big difference in accuracy (left.)

High pressures from maximum loadings and magnum cartridges can cause significant problems when coupled with cast lead bullets. Escaping gases can increase lead deposits in the barrel, unbalance the bullet and cause gun-damaging gas cutting. A solution to these problems is a gas check — a thin cup or disc made of copper, aluminum, zinc or brass and fitted to the base of a lead bullet to provide a harder base surface. It works as a seal to help prevent pressure from deforming the lead bullet and escaping around it.

Blocking the escaping gas not only minimizes the lead buildup and damage to the gun, but helps the bullet grip the rifling. There’s a fancy word for what the gas check helps the bullet do in creating the seal. It’s called obturation. To be clear, a gas check serves no purpose with copper-clad or other jacketed bullets.

Adding gas checks is easier than you might think. David runs them through a caliber-specific
sizing die, like this Lee Precision Sizing Die Kit.

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Gas checks are primarily used with lead bullets in high-pressure revolver cartridges like the .357 and .44 Magnums. They’re also helpful with .45 Colt rounds for self-defense or hunting and even 10mm semi-autos. Gas checks are available for the Enfield .303, M1 Carbine and other surplus rifle lead bullets, allowing you to reload and shoot affordable lead bullet cartridges. For calibers where ammo availability is limited, that can be a lifesaver.

There are several ways you can integrate gas checks into your reloading. One is to buy cast bullets with a gas check already installed. These are available from companies including Brownells, MidwayUSA, Grizzly Cartridge Company, Montana Bullet Works and Missouri Bullet Works. You can buy Hornady or Lyman gas checks and install your own if you’re casting your own bullets. Installing your own gas check is easy if you use a bullet sizing kit — I use a Lee Precision Lube & Size Kit for Cast Bullets. Pushing the bullets through the sizing die seats and crimps the gas check. Piece of cake.

Some hardcore handloaders make their own gas checks from beer cans or aluminum flashing, which is available at a building supply store. It takes some special tooling you may have to make yourself, but if you’re interested in making gas checks, there are some videos on YouTube showing you how.

David installed gas checks on these Polymer Coated .38 Caliber SWC bullets.

Pollution-Free Gas?

How well do they work? A good bore light will help you determine if the gas checks are helping keep your revolver’s bore clean. You can also check performance benefits by measuring a gas check’s effect on speed and accuracy.

I’ve been teaching reloading to one of my grandsons and his friend and one of our recent projects has been loading lead bullet cartridges with gas checks. Working with a Great Lakes Ammunition 158-gr. SWC polymer coated cast lead bullet, we installed Hornady gas checks using the Lee Precision Lube & Size Kit. We also loaded a batch of the exact same bullets without gas checks installed so we could compare results. For this load we used 3.0 grains of TiteGroup for both gas checked and non-gas checked bullets.

We chronographed both loads and found the gas checked bullets averaged 791 fps out of the chute and the non-gas checked bullets trucked along a little slower at 764 fps. Not really much difference there — a little over three percent. We also did some informal accuracy testing at 10 yards. The gas checked bullets grouped into 3″ while the non-gas-checked projectiles printed noticeably larger groups at 4.5″.

At the end of the day, my S&W 686 .357 Mangum wasn’t very dirty, and the holes in our targets were something we could smile about. If you’re casting your own bullets for .357 Magnum or .44 Magnum, adding gas checks is a surprisingly easy job using the Lee Precision bullet sizing kit for the appropriate caliber. For higher-pressure loads, you just might find yourself with a cleaner handgun and if you’re lucky, improved accuracy.

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