A Gas Check is a disc at the base of the projectile used in the construction of certain types of bullets, primarily those made of lead.
The primary function of gas checks are to reduce barrel fouling and enhance bullet performance when fired at higher velocities and are usually only necessary on very high-pressure rounds that have a soft-lead projectile.
Here's an in-depth look at gas checks:
Basic Definition
A gas check is a small, cup-shaped piece, typically made of copper or a similar metal, that is affixed to the base of a lead bullet.
Purpose and Function
Reduce Barrel Fouling
When lead bullets are fired at high velocities, they can leave behind lead deposits in the rifling of the firearm's barrel, a phenomenon known as "leading."
This fouling can degrade accuracy over time. A gas check acts as a barrier between the hot gases and the base of the bullet, reducing this leading.
Enhance Bullet Performance
Gas checks can allow lead bullets to be loaded to higher velocities than they typically would without causing excessive fouling or bullet deformation.
Pressure Seal
As the cartridge is fired, the gas check can also help to create a seal in the bore, ensuring consistent gas pressures and improving bullet stability and accuracy.
Application
Gas checks are often used with cast lead bullets, especially in rifle cartridges. While many pistol velocities are low enough that leading isn't a significant issue, rifle velocities can often benefit from the addition of a gas check.
To apply a gas check, the bullet must be designed with a specific shank or heel at its base to accommodate it. Once the gas check is placed on the bullet base, it's often crimped in place during the bullet sizing process.
Considerations for Reloaders
Handloaders who cast their own bullets from lead often employ gas checks when loading for higher velocities or when using certain types of powders that may exacerbate leading.
While gas checks can mitigate leading, they also add an additional component and step to the bullet-making process, which can be a consideration for reloaders in terms of time and cost.
Alternative Solutions
Besides gas checks, there are other solutions to reduce leading, such as using harder lead alloys, adding a polymer or powder coating to the bullet, or using jacketed bullets.
In summary, in the shooting sports world, a gas check is a practical solution for those wanting to achieve higher velocities with lead bullets without the drawbacks of excessive barrel fouling.
Especially relevant for handloaders and those casting their own bullets, gas checks enhance bullet performance while ensuring the longevity and accuracy of the firearm.
