I Own Guns

Bullet Casting Basics: Gas Check Bullets Without a Gas Check

Written on October 20, 2013   By   in Bullet casting

I think just about everybody who has considered casting bullets has at some point pondered whether they could shoot cast lead bullets designed to use a gas-check without one. I know I did.

I don’t have scientific data to give you on the subject, just the results of some testing that I performed so that I would know for myself.

The testing I performed consisted of firing up to 100 rounds each of 3 different bullet designs. All of the designs were known to be accurate in the guns that I was testing in. The alloy was the same as what I normally use for the bullets with the GC in place. Each design was tested loaded to several levels. All loads were within book loading data. The loads ranged from roughly 800 FPS up.

I was looking for 2 things when assessing the loads; Accuracy and Leading. All bullets were sized and lubed using the same sizing dies and lube as they would have been if wearing a gas check (usually .001 or .002 over groove diameter, depending on what the throat would allow). None of the loads produce any leading when used with a gas check, and all have proven at least reasonably accurate when using a gas check as well.

Rather than boring you with all of the details, since my results were the same across the board with each of the 3 designs tested, I’ll simple say this: All of my experimentation leads me to believe that 1100 FPS is about as hard as I am able to push a gas check bullet without a gas check before I see accuracy drop off, or leading start. If accuracy fell off, I made a note of it and pushed on. If leading started, I ended the experiment. Each design saw failure in one area or the other somewhere between 1100 and 1200 FPS. The loads that lost accuracy continued to be pushed to see if accuracy was re-acquired with more pressure. In all cases leading started by about the 1400 FPS threshold. None of the loads regained accuracy before starting to lead.

Please don’t take that as gospel, as I said, my experiment was far from scientific, and any number of variables could have changed the outcome. A harder alloy might have gained me some velocity, a different lube might have allowed me to push them harder, etc. etc. etc.

What my experiment told me was that it’s worth trying a gas-check design of bullet without the check for a low powered load. It might not pan out, but there’s a good chance that it could. If I feel like I’m going to want to push a bullet over about 1000 FPS though, I am likely to either use a gas check on the design, or start with a plain based design. I have had success pushing plain based bullets to velocities as high as 1500 FPS without loosing accuracy or seeing any leading. I assume that some of the reason for that is the thickness of the base driving band on the plain based bullets. Generally the wider the base driving band is, the harder I can push the bullet before I start to see leading or a loss of accuracy.

If you have experience with this, please let me know how things worked for you!