I’ve always considered the primary purpose of gas checks to be the prevention of “leading” – leaving traces of lead in the bores of my guns. Leading makes a gun inaccurate and can theoretically cause pressure problems if it gets bad enough. It can be a real pain to clean out too. I’ve never really thought about gas checks helping to prevent airborne lead emissions, but I suppose it’s possible.
Yes, gas checks do protect the base of the bullet from the burning propellent. That’s one theory, amongst many, as to how they help prevent leading. 1000fps with a relatively soft, non-gas check type cast lead bullet is probably a good upper limit. But if you get the right amount of tin and antimony in your alloy, cast at the right temperature, size your bullets to the right size for your guns bore, and use the right lube, your cast bullets won’t lead even if they’re not gas check types up to around 1500fps. I’ve also found that .38s (.357s) are more prone to leading than .41 and larger calibers.
When I said I’d become too lazy to cast my own gas check type bullets anymore that was only partially true. I really don’t like messing around with gas checks. They’re small and easy to drop with my fumbling fingers. And they often don’t fit right – they’re either so tight I have to use a lot of pressure to force them on, or they’re so loose they fall off – even the Hornady so called “crimp on” types.
For someone just getting into reloading you’re certainly enthusiastic. I’m not sure I’d try to start casting my own handgun bullets just yet – especially not gas check types. While it’s not rocket science, there’s a lot of equipment involved. You’ll need not only a mold and handles, but you’ll also need access to good alloy, a way to melt the alloy and a place to do it, and a lubricator sizer with the right sizing die. It’s just like when you bought your reloading equipment – the initial outlay of cash can be pretty nasty. Then again, there’s nothing quite like having ammo you built yourself, including the bullets, perform perfectly.