Keep seeing the reference to 'gas check' ? And what's the benefit ?

Can't help ya here. To me, it only means, "Am I using diesel or unleaded??"

It's a copper cover that crimps over the bottom of a cast bullet to prevent cutting or scoring on the bottom from the hot gasses when it is fired.

LOL...me too.

Good quick explanation:

http://en.wikipedia.org/wiki/Gas_check

Is it really that critical , JB ?

Perfect...thanks. Didn't even dawn on me to Google the damn term. Thanks again.

Depends upon the specific lead alloy being used and velocity. Once you've scrubbed a badly leaded barrel a time or two, the criticality of the gas check in certain situations becomes apparent.

Thanks, Stush...give's me some material to work with.

depends on the gun and load too, and like stush said the material makes a difference. The softer the lead alloy the more prone it is to deformation. There is a school of thought that not using them causes them to act kind of like the hollow base conicals used in civil war muskets. I run all gas checks in my big mags but my 44 spcl I'm running a Cast Performance 255gr plain base and it's the most accurate bullet for that gun running on top of a full case of H110

Rod/Stush, is it something that really bears considering ? I guess what I mean is if I'm shooting hard casts ; should they be 'gas check' ? Or am I talking two different animals here ?

try them both, the gas check also is supposed help seal the bullet in the barrel like a copper jacket and reduce leading but I'd decide on a bullet weight you want try and then get a box of each. CP offers most of their bullets in both and the difference in weight is only 5gr. I like CP and Trueshots from Oregon trail are my favorite as they have the hardest bullets on the market that I know with a Brinnel hardness of 24, most others are 21-22 which is still plenty hard. The biggest reason I like them is because I can crank them up in my rifles without leading issues. There was another post last week and alot of the guys like Beartooth and I know Dan B. likes the Penn bullets. I have no experience with Beartooth and I've only shot a handfull of 405gr Penns in my 45LC's so I couldn't give a good review one way or the other.

rapptor, "diesel or unleaded"....excellent

It does not come into play unless your molds are of gc type. Shooting gc type bullets without gc installed are irratic,spelling?, in most of my guns. Gc's are needed to seal and may prevent leading. I use them in rifles and contender calibers such as 30 herrett. They are essential in my 308, 6 mm, others. Without them, I have serious leading and terrible flyers. They are getting hard to find and expensive, making casting almost too expensive! That is ehy all my Shilohs and rolling blocks shoot a non-gc bullet.

With speeds below 1500 ftps or so and a decently hard bullet you can get by without them .Push it harder and/or softer bullet and may get leading. Each barrel and firearm are different and some will lead at lower velocity than others,or shoot better with one over the other . Trying a few of both is the only way to know with your gun.

Appreciate it,fellas. Great info.