View Full Version : Seating gas checks????

January 7, 2010, 11:44 AM
I have an RCBS Lube-a-matic 2 and bought the Lyman gas check seater. It was advertised to fit the Lyman presses as well as the Lube-a-matic. When I got it, I found out it only fit the original Lube-a-matic, NOT the "2." I confirmed this by calling Lyman. There is currently NO gas check seater to fit that press.

So, how are you all seating gas checks?

January 7, 2010, 12:06 PM
Mac, I always heard there was such a thing as a gas check seater. I never found out how it worked or what it looked like. The reason is, just putting the gas check on the base of a bullet made to take one, then sizing and lubing it seated the gas check just fine. In other words, it's not needed.

I'll add this in case someone else see's this, even though you probably already know it. You can't just put a gas check on just any cast bullet. The mold and bullet has to be made to take a gas check. There's a rebated heel on the very bottom of a bullet made to take a gas check.

Gas checks sold today are all made by Hornady. They're made to crimp on the rebated portion of the cast bullet. Take a close look at the gas check, a 10X magnifier will show you the inside edge at the top is a little thicker than the rest of the check. It is sized into the heel to dig into and hold the check on.

Lyman used to make a brass gas check that was a simple cup. They were notorious for falling off when fired. The Lyman checks sold today are made by Hornady, repackaged by Lyman.

January 7, 2010, 03:11 PM
^Yep, I knew that. My .44 mould is made for gas checks. Thanks for the reminder, though, someone else may need it.

I took a platic tipped hammer and tapped the gas checks into place before running them through the lubri-sizer. It seemed to work just fine.

January 14, 2010, 08:16 AM
I have the Lyman 450 Lube/Sizer, I bought the G/C seater for it But have only used it a few times. I use a Lyman mold. And try to get as close to Lyman #2 . In my Lead mix. Most G/C I snap on the bullet as square as possible on the Bench. And just run threw the Sizer. to lock on. If having trouble with the checks. It could be the Alloy. the as cast Diameter of the base.

January 21, 2010, 09:40 AM
^Dude, English.

January 21, 2010, 11:46 AM
^maybe his mind was going 300 MPH and his hands had a hard time keeping up with the typing... :D

January 22, 2010, 08:11 AM
To simplify. Lyman number 2 . Is the Lead to alloy mix Lyman has used for years .As a standard mix. That is recommended for their molds. As cast Is the term used . when using different Alloys to produce a harder or softer Bullet. The higher the Antimony percentage the larger the Bullet. An example. A 357 bullet cast out of pure lead will drop a .3578 Dia, = 215 grain bullet. but a Bullet cast from Lyno-type will cast a .3594 Dia,=200 Grain bullet from the same mold. And as you know. The sizing die has no effect on the base of a Gas checked Bullet. So The more Antimony the larger the base. And the harder the Gas checks are to snap on.

January 30, 2010, 04:51 PM
I am seating gas checks with my new RCBS Lube-a-Matic II (late 2009 production) and a new Lyman gas check seater. They do fit together, just not in the way I expected.

The gas check seater does not contact the gas check. Instead, it is used below the die, snapping around the threaded rod underneath. It locks the piston up, so that you don't get lube and have more leverage to seat the gas check.

You probably should have called RCBS product support, not Lyman.

Here's an image of it mounted and unmounted.

January 30, 2010, 05:04 PM
Welcome to the forum.

You are correct. It's a variation on setting the sized bullet ejector plunger up to bump bullets up to a slightly wider diameter. Gives you something to push against is all.