Home Forums Reloading Bullet Casting PB or GC?

Very new to cast bullets. Is the idea behind a GC that you can drive them faster than a PB cast bullet?

Good question. I can’t give a solid explanation. Don’t know. I’d guess that gas checks do what they are called, eliminate/reduce gas cutting. Personally I’ve not used many. Cast a few molds that are made for them but after discovering powder coating the checks just sit.

I’m by no means an authority on anything involving cast bullets. Like you, I look forward to others comments and experiences.

Yes it does keep gas from messing up the bases.

A gas check does several things: it strengthens the outer edge of the base of a lead bullet where pressure, friction and stripping on the lands make it susceptible to lead on the barrel contact and it keeps layered leading down as it scrapes the bore at full diameter. This is why they can be driven faster at higher ambient temps in a hot gun or rough gun, repeatedly.

"Gas" doesn't melt a lead bullet base as any fired, recovered bullet will show. There's no melting around the sprue or base or unchecked shank at all, ever, EXCEPT that outer edge where pressure and friction and land engagement with the barrel contact is made.

The base of a bullet is the area that has the greatest pressure applied to it and is the weakest point of a lead bullet; if there is too much pressure (heat), friction (heat) and it strips (heat), it can lead.

HawkI, thank you for the explanation. Appreciate it!

HawkI, great answer!

I cast gas check bullets for my full power .357 and .44 mag pistol loads, and for my .257, .30, and .375 caliber rifle loads.

I cast plain base bullets for all of my other pistol loads: 9mm, .38 and .44 spl, lower velocity .44 mag, and .45 acp.

In over 50 years of shooting thousands of these bullets, I've never had any problems of leading in the barrels.

When cores melt in a jacketed bullet, it isn't from gasses. Its the core slipping inside the jacket from rotational load and pressure on the barrel wall.

That's why thin jackets and non-concentric bullet cores go poof when twist gets too steep. Its also the reason fit with cast is so important.

If you don't have full diameter support and a seal or bad barrel conditions the lead moves/slips and under load with barrel friction it exceeds its melting point in those "loose" areas, causing leading. This is why some get leading even from hard alloys and prefer softer ones; there needs to be a seal. The load bearing ability of a harder alloy is going to be greater.

Gas checks help keep these minor areas of poor fit and leading cleaned up and consistent. It also prevents slippage at that most stressed area.

The coated bullets do similar things but most importantly it is lubrication between the bore and lead, especially at the base to bore contact area where pressure and friction from that pressure is greatest.

I really don't use any gas checked stuff in any handguns.

In most cases, you can forget the gas checks and just PC for pistol loads.

HawkI is correct. Gas cutting happens where the bullet contacts the barrel/grooves/lands and not at the base. Here is a recovered 440 grain Lee casting that I powder-coated and tested without a gas check. The base and all the way up the gas check shank have the PC still in tact but you can see gas-cutting after that. PC is tough but not Magnum tough.

Folks it isn't "gas cutting" and it isn't a "gas check", per se.

Lead bullets, and even jacketed bullets for that matter, have a contact point with the bore were friction is at its greatest; gas has nothing to do with it and its a function of pressure and friction.

Read again; gas isn't doing anything, its pressure and friction that causes leading......


Quit with the "gas cutting"; as you can see from the above bullet, the area with the most stress with pressure and friction is what's getting deformed and melting; other parts exposed to "hot gas" aren't doing anything.

In most cases you don't need PC.....

If you have everything aligned you don't lube or very little at close to the stress/pressure area.

They were called a "gas Check" long before you knew everything, so please...

I go from being "correct" to being denigrated as a know it all defying logic that's been around longer than I have. Whatever.

What I do know is that there aren't any favors to the OP or anyone else wanting to get started making their own bullets if 100 year old bullschidt gets propped up as any kind of wisdom or even a place to start.

Having been in the same shoes as the OP, anyone telling you "gas cutting" is causing all your leading and you need a "gas check" to keep hot gasses from turning your bore into a solder bar isn't a help to anyone.

You stated as much yourself and thanks for the illustration.

The GC vs. PB debate has been exercised in cast bullet circles for a loooong time. I'm not getting into this one. Frankly, for cast bullet handgun shooting I don't shoot magnum cartridges, never have to speak of and never will (I don't like being smacked around with each pull of the trigger) so I can't speak to that from personal experience now anyway. For me .32 Longs, .38 Spl, .45 ACP and Colt, and a few 9mm's now and then are it - and PB bullets satisfy me completely.

I can speak to their use in rifles though, ad nauseum. An inveterate innovator/experimenter with schuetzen rifles named Charlie Dell conducted lengthy experiments with .32-40 bullets a generation ago and came to the conclusion that the sand blasted bases of PB bullets (viewed on bullets he captured in snow banks) had a detrimental effect on accuracy, "sandblasting" caused by impact of unburned powder kernels before they were ignited*. Further testing on bullets that purposely didn't fit the bore showed distinct signs of "gas cutting"- streaks of melting along the rifling engraving on the bullets - and coincidentally the bores in which they were fired in were gobbed up with lead (when they never exhibited leading before). Subsequent construction of identical bullets but with GC's (from a mold made with the same cherry, but altered to create a GC shank) yielded better accuracy and zero leading with no signs of gas cutting in the rifling engraving. Conclusion: since the bullet base is the steering end of a rifle bullet, any time you screw with it in any way you're going to mess up accuracy (a moot point maybe when it comes to putting a magazine full of pistol rounds into a silhouette target at 10 yards). (And golly, Dr. Mann proved that conclusively 110 years ago - yet we insist on re-inventing the wheel every generation.)

It's no secret that GC rifle bullets sans GC's deliver excellent service at low velocity, but fall on their faces if velocity is stepped up and GC's are still absent - the various effects of powder spanking them. And oh my, try shooting a PB bullet (or a GC bullet without a GC) at 2000 fps some time - and get back to me. Powder coating may well (probably will) ameliorate that, but someone else is gonna have to tell me about it.

*His assistant in those experiments is still with us and described in detail the course of those tests to me over beers and a campfire a couple years ago after a match. Those results parallel pretty closely my own experiences/observations, with target rifles and cast bullets, not, like I said with pistol bullets though. (It's why I insert a wax wad in the .32-40 case mouth before inserting it into the chamber behind a previously breech seated bullet.) With pistols as long as I can hit our little steel targets on my buddy's plinking range and I don't have to scrub lead out of the barrel later, I'm good to go (and strict attention to bullet fit and alloy creation takes care of that, the actual target hitting or not hitting is on me). But, I can't help but believe a lot of the lessons from rifle shooting apply to pistols too - I just don't care enough to find out comprehensibly because of my aforementioned pistol needs.

For me plain bases are fine in pistols to about 900 fps, and I have run a beveled base pistol 158 swc in a Whelen to 1450 fps with 13.0grs bluedot to great accuracy and no leading problems. I won't be pushing these speeds with the plain base loads. Gas checks change everything, and if you're really up for a chore apply them to low velocity loads. Petersons Publications Handloader cast bullet expert Mike Venturino came to the conclusion that gas checked bullets are usually/almost always more accurate and plain bases at any speeds.

For my own hunting loads GC rifle bullets can be pushed to 2500 fps with about the same accuracy as military ball surplus. 1 MOA is easily produced in an accurate target rifle and about 2 MOA with irons at 100 yds. I make my own beeswax based lube and haven't seen a need to switch to a PC operation

I wish we all lived close enough so we could gather around a wood stove and gab about this stuff!

I'll still trade you IMR SR-4759 for IMR-4198

Has anybody ever seated a plain base bullet on top of a reversed gas check on top of a compressed load of powder?

That would be basically like a sabot. could have alignment issues in a revolver barrel with cylinder gap. I wouldn't try it

I don't understand how it would be like a sabot. The cupped side is facing the powder.

I could see the back end of the check trying to flare into a barrel-cylinder gap, but there isn't one in a Contender barrel for one example.