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.

With the GC positioned in such a manner it would separate from the projectile after exiting the muzzle. This is the same as a sabot, or shotgun wad. It'd be ok to try in a solid barrel with integral chamber. Due to concern for wheel gun mixup I wouldn't try this arrangement

There is also an unintended consequence of a copper GC flying in some unintentional direction..probably not recommended

Indoor range director might frown on the blown shooting lane lights

I see what you're talking about. I was thinking about the internal ballistics part of the event.

I notched the edge of an Oehler 33 skyscreen.

Ive done more than that to a perfectly good shooting chrony. It didn't work too well after the direct hit through the screen with a 280 Remington.

I've never made a direct hit, I was thinking of the wayward gas check in my experiment long ago.

Yes, did that with the 74 Sharps, 45-110. Worked, but didn`t see the need for the extra fooling around, as some would not seat flat on top of the powder. Try it.
Eventually had a 405grn. PP mold made, PPing solved some problems, created some others.

I think the best load I`d developed was a duplex, smokeless and Black, shooting a 405 grn PP "express" load. Safe in my rifle, and used it only for hunting.

I tried that in a .30-30 a long time ago. It worked as far as it goes, but the real issue, for me anyway, was getting the fool thing into the case neck.

Here's another dodge to get around GC usage: paper patching. Any of you BPCR guys employ that? I never did, but I did try the old fad of wrapping a .30 bullet with teflon plumber's tape. It worked pretty good - no leading, decently good accuracy and high-ish velocity with a soft bullet, but in the end was enough of a pain in the butt that I dropped it.

Uhm... YES! Except my powder was RL-7

Simply, but absolutely, untrue.

So Veral Smith is wrong and cores melt in jacketed bullets from hot gasses?

Educate us.

This is something that each individual needs to shoot and see for themselves. Everyone needs to avail themselves to the vast recorded history of those who's done this before and then proceed with caution. Everyone has a barrel that will be a law unto itself as to how well it handles cast lead bullets. They need to be. 001 to .002" over for a sure snug fit that will never allow the hot gases to sneak by. Barrels need to be completely free of any other type of fouling. Don't ever try shooting lead bullets in a barrel with copper fouling. Slightly undersized lead bullets leads to large amounts of lead fouling. We can debate the particulars on how or why this happens, but we know that it happens and how to avoid it. In my experience gas checks are often worth the time and trouble because they pay off in spades with accuracy and speed performance.

We have good banter here on this forum; if I don't agree or have a difference I will always try to explain why. I have a great deal of respect for everyone on this quieter forum. If I'm full of horse manure I can live with being wrong.

I agree, barrels can be a law unto themselves. I shoot jacketed stuff with cast all of the time from several rifles. I don't clean them much unless its humid because they really don't foul much.

If a barrel copper fouls or in fouls certain places, its going to foul with cast in those same areas, usually worse, even when clean. Copper fouling is there because of friction, pressure and finish, but lead fouls because of gases? Copper layering produces a rougher on an already rough finish, so yes I agree, its going to mess with a cast bullet which needs to have a seal for support and needs a smoother, more even finish.This is the contact area that makes the gas check help.

A loose core or one that is distorted beyond its strength within a jacket will become molten without contact from hot gases in the same way it does in a barrel. The snug fit is for support and balance and to minimize heat from moving under stress at its weakest contact area, just like it is in a core.

It is also always not true that they need to be .001 to .002 over or not slightly undersized to not lead or work. This is why many like softer alloys because the base can bump up and create that seal and base support. Elmer Keith touted "exact groove diameter" for sizing cast bullets, but he got around leading (we think) by using soft enough alloys and pressure within the limits of the alloy and lube. The old outside lubricated Colt rounds with straight chambers needed hollow based bullets and soft alloys or they were flat dismal, but they worked despite being undersized on purpose.

But agreed, starting off with a snug fit makes life much easier. But even when you have even an oversized bullet you will still see a recovered PB bullet with distortions at the very edge of the bullet base where stress is the greatest and on the leeward edges where rifling is engaged, despite having plugged everything up.

If lube runs out you will also see leading even with a gas checked bullet, often at a rifle muzzle, despite having sealed off all of the gases and the lube. The lube's ability to do its job doesn't expire from hot gases, its expired by friction.

Another explanation is high temp grease, wax paper fillers,dacron filler,card wads, fiber wads,plastic shot buffer filler for a bullet base.

Every one of these items will burn up on top of your lead pot way before your pot is close to being molten, yet every one generally exists when fired pretty much in the state they started in the case, despite being exposed to gases that that are hot enough to supposedly melt lead.

We use these items to move the stress area at that base edge, to cut down on the pressure and friction lead is exposed to on that base edge, just like a gas check. I still question the notion we use them to keep the base from melting due to gases.

Sorry fellas, I don't care about the SB today!

I couldn't agree more!

You've made me re-think a bit my feelings about gas cutting. I will agree in the main about friction etc. being the culprit, but must also think that gas cutting does have a somewhat deleterious effect on the stabilization of the bullet as it makes its way down the barrel.

At the end of the day, what all this analyzing, theorizing, and posturing points to is the base of the bullet is key to its successful flight. If the base isn't flat and square, and sufficiently large (either through bumping out or proper sizing) to seal the bore, it simply won't fly true - it is indeed the steering end of the bullet. Of course other things factor in too, but this speaks to the heart of the matter. At high(er) velocities the gas check serves in several capacities, but maintaining the integrity of the bullet's bases is chief among them.

As I mentioned before, Charlie Dell's experiments conducted by observing captured plain base bullets shows conclusively (to me anyway) that it isn't hot gases that wreck a soft PB bullet's base, rather not-yet-burned powder granules having a sandblasting effect. My own experimenting with PB soft cast bullets in my couple of .32-40 High Wall target guns (one of which is Pope #53), breech seating with over-groove diameter bullets so there's no question about starting with a perfectly sealed bore, show a marked increase in accuracy when I interpose a thick felt wad behind it (best) or a wax wad (even better). I think (but I could be wrong) that the wads simply protect the bullet bases from the sandblasting. (Bullets are lubed sufficiently as I enjoy a heavy lube star on the muzzles even without the wax wads, and the lube I use is a simple 75/25 mix of beeswax and Alox, not terribly high tech.) Besides, I need a wad in the case mouth to keep myself from spilling powder as I insert the thing into the chamber behind the pre-seated bullet!

Of course, the above is really only germane in discussing low velocity soft PB cast bullets at modest velocities. I have little personal knowledge of high velocity (over 2000fps) protocols. I have no desire for such - I simply have no need at this time although I might change my tune if my insanely big stash of jacketed bullets for .22CF's dries up - my academic cast bullet interests lie firmly in the 800-1800fps range, rifle and pistol.

A good read on gas checks.

http://www.lasc.us/Fryxell_Book_Chapter_10_GCkorPB.htm

Just a dumb old guy with sixty years of casting, loading and shooting. My experiences: under 750-800 fps, good lube, sized to throat dia, plain base fine with wheel weight metal.
1000 and up, I use gas check bullets and get no leading. Again, wheel weight metal
Rifle, mainly 308/30-06. Linotype, gas check, sized to bore dia, beeswax/alox, 2000 fps, no lead.
Leading galore with "hard cast" bullets and the damn crayon lubes.
Argue, debate, fuss all you want. I know what works for me. Ain't puttin painted bullets down my lapped barrels.

I have 2 1894 Marlins with micro groove barrels a 357 & a 44mag both like wheel wt metal and Hornady gas checks. That makes for inexpensive shooting.
.mb

Shooting lead it fun, and educational. I’ve driven pure lead plain base to 1600 fps with MOA precision. Card wads help, so to does paper patch. Fastest I’ve shot without patch was 1400 fps, so my chronograph says. No leading. 9 BHN gas checked from a .30-30 ~2100 fps. No leading.

Bullet fit is more important than the other trivia.

I'm reviving an old technique for shooting plain base rifle bullets. Wax wads. My first trial consists of A.O.Niedner's formula: 2 parts beeswax/2 parts Japan Wax/1 part colloidal graphite - as published in Phil Sharpe's handloading book, and measured out in ounces (2,2,&1). Initial mix didn't turn out too good, it was rather hard and flaky. I re-melted everything and added another 1/2oz. Japan Wax plus one teaspoon of castor oil. Bingo, it pours nicely onto wax paper and flows out to about a heavy 1/16" thick puddle. Cools/hardens quickly. Cut into 3"x3" squares and squirrel away with wax paper between them.

The plan is to use them in .32-40 breech seating. There's no risk of leading in the way I'm currently doing it (14 grains 4227, 1:20 alloy 185gr. bullet) but I'm always scouting for a little more of an edge in accuracy. Last season I hit upon using dental wax wads (available in sheet form, on eBay) in the mouths of these cartridges and I saw a distinct increase in accuracy out of my two .32-40 High Wall competition guns. But, I also discovered some fairly nasty hard wax buildup in the throat when I went to clean them. I didn't like the looks of that, despite the great accuracy. Hence the search for a friendlier wax wad - and I figured "why re-invent the wheel when guys like Niedner, Roberts, Sharpe, et al already did the legwork over 100 years ago?" (But actually their efforts were geared toward increased velocity with less or no leading.)

If it works as hoped I'll expand the experiment to other cast bullet applications. The old timers also used graphite-bearing wax wads behind jacketed bullets (for added velocity), but the reportage at the time had mixed reviews. We shall see about that also.

Protocol for use: simply press the sheet of wax over the mouth of the charged case, like a cookie cutter, leaving a thin wad of wax in the case mouth. Seat bullet, or in my instance shove the thing into the chamber behind a bullet pre-seated up into the rifling ahead of the chamber. I had been using wads punched out of 1/8" hard felt or card wads punched out of bar coasters - but they were more for keeping the powder from spilling out of the case on its journey into the chamber than an edge for accuracy or to combat leading.

Stay tuned boys and girls.

Well said.

I use GC’s in heavier loads.
There’s many different factors in getting good shooting cast loads. Some say it’s an art not a science, IDK. GC bullets almost always work for me as well as plain base. But I use plain base in many cartridges, mainly because the extra cost of the gas check isn’t worth it in mild loads.

Top group is the 311041 w/o the gas check. Why bother?

Bottom group is a plain base.

Regarding bullet fit:
I have a new to me Model 71 348. I ordered .001” over-size and .002” over size cast bullets and took them to the range, identical powder in new cases.
The group size was as close to exact same size as I could measure with calipers.
It’s my opinion that bullets that are undersized except for perhaps near pure lead is more of a problem that oversized.

There are many ways to screw up cast bullets: too hard, too soft, imperfect bullet shape, undersized, imperfect lube, pushing too fast - it’s not just one thing.

Need GC?
I load 30-30 cast to the same velocity as jacketed bullets. I suppose it’s possible to do that successfully without GC’s, I have not done so. But I imagine others have.