Howdy all, I need you expert help again. I’m looking at bullets and ran across this. “This bullet is gas checked and will not lead your barrel.” Can someone tell me what a gas checked bullet is? And if it’s lead how does it not lead the barrel?
Thanks Paul

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Proud Life NRA and TSRA member

Gas checks are copper "cups" that are installed over the base of the bullet during the lube/sizing process. This prevents the hot gases generated by the exploding powder from melting the base of the bullet and contributing to leading. It also has a "sweeping" effect to clean any leading left in the rifling by the driving band or body of the bullet ahead of the gas-check.

Adios,

Pizza Bob

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NRA Benefactor Member

Thanks that helps.

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Proud Life NRA and TSRA member

Gas checked bullets have been around for a loooooooooong time. There are hot factory rounds that are or have been gas checked such the 357 as well 41 & 44 mag rounds.
Presuming the cup is properly crimped to the base of the bullet - you safe to go.

To clarify, all lead bullets (gas checked or not) will leave some lead residue.

The goal is to leave very little and for it to be self limiting. Gas checks are one way to get that done. But not the only one.

Selecting bullets cast with a lead alloy of a hardness such that the base of the bullet obturates (expands and seals) correctly against the bore is another way.

The harder the lead is not always the right answer. For non magnum velocities, too hard an alloy (Brinell 18 or more) will leave too much deposited lead as the gas pressures generated by non magnum loads are usually insufficient to obturate bullets that hard. Incomplete obturation leads to gas blow by around the sides of the bullet, resulting in tons of molten lead stripped off the bullet and onto your barrel grooves. Brinell 12 is a better hardness choice for velocities 1000 fps and under.

Not to hijack this thread, but the original question has been answered. I'm curious to know how many old-timers (and I count myself among you) remember zinc washers for cast bullets that were to be driven at magnum velocities. I've never seen one in place, but in the early 70's I came across a box of the washers while poking around at my favorite home-based FFL. Apparently they were cast in place. Anybody shed anymore light on this?

Adios,

Pizza Bob

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NRA Benefactor Member

Long ago, when I started casting for my .357 mag., I was looking for something to stop/slow leading on hi-vel loads. I was given some zinc washers and it was suggested I use them in lieu of gas checks.

The washers were not steel coated with zinc (as verified by a magnet) and one could bend and break them with pliers. I have no idea of the actual mixture....the guy who gave them to me couldn't tell me what the original purpose was.

Anyway, they fit nicely (with some care) in the bottom of my regular (not GC) mold, and I produced a couple of hundred or so. Shot them with no adverse effects, but I seemed to get better accuracy with a similar mold designed for GC bullets.

Incidentally, those zinc washers were available from NEI (which was then close to me), but more costly than gas checks. As I recall, it was a lot more hassle getting the washers in place; GC were easily put on during the size/lube process.

Here's a 265g 44 with gas check.



Pre gas check and lubrication, the same bullet(s).



Group photo, ready for loading.

Very nice home brews.
I don't have the room or patience to cast my own but I do love shootin' 'em.
Some 44 LBT WFNGC's:

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Nemo

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Thanks Guys, I really appreciate all your help!

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Proud Life NRA and TSRA member

I have a Taylor's Arms 45-70 Sharp's clone -- Quigley -- that I shoot gas checked 420 bullets in without any leading in the 32" barrel. I has all the muzzle velocity I need in an 11# rifle. I have never had any leading, but do use factory cast rifle bullet lube, currently using Lyman Orange Lube.

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S&WHF 366

This isn't exactly on topic but it is pertinent. Expound on the cost of gas checked bullets? Depending on whether you make your own (cheap and no extra operation to go through) or if you buy gas checked bullets. The cost of what I've looked at appears to be less than jacketed, but more than plain base. When I looked at these before it seemed the price was close enough to the jacketed for me just to make the leap and go jacketed. I've just got into lead bullets this last years and I seem to have bullets that work for my rifles, pistols and revolvers. If I find that I'm getting lead, a gas check might be the next to look in to.

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"He was kinda funny lookin'"

The zinc washers were for the Prot-X-Bore bullets, originally swaged, that were offered in the early '50s by Jim Harvey of Lakeville Arms (CT). He is better known on this forum for the Harvey .224 Kay-Chuk K-22 conversions and his Shot revolver conversions.

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Good shooting.

Rather than paying for gas checked bullets, I would look at polymer coated bullets.

They achieve the same end but should be cheaper since the polymer coating process is done in batches instead of one piece at a time.

I'll admit I have not really looked into the coated bullets except for what I read here.
Have they really been proven to stand up to full magnum pressure and velocity?
That's one of the big advantages of the gas check.

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Nemo

A couple of my own thoughts regarding gas checked bullets:

1) Gas checks in handguns are an answer to a non-existent problem IF the following variables are properly controlled: a) bullet alloy; b) bullet sizing; and c) proper lubricant, not necessarily in any special order. As has already been stated, too hard a bullet is going to lead as it does not upset and fill the bore entirely. Ditto for the wrong size bullet, and that can be a factor of nothing any more exotic than cylinder throat size versus barrel groove diameter. Finally, the wrong lube is just as bad as no lube at all.

2) No less an authority on cast bullets than Wayne Gibbs once told me directly during a phone conversation that "if a bullet is sized properly, has the right lube on it and is of the proper hardness, there is no reason for it to be gas checked for handgun use if velocities are kept to below 2000 fps." When I asked him why Hensley and Gibbs offered gas checked handgun moulds, he told me "Because the customer is always right."

I cast for other folks on occasion, and if they want gas checked bullets that is what they get. I don't gas check any of my own hard cast handgun projectiles. I have worked to determine the proper alloy, have found the right lube for my applications, and have found through trial and error that nominally speaking, .001" over groove diameter works with what I shoot.

Besides: gas checks add about $2.00 to the cost of a box of 50 cartridges, and that adds up over time...

FWIW, the above is good information.

I have both Ray Thompson/Lyman moulds - 44 and 357.

If you size the bullets .001 over bore size, ie. .358 in a .357, you allow the bullet to seal and obdurate in the bore which keeps the hot gas from going down the sides of the bullet and melting it and THAT is the source of leading.

I consistently do not use the gas checks for non magnum loads, cheap so and so that I am.

I use them for hot 44's and 357's because that's the design of the mould and I like to do things according to the original intent, but I have other non gas checked designs for all my calibers and I push them full power without leading.

Lube and alloy are also important, but size is #1 on the runway.

I guess I should have mentioned that with the exception of the CP 260 WFNGC,
(which is one the most accurate bullets I ever shot out of a handgun),
the other, heavier, numbers are primarily for use in the 445 and 444.
Both of these can go 10k PSI MORE than a magnum revolver cartridge.
That's the main reason I started playing with gas checks.
Cleaning lead out a micro-groove rifle is less fun than a revolver
This is one case where a hard bullet makes sense.
I am still learning the fine points about all this and probably always will as I tend to be a slow learner.

I agree totally with all the above wisdom about bullet fit.
I have cast 44s from .429 to .432 as a result.
The .429s are usually too small for anything.

This is about as good as I am ever going to shoot with iron sights and bifocals at the age of 65:

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Nemo

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Hey Snapping Twig - aren't you in violation of some kind of San Francisco ordinance?

I can see the headline now - "Man found with arsenal of dangerous home made bullets".

Lot of 'if's in post #16.....

What if: (A) one has a large amount of mystery metal (mostly old fishing weights and wheel-weights) that casts lovely bullets, but leads barrels when fired at 1100+ fps? It's not a "non-existent problem."

What if: one came upon a gas-check mold (s) that solves (A). Said gas-check bullets work not only in all 18 revolvers one shoots, but also in 5 different rifles?

Well, we're down to only one "what-if," right? Don't have to keep 23+ different sized bullets for hi-vel loads.

And, honestly, I have yet to fire a non-GC bullet at 1900 fps in my .357 rifle that doesn't lead....and I don't care how carefully one fits it to the bore......

Shhhhhh!

They'll hear you....

Honestly, something's wrong.

I make 'em from fishing weights, wheel weights and linotype and all combinations therein.

Get some Red Label BAC lube, it's important what you lube with as well as size being .001 over bore.

I made my friend 100 .357's for his 1894. Loaded 'em up... uh ... in excess of common sense. Perhaps like the Ruger and TC only data you'd find in the back of the manual.

Zero leading. I loaded 50 gas checked 160g Thompson's and 50 of the 170g Keiths.

If the BHN is too low leading can also occur.

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No good deed goes unpunished.

The HI TEK coating works great. Excellent product, but I still use a variety of lubes when not running coated projectiles.

There was a special mold for them. The washer was put in place. There was a hole in it and the mold had a small area under the washer to lock it in place. I had a 45 cal mold that was given to me at one time. Couldnt find the washers so never tried it. There were no lube grooves on the about 200 gr SWC the mold was made for. Dont know how well it worked.

Nothing wrong with a gas checked bullet. Does cost a bit more to make. If you dont cast your own bullets then it is hard to get just the right combination of alloy and sizing. The gas check can make up for this. Always had good luck with the store bought gas check bullets, especially for high velocity loads. You will have to try them yourself. Some guns will lead no matter what you do and gas checks have been the cure for me.

To remove leading easily, wrap some material from a Chore Boy all copper scouring pad around a cleaning brush for a tight fit in the bore.

Concerning the lead VS jacketed bullets, the lead bullets put less wear on the bore. Especially for older guns.

For the higher velocity loads, I find that IMR4227 gives less leading with plain based bullets in revolvers.

More on the Prot-X-Bore:
The Prescription for your bore!
I read somewhere that one of the main downfalls of this system, aside from the hassle and weirdness,
was the tendency for the washers to depart the bullet at the muzzle leading both astray.
Might have been here; One of the best free online casting tomes I know of:
From Ingot to Target: A Cast Bullet Guide For Handgunners
A PDF is available in the upper left hand corner. Chapter 10 addresses the whole gas check idea.
There are many more Fryxell articles at the lasc.us site. Well written and informative.

At http://www.corbins.com/bgk-1.htm#top they state:
"It turned out that the washers could not be cut precisely enough to seal the bore, and that one edge was always rounded while the other was sharp. If the bullet maker put the rounded edge toward the bullet, there was no scraping or burnishing action to clear the bore. Also, if the washer was even a few ten thousandths smaller than the bullet, gas would leak around it and melt the lead into the bore."

I still find the chemical and metallurgical reasoning behind the zinc washer to be fascinating.
Using 2 unalloyable metals to lubricate one another is not a dumb concept IMHO.
It may also be that the change in bore dimension affected pressure and dynamics:
"Zinc will only sherardize to steel with a maximum build up of a 1-3 mil coating".
.003" in your bore is a LOT.

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Nemo

All great info above.

Many guns are designed to run jacketed and have issues with lead, such as S&W M&P Shields having a ledge which will shave bullets. The correct fix is to taper the ledge, but gas checks can be used with great results for a quick fix.

Sometimes gas checks can be used to increase accuracy.

You can also now buy and install gas checks on Plain base lead bullets with same results as using gas check molds. Many makers out there using aluminum soda cans, etc. with excellent results for years. Google Plain Base Gas Checks. Less than a penny a piece. This also opens up your choices of molds to use, as not limited to molds with gas check.

One example, no personal experience or recommendation

Photo below of ledge in 40 shield that will shave lead. See castboolits website for more discussion of this common issue. I used throating reamer to correct, but still use PB Gas Checks for better accuracy and less cleaning.

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40groove.jpg (42.3 KB, 10 views)