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Cast Bullets For Beginner And Expert - Joe Brennan
Chapter 4.2 - Gas Checks

A collection of comments on gas checks by various cast bullet shooters

     Gas checks are small shallow copper cups that go on the bases of bullets specifically designed for them. Some bullets are designed for gas checks, some (plain base bullets) aren’t.

     The purpose of the gas check is to allow use of cast bullets at higher velocities without leading. Plain base bullets can be used up to about 1400 fps with good accuracy and no leading. Gas checked bullets allow higher velocities without leading. Gas checks may be seated in the lubri-sizer, as part of the lubricating and sizing of the bullet

     Gas checks come in Lyman and Hornady brands, by caliber. (In the 2003 LBT catalog, Veral Smith, founder of Lead Bullet Technology, says that Lyman gas checks are made by and are the same as Hornaday.) There are 22 caliber and 24 caliber and so on up to 45 caliber gas checks. Lyman gas checks are designed to be a slip fit on the shank of the bullet, and it is said that they will come off the bullet after it leaves the gun. Hornady gas checks are designed to crimp on the shank of the bullet, and they do not come off the bullet if properly seated.

     I use Hornady gas checks exclusively, only because they are cheaper than Lyman. When I do not use a lubri-sizer I press the gas checks on by hand. I don’t know if the gas checks come off or not-I’ve recently fired one thousand 6.5 MM bullets gas checked by hand, from the same bench at the range, and have not found a single gas check on the ground.

     Some cast bullet shooters anneal gas checks.  The theory is that Hornady gas checks are hard, spring back after installation, and fall off the bullet after firing. Annealing gas checks makes them stay on bullet bases because they are softer and don’t spring back. Gas checks can be annealed by putting them on an electric range calrod unit, turning it on until it is red-hot, then turning it off and allowing everything to cool down. There are other methods involving pipe nipples and end caps and a heat source.

     I have a mold that makes 22 bullets with the gas check shank a little big, so that the gas checks go on hard if at all.

     Several folks recommended annealing the gas checks, I did, and they still went on hard.

     I fix the problem by tapping a round-head screw head into the gas checks, opening them up. Now they go on fine.

     Others segregate gas checks by weight. Perhaps some accuracy increase can be achieved by annealing or weight segregating.

     Gas check bullets can be fired without gas checks at lower velocities with good accuracy. I use the Lyman 311299 and 31141 without gas checks in my Martini single shot bench gun with good results.

     Sometimes we have to disassemble cartridges with gas checked bullets, and sometimes the gas check stays in the case. Flattening the case neck/mouth a little will allow the gas check to fall out, and save the case.

     I seat gas checks in my Lyman 450 Lubrisizer by turning the bottom adjustment screw way up so that the bullet with gas check started on the shank only goes into the die far enough so that the gas check is seated square. When I remember I turn the bullet ninety degrees and mash down with the handle again. This seating eliminates the problem of gas checks being cocked or not pushed onto the bullet base properly.

     "Seating and Crimping Gas Checks Without Lubing.

     Using the Lyman #450 Lubrisizer, I had a desire to seat and crimp-on gas checks and then use tumble lube with a variety of 30 caliber bullets.

     Because the bullets in question were heat treated/water quenched I did not want the .311 die body to touch the sides of the bullets because that would remove or destroy the alloy hardness by working the metal.

     For the Lyman "H&I" die set, the "H" die is the sizing chamber and the "I" die is the ejection rod. After fiddling around with the rig a few minutes I finally removed the nut that locks the adjustment for the "I" die stop and then was able to raise the die stop much higher. Leaving the lock nut hanging on a convenient nearby nail it was then really easy to run a bullet into the H die just barely far enough for the die to fully seat and crimp the Hornady gas check in place perfectly.

     I measured the depth to which the bullet was being inserted into the H die, and it was right at .350 inches. At that setting, the gas checks are properly installed but the driving bands of the alloy bullet are not significantly touched by the die. Sometimes the band nearest the gas check would show the slightest shiny area on the rearward edge of the band, but the amount of surface working of the alloy was minimal to zero.

     Once set up, it only needed changing the top punch to change from 311291 to 311332 to 311284 and so forth. I suppose it would simplify things if I were to install that lock nut on the top side of the frame extension instead of on the bottom side where the factory placed it. Next time I tear the rig apart I might do that."

John Bischoff

     "I tried some annealed GCs, and I can tell you if you're bumping bullets, you probably don't want to anneal the checks - they come out pretty sharp and square. Too much so I thought. Don't recall an accuracy difference."

Glenn Latham

     "Unlike Glenn, the whole reason I have found to use the annealed GC is to help when bumping bullets. It does leave a nice square base with fairly sharp corners which I haven't found to be a problem but they do reverse in the bump die a lot easier than non-annealed GCs. When bumping bullets more than just a light taper, the hard GC doesn't want to let go of the bump die to eject the bullet. I have found that the annealed GC cures this problem. When just tapering the bullet, I find that I don't need the annealed GCs."

Dan Hudson

     "I too annealed gas checks at one time. I quit when I couldn’t get them annealed the way I wanted. I was finding that with closely fitted necks, some gas checks would spring back more than others and they would be tight in the chamber. I suspect that when most guys anneal them, they use such a high temp that they take them back to “dead soft”. For my purposes, this solved my spring-back problem but they were so weak (soft) that when bumping them, the check would extrude down around the base punch and I ‘d get slight fins on the bases. This did hurt accuracy as the best way I found was to just hit the bullet hard enough to flatten the base of the check but not lose the round edge.  

     Some shooters want the check lip to spring back so that there is a little flare on the forward edge. They think that this helps to scrape fouling from the barrel and keep it cleaner. I’m not convinced that this is even necessary. Lots of theories abound but I never recovered a bullet that showed any evidence of scraping."  

Tom Gray on CBA

     "My use of annealed checks was prompted by the .45-70. A number of the
moulds drop bullets with GC shanks ever so slightly too small such that when sized in a .459 die, I could pull the check back off with relative ease.

     Once the checks were annealed to dead soft - they would grip the shank
beautifully with a good snug fit."

Skyler Child

     "You might try annealing, stress relieving, them with a grain alcohol flame, just long enough to get them hot, not red hot, but enough to lessen the “spring” or hardness it them. I would experiment with one at a time, hold them for timed amounts, 5, 10, 15, 20 seconds or so until they seated without undue effort. I use this method to anneal my case necks one at a time, holding the cases until I feel the heat, then air cool the cases. Then, perhaps a batch of gas checks held in a wire harness could be heated in a much larger alcohol flame.

     I think this method actually reduces the stresses induced in the case necks from sizing and does not adversely affect the necessary hardness needed in the necks."

Bill McGraw

Gas Checks On Pistol Bullets

     I know nothing about auto-load pistols, and very little about shooting cast bullets in revolvers.

     Elmer Keith said that good accuracy at high velocities without leading was achievable in revolvers with plain based bullets of the proper alloy and size.

     Other shooters and writers maintain (ed) that gas checks are necessary to eliminate leading at high velocities in revolvers.

     In the 1958 Lyman "Handbook Of Cast Bullets", page 88 has Elmer's recommendations of plain based bullets  for revolvers. He ends with:" Properly cast, sized and lubricated they give no leading in any caliber."

     The facing page, 89, has Ray Thompson's recommendations for gas checked bullets in revolvers and the 45 auto-load pistol. He begins with:" I designed these bullets with gas checks primarily for the elimination of leading in Magnum loads, with excellent accuracy both at long range and target."

The debate continues.

     "There are a thousand and one reasons to use GCs on a pistol bullet. Just the same number as not to.

GCs solve problems.

     If you shoot at a firing rate fast enough that you out run the capability of your lube is a good reason.

     Another is if I need a faster powder to get good ignition. Usually lighter bullets benefit from a GC.

     A GC enables me to shoot a cheaper / softer mix of lead or at higher velocities.

     You will run into some revolvers that are mechanically out of sync enough that you can never shoot plain base with it without leading. Even if you fire lap.

     Or you like to use the same bullet in handgun and rifle combo where one or the other or both don't handle the pressure and lead.

     Or you are shooting a bullet so large in diameter (.434 and up) and you don't want to over do belling your brass, thus shortening case life.

     Just a few of the reasons I do from time to time."

John Robinson

     "GCs in a peestol be a unnecessary, added expense PITA most of the time.

     I use them when I have a special purpose load where I have to use a smaller diameter bullet than I'd like to in a pistol.

     The .30 Carbine Ruger comes to mind. I'm forced to use .309" bullets when I'd like to use .311. Some brass won't let me use bullets that big. I know, stuff them in and use a taper crimper. Problem is when you pull and measure, they're down to .309 anyway. In this case, a .309 with a GC at higher velocities is the answer and eliminates the leading I'd get with a PB design sized to .309.

     The other case is the Lyman 358156/HP in the .357 Mag. It's made for one and normally, I'll get leading unless I use one. I have dehorned a 358156HP and it works good even at .357 Mag velocities.

     IMHO, there's no use for a GC in a pistol if you have a plain base bullet that's big enough and I've dehorned (milled out the gas check shank on the mold, making it a plain-based mold)  maybe a dozen different revolver bullets from .32 through .45 Colt."

John Goins (beagle)

     "Overall, plain base boolits in revolvers do all right until about 1200 FPS for me before accuracy degrades markedly. Gas checks allow higher velocities with accuracy in most cases--although I use a LOT more in 30/32 and 38/357 calibers than in the larger bores. I just don't enjoy recoil as much as I used to, I guess."

Deputy Al on Cast Boolits

     "After catching all kinds of boolits for 50 years, I have never seen a melted base. In fact when Dacron is used as a filler, IT DOES NOT MELT. I pick up tufts on the range all the time. Even a plastic or fiber wad at the base of a boolit does not melt or burn. I use newspaper wads down over the flash hole in some loads and they just blacken and still can be recognized as paper. Gas cutting on the sides from a poor fitting boolit, YES, but no melted bases. The gas check really only works to scrape some of the leading from the bore. The proper fit boolit, alloy and lube will stop leading anyway so the gas check would not be needed until velocity gets so high that the boolit can be distorted from the PRESSURE, not heat. The boolit is in the bore so short of a time that it does not get hot enough to melt. The gas exceeds the melting point of steel but does not melt the bore either unless you shoot as fast as a machine gun so the heat can't dissipate. Even then, you will not see melted bullets exit the bore."

44 Man Cast Boolits

     "I own a Freedom Arms .454 Casull, and it will not accept a boolit sized anymore than .4515", the chamber throats are too tight. The bore is .452", and any plain based boolit fired at full pressure is guaranteed to lead. I have done the heat treating and water quenching, for me it's easier and faster to use a gas check."

454PB Cast Boolits

     "I use gas checks in my 44 Mags on my 300 gr FNGC from MM. I also use them in a Ruger Blackhawk in 30 Carbine. I like them in these 2 calibers and my mind won't be changed. I think the gas check gives a more perfect base on the bullet which aids in accuracy. I also shoot lots of PB bullets in 44 cal, 40 S&W and 357 cal. The PB bullets are definitely cheaper to shoot and a lot less work. Accuracy at the levels I shoot them are quite acceptable. Just sometimes I feel a gas check is called for."


     "If the bullet is made for a gas check, use it. I have never used one where it hurt accuracy, properly applied. Most of us are thrifty and don't want to "waste" an expensive piece of copper, so experiment with ways to do without the little buggers. Again, I have never used them and had them hurt accuracy."

Ric Bowman

Hornaday Gas Check Specs.

Shooting the Inverted Gas Check.

Forrest Asmus

     This past shooting season has been an enjoyable one for me. Our site monitor has encouraged me to write about the upside-down gas check idea which I have tried in my buffalo rifle with interesting and encouraging results.

     My rifle of choice this summer has been a Falling Block Works "J" action barreled up in 44/63 Ballard. I like this designation better than the better known 444 Marlin since I shoot mainly in the "traditional" matches but it is in fact the 444 chambered on a 16 twist barrel.

     In the process of load development I settled on a custom made, lathe bored 460 grain Mos bullet, 19 grains SR 4759, ¼ sheet T/P as filler and an un-sized, inverted, Hornady gas check as "standard".

     The inverted gas check idea came from CBA member and my correspondent Mustafa Curtess. In one letter Mustafa told me how he had been trying the inverted gas checks (IGC) in his 45/70 with good results. I loaded some up in the 44/63 and tried them out too. My results were very good and I continued to shoot this combination right along even though Mustafa later indicated that his results had not proven consistent and he was putting the idea on hold. I wondered what had gone wrong with his procedures and kept on using them in my shooting. I was having excellent results with the upside-down cups.

     Since this is a rather unusual utilization of a gas check I'll explain how I put them to use: The 44/63 case, being a straight sided design, allows me to seat the unsized IGC under the bullet without running the risk of a check dropping off, as might be possible in a bottle necked case. I start each check into the case about 0.060" by using a backed-off case expander punch. The IGC is then forced down as the bullet is seated on top of it, slightly compressing the column of T/P and powder. The procedure also prevents the check from moving away from the base of the bullet during handling and transport. This tight stacking of components is very important in my view because if the check were to move away from the bullet base it would then become a projectile inside the case upon firing. When it hit the base of a stationary bullet pressures would instantaneously rise, exceed the strength of the barrel steel and ring the chamber. I caution any member who contemplates trying this loading method to use the utmost caution!

     From my point of view the IGC serves three purposes: It does seal the hot powder gases just as well as a normally seated check and certainly better than a card wad does. During firing the check also scrapes the bore, removing any lead wash which might otherwise accumulate during the firing of plain base bullets. Then, I believe that the unsized check, being forced into the case ahead of the soft lead bullet, acts like an expander punch, opening the case just a bit more and reducing the amount of bullet deformation I have seen on bullet bodies which were forced into undersize cases. (My cases are only partially sized, but excess case neck tension is something we all know should be controlled to a bare minimum.)

     I have used this load for shooting matches and for everyday sessions at our range here in Wyoming. Excellent, consistent results have been my experience. In loading the IGC in my 45/70 I have found that any of the loads where I formerly used a 0.050 card wad under the bullet accept the use of a IGC without changing the load’s former dependability at all and accuracy is improved as noted above. The advantages of not having to be concerned about lead fouling are considerable, both because it no longer happens, and because worry itself is eliminated. In all cases, accuracy is improved.

Warning: All technical data mentioned, especially handloading and bullet casting, reflect the limited experience of individuals using specific tools, products, equipment and components under specific conditions and circumstances not necessarily reported in the article or on this web site and over which The Los Angeles Silhouette Club (LASC), this web site or the author has no control. The above has no control over the condition of your firearms or your methods, components, tools, techniques or circumstances and disclaims all and any responsibility for any person using any data mentioned.

Always consult recognized reloading manuals.


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