Gas Check Fit on Oversized Base

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  • Last Post 12 May 2026
Wm Cook posted this 07 May 2026

Has anyone ever had the need to expand the mouth of their gas checks before they were large enough to fit over the bullet base?

My practice is to add checks and size with the Lee in the nose up position, then lube in a Lyman 450 with a .001 oversized die.

Both Hornady & Gator’s checks were tried. I suppose it would be possible to custom grind a cheap punch to flair them a little. I have a Pat Marlin gas check maker on the shelf and that would eliminate the lip that crimps the check to the base. But I’m hesitant to take on another exciting new learning experience unless I absolutely have to. Any thoughts would be appreciated. Thanks Bill C.

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Tom Acheson posted this 07 May 2026

I don’t suppose the gizmo that NOE offered would help. It removed the burr on the edge of the gas check shank and applied a small chamfer to edge of the shank, allowing the check to get started more easily.

Tom

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Waleone posted this 07 May 2026

A properly sized ball bearing with a light hammer tap works to flare the gas check, but with my fingers desensitized from 50 years of picking up hot welding rod stubs and the like, was slow and frustrating. The NOE gas check expander works well. What also works is making a tapered punch to flare the gas checks. If the gas checks are set up on a piece of flat steel, this method is probably the fastest, and with practice is as precise as the NOE tool.

Wayne

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pat i posted this 07 May 2026

I have one of those NOE check expanders for a mold I got from him with an oversized shank and while it does work its a time consuming PIA. If it was me I'd just get or use a different mold and use the one you have as a plain base bullet.

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Wm Cook posted this 07 May 2026

Sometimes the “like to have” and what is realistic available can’t be found in the same sentence. I’d like to keep the gas check as this is for competition and velocities that it’ll be shot at is unknown.

And unless someone has a NOE flaring punch/base for a .22 that’d be a dead end.

As of now the options look to be a ground punch or a ball bearing ( .250?) held with a narrow nose 6” vise grips and a flat piece of steel. Bill C.

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Millelacs posted this 07 May 2026

Waaaaayyyyyy back, there was an article in the Fouling Shot where a guy used a machine screw to expand the gas check. If I remember correctly, he used a No 10 round head screw for .30 cal gas checks.

If that doesn’t work try a different size machine screw or different style head.

You can also play with different size screws and head styles for different caliber gas checks.

I modified a couple of hole punches so I didn’t have to hold the screw shank with my fingers, when I whacked the screw with a hammer.

I used up that batch of gas checks and haven’t needed the expanders for a long time.

I’m out of town at the moment, but after I get home next week I’ll see about dragging them out so I can post a couple of pictires.

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Wm Cook posted this 07 May 2026

Millelacs, that screw head idea is a quick low impact way to take a step into expanding gas checks. Thanks for that. Bill.

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Mal in au posted this 07 May 2026

For my .30 cal lino pills a couple of moulds are a bit os ,I use a pencil sharpener ,turn it in reverse puts a nice bevel on ,helps to seat gc square . I also use 30 cal gc on my .303 projectiles using the sharpener,a bit slow but we get there. Mal in au.

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steveu posted this 08 May 2026

I have been using a Lee fcd to swage down the base enough to get the check on. Works well with the old Ideal moulds I have.

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OU812 posted this 08 May 2026

You can buy 3 foot steel rod in the size you need at HomeDepot. Cut you a short piece about 4 inches. Spin in drill press to taper the end using file, polish taper with fine grit sandpaper. Dial calipers help determine size needed. You can install a wood handle on end much like screw driver to flair gascheck by hand against hardwood.

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lotech posted this 08 May 2026

I have a very simple tool that with a quick twist of the wrist puts a slight bevel on the base of a cast bullet before attaching the gas check. This makes the gas check attachment by hand much easier before crimping. I haven't used it in some time and only have  a couple of bullet designs that require its use. I think it's a Don Eagan tool but don't recall if it's marked as such.   

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Paul Pollard posted this 08 May 2026

William,

In a conversation with Dave Lee at a National Match several years ago, I asked how he processed his bullets, since his accuracy was outstanding.

He said that he put his bullets in a tumbler, added a small amount of moly powder and threw in some gas checks. He said the gas checks would attach during tumbling.  I didn't believe it, but he assured me that it worked. On my return home, I tried it and it did work. I'll try to attach a photo of 6mm bullets and gas checks. Of 66 bullets, the gas checks attached to 51 of them in 15 minutes. Try it. It might save you some aggravation.bullets and gas checks

 

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Hornet posted this 09 May 2026

A little dry tumbling also reduced venting 'nubs' and sprue plate/parting line flash. I usually put mine in a heavy-duty Ziplock bag first and bury it in the media so I don't have to dig bits of walnut hull out of the grease grooves. DO NOT forget they're tumbling and wander off to work on something else for an hour. Lots of grey dust coating everything...

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OU812 posted this 09 May 2026

Do not flair gascheck too much. Flair just enough for a slip fit onto shank.

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9.3X62AL posted this 10 May 2026

My principal problem in this vein has been Lyman 30 and 35 caliber bullets and Hornady gas checks.  The NOE tools work well, and I don't use a whole lot of gas checks any more.  The issue has receded in response to my usage patterns.  

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Qc Pistolero posted this 10 May 2026

I took the rod from a door hinge and turned down the head to the appropriate dimension for my 38-55 GC.Done that spinning in a press drill.works A1

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Wm Cook posted this 10 May 2026

“ Done that spinning in a press drill.works A1”

Good idea.  Bill C

 

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OU812 posted this 11 May 2026

Elementary

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405 Grain posted this 11 May 2026

There's another way.  On some molds the gas check shank would cast oversize, while on other bullets powder coating would make the gas check shank too fat.  Instead of altering the checks to fit a defective shank, I've been making the shank the right size.  While fiddling around with this process I found that it could also be used to correct bore riding noses that either cast too fat, or become too fat after PC.  Here's a link:  https://castboolits.gunloads.com/showthread.php?485164-So-what-to-do-when-the-Gas-Check-s-too-Small

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Ken Campbell Iowa posted this 12 May 2026

for those thinking about collet squeezing gas checks, bullet bases, noses, and even a handy way to crimp or size case necks and many other uses ...

consider a cheap chinesium 5c collet closer ... there are a billion 5c collets out there in standard and blank sizes to modify ... ...   normal up to just over 1.0 inch ...cheap on ebay.  hardinge and royal are premium brands but cheap ones are fine for our hobby purposes.

choose a closer that is heavy enough to stabilize without having to fasten it to your bench.  also choose one that has a handy handle to actuate ..  search ebay for 5c collet closer and i probably have a few extra also if interested.   

some cheaper than lee dies !! ...

ken the closer

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