Gas check engagement on boolit shank

Hi guys and gals,
I have what might seem like a dumb question. I am installing .30 caliber gas checks from Sage's Outdoors on to Lee TL312-160 boolits, using a Lee .314" boolit sizer. I am finding that if I don't tap the boolit down into the check with a hammer before crimping it on using the sizer, the check doesn't engage as much of the boolit shank. It comes out square and I have fairly consistent boolit length, and they are on there securely, but I am concerned that there is a slight air space between the boolit and the check. Is this something that I should be worried about enough to take some sort of corrective action, or should I just not worry about it?

Scotty

What's the GC shank diameter out of the mold? Most 30 caliber GC shanks are .284, and they fit in a Sage GC fine. If yours are bigger, sounds like you are forcing the GC open more, which may or may not open evenly. Are you using his Gator checks?

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Originally Posted by PopcornSutton

What's the GC shank diameter out of the mold? Most 30 caliber GC shanks are .284, and they fit in a Sage GC fine. If yours are bigger, sounds like you are forcing the GC open more, which may or may not open evenly. Are you using his Gator checks?

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Nope, just the regular .30 caliber, copper, .017" thick gas checks. I haven't actually measured the boolit's shank, I'm brand-new to this whole gas check thing, so I'm still learning the ropes. I'll throw a caliper on the shanks tonight when I get home from work and report my findings.

In my research, I have recently found that .30 caliber gas checks are usually .320" in outer diameter, which should be plenty, even for a .303 British or 7.62x39 or 7.62x54R boolit, so it would make sense to design the boolit to use a regular .30 caliber gas check with a .284" diameter shank. After doing a little quick math, I have determined that a .017" thick, .320" outer diameter gas check should nominally have an inner diameter of .286". That should leave .001" on each side of a .284" shank for clearance, and sending it through the .314" sizer should allow the check to bite into the boolit shank by .002" on each side. ("should" being the operative word here) This is probably the case, but I'm still relatively new to casting my own boolits, and I think my mold is throwing the boolits a little bigger than .312". When I send them through the .314" sizer, it shaves a noticeable amount off the small tumble lube grooves on the boolit, so I guess the gas check shank could be a little bigger, too.



Anyway, we'll soon find out and go from there. See ya!

Scotty

Scotty: You really shouldn't be using a hammer to seat your gas checks - two reasons: first, the hammer blow could cause the nose of the bullet to expand. Even if this is only .001" to .002" it might make the bullets hard to chamber. Second, cast bullets are mostly lead, and can be bent easily. seating the checks on with a hammer could cause the bullet to bend like a banana. Even the tiniest bend in a bullet destroys the accuracy potential. It's better to try to press the checks on a tight bullet shank than to strike the bullet.

As a general rule, the harder the alloy the smaller the cast bullet's diameter. The difference in diameter between dead soft lead and a really hard alloy might be only .0015" or less, but harder is usually just a little (very little) bit smaller in diameter. Also, I've experienced such low quality with Lee molds that I've thrown all but one of my sets away. The problems that you're experiencing may not occur with molds from other manufacturers. Have you actually measured the diameter of the gas check shank on your bullets? Many people have experienced very good results from Lee molds, but I have had better results from other brands.

I suggest using a GC seater tool, instead of a hammer.

What JonB said, in spades.

OK, I measured a few boolits, and the shanks are all around .290", give or take 2 or 3 thousandths. I have discovered that a 9/32" socket, when twisted onto the shank, leaves the shank at a diameter that allows the gas check to slip on easily and straight, and still be crimped on squarely and securely by the sizer. It's a little tedious, but it solves the problem, and it didn't cost me a dime. Thanks for all the help.

Scotty

I use the NOE gas check expander, when needed. inexpensive tool, works well.

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Originally Posted by agcannon

I use the NOE gas check expander, when needed. inexpensive tool, works well.

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Which expander size do you use? .308'? What is the inside diameter of the gas check after you expand it using the expander tool?

Scotty

I occasionally use a hammer to seat stubborn gas checks. It's a small plastic hammer and I hold the bullet in my fingers. Rotating, while tapping. Use to use Hornady. Switched to Gator's, then Sage's. All fit about the same.

Winelover

Obviously the .312 bullet in the .314 sizer is not offering enough resistance during sizing, if any at all, for the ram to fully seat the GC. Try running the bullets through the sizer GC first with the nose on the ram.

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Originally Posted by Larry Gibson

Obviously the .312 bullet in the .314 sizer is not offering enough resistance during sizing, if any at all, for the ram to fully seat the GC. Try running the bullets through the sizer GC first with the nose on the ram.

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Hmmmmm. Ya know, this post makes me think. The mold I have drops the boolits wide enough that the .314" sizer is doing something. I sized all these boolits before I even thought about using gas checks. Could the process of pushing them through the sizer with no gas check have made the boolit shank expand a bit? That would be great, maybe my next batch will take the gas checks with no problems.

Scotty

I lay a flat piece of steel on top of the sizer to seat them and use the correct top punch to avoid distortion.
Then stand them up on the bench. They'll tell you if they aren't one square.
After that, they are ready to run through the sizer and be crimped on.

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Originally Posted by Winger Ed.

I lay a flat piece of steel on top of the sizer to seat them and use the correct top punch to avoid distortion.
Then stand them up on the bench. They'll tell you if they aren't one square.
After that, they are ready to run through the sizer and be crimped on.

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We're talking about oversized gas check shanks here, Winger.

Scotty

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Originally Posted by scottyp99

We're talking about oversized gas check shanks here, Winger.

Scotty

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Oppps. Sounds like a job for a BIG hammer.

LOL! I look at hammers the same way I look at golf clubs. If you want to hit the ball a certain distance, you pick a certain club. If you want to hit the ball farther, you don't swing the club harder, you use a bigger club. In the same way, you don't swing the hammer harder, you use a bigger hammer.

In this case, I have found a reasonably easy and simple (although tedious) way to bring the shank back down to a diameter that will allow the gas check to be easily installed in the conventional and proper way. I'm hoping that the original sizing operation (without gas checks) bulged out the gas check shank just enough to make gas check installation difficult, and that my next batch of boolits won't have this problem because I'll be applying the gas checks to an unsized boolit, and then sizing. Probably wishful thinking on my part, but hey, a man can dream.....a man can dream.

Scotty

30 cal expander. .284" I.D. after expanding. gator gas checks

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Originally Posted by agcannon

30 cal expander. .284" I.D. after expanding. gator gas checks

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Shouldn't they already be .284"? That is the nominal diameter of a .30 calliber boolit shank. I'm dealing with an over-sized boolit shank issue here, and the fix that I have come up with is to use a 9/32" socket to kind of swage the boolit shank back down to a size that allows the gas checks to slip on nice and easy, it's a little tedious but it works.

Scotty

Mine were measuring .277" id before expanding, kind of hard to measure the id with dial calipers. od before sizing .320". -.331" after sizing. I have it set up on a little lee single stage. Only time I've used it for 30 cal was when I tried powder coating before gas checking. lyman 311359 for a carbine. I just coat over the gas checks anymore. I use it mostly for a Lee 7mm mold I lapped out for my rolling block

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Originally Posted by agcannon

Mine were measuring .277" id before expanding, kind of hard to measure the id with dial calipers. od before sizing .320". -.331" after sizing. I have it set up on a little lee single stage. Only time I've used it for 30 cal was when I tried powder coating before gas checking. lyman 311359 for a carbine. I just coat over the gas checks anymore. I use it mostly for a Lee 7mm mold I lapped out for my rolling block

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I find it difficult to believe that the outside diameter of the gas check would increase .011" during the sizing operation, so I'm assuming you mean the expansion operation. Even then, it sounds a little odd that increasing the inside diameter by .007" increases the outside diameter by .011" (things don't always work the way we intuitively think they should work, eh?)

Anyway, I am brand-new to gas checks, and I feel like I have learned a lot just from this thread, so thanks everybody!

Scotty

I guess it's more a gas check flaring tool. What's the inside depth of you gas checks? measure and let me know. just trying to keep you from seating checks with a hammer

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Originally Posted by agcannon

I guess it's more a gas check flaring tool. What's the inside depth of you gas checks? measure and let me know. just trying to keep you from seating checks with a hammer

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The gas checks I received from Sage's Outdoors are .319" outer diameter, .283" inner diameter, and .056" in depth, as near as I can measure with a digital caliper.

Scotty

I would try an unsized bullet put the gas check and see if it works, I think larry hit on it, if the bullets are allready sized then there in no resistance to help get the gas check on.

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Originally Posted by redriverhunter

I would try an unsized bullet put the gas check and see if it works, I think larry hit on it, if the bullets are allready sized then there in no resistance to help get the gas check on.

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I'll try that with the next batch of boolits I cast up.

I think the problem I am experiencing now is gas check shanks that are too large. (the pressure from forcing them through the sizer might have smooshed the shank out a few thousandths of an inch wider?) The gas checks just won't go onto the boolit shank straight and square without pounding them on. When I reduce the shank diameter with my home made tool, they go on easily, nice and straight and square, and they crimp on just fine. It seems to work, but it's kinda tedious, that's all.

Scotty

I believe the gas check will get seated fully when the round is fired. As long as it's on there securely.

Even if it's not on there securely, it would probably be ok, but you can check this yourself. I had one bullet out of a batch where the gas check easily slid on/off after lubing and sizing. I was afraid it could fall off inside the case. To test this idea, I seated it in an empty case and then cut the case in two, right behind the bullet. At the proper seating depth, this left the gas check almost 100% protruding into the case... yet I couldn't pry the gas check off. So it must have been only 95% exposed.

After realizing the case will hold the check I loaded up a batch of unsized bullets with the gas check just placed over the shank without sizing/crimping it in place. The unsized gas check killed the neck tension, and the bullet would just pull out of the case if you unchambered the cartridge. But the gas check would still be in there, holding the powder in. It wasn't a big batch, but I didn't notice any difference in POI or accuracy.

GONRA sez - scottyp99 needs a decent MICROMETER to measure DIAMETERS.
Various calipers are great for LENGTHS.