Odd 41 mag gas check needed...

[mattw]

So, I cast a 230 LBT OGW bullet, the shank measures .3990 - .3995. I can barely force Sage's Lyman 41 check on this bullet. Does anyone know of a slightly larger 41 gas check?

[JonB_in_Glencoe]

There is like seven different 41 caliber GCs.
I have a 411-255-RF Ranch Dog mold (a custom Lee six cavity) in GC style, that has a unique shank size...I don't recall the exact details right now, but I had to have Sage's make a custom GC for it. They made several samples with different material thicknesses for me to test. I have no idea if he still does this type of thing for a customer?

If the GC you have is close enough, there are a couple of tricks you can try to make that one work.
1. Anneal the GC, makes the metal softer and it might squeeze on.
2. Make a tool to open up the GC, this can be done with the correct size steel ball bearing and brass hammer.
3. Cast the boolits with a Very Hot mold, especally keeping the sprue plate extra hot, so the boolits come out frosted and the Shank will be a bit smaller...I've done this with a Lyman mold, and you'll notice that the edges of the boolit bottom will be less sharp, but still will be uniform.

[mattw]

There is like seven different 41 caliber GCs.

If the GC you have is close enough, there are a couple of tricks you can try to make that one work.
1. Anneal the GC, makes the metal softer and it might squeeze on.
2. Make a tool to open up the GC, this can be done with the correct size steel ball bearing and brass hammer.
3. Cast the boolits with a Very Hot mold, especally keeping the sprue plate extra hot, so the boolits come out frosted and the Shank will be a bit smaller...I've done this with a Lyman mold, and you'll notice that the edges of the boolit bottom will be less sharp, but still will be uniform.

I am currently doing #2 with a modified (hand ground) punch. I am casting at 720, this is where the mould works well, never even gets frosty, but comes out clean. This is a tough mould to cast with and get no worm trails, takes lots of heat. I have been trying to call them this morning already, will keep trying.

[JonB_in_Glencoe]

Casting with a "Very Hot mold" is different that setting the furnace alloy temp to 720º.
It's about a casting rhythm and ambient air temp and air flow in your casting area.
The only real way to judge it, IMHO, is the level of frost on the boolit surface...Or a mold with a temp probe in it, which is something I've never tried, but I know others have.

[mattw]

I have never tried a mould probe either, I have a couple of blocks that are drilled for one. I like to go to a nice uniform light frost, do not want them to look textured as I think that is way to hot a mould for casting. If they are mirror like, I consider the mould to be a bit cool.

[JonB_in_Glencoe]

I do agree with that for most casting. I was just sharing a alternative casting technique to get a smaller GC shank.

[mattw]

I will give it a try in the next casting session... I just do not normally drive them up that high, personal thing I guess.

[megasupermagnum]

Have you tried a 44 caliber gas check?

[mattw]

I have not... I do not cast for anything 44.

[mac60]

I had a similar problem a while back. It wasn't .41 though, at any rate sage was able to hook me up with a different check that worked out much better. Did you email them and tell them your problem? Maybe they can help you. If all that doesn't appeal to you, it's a very simple matter to make a "punch" or expander to expand the check a little before you seat it - doesn't NOE sell such a thing?

[mattw]

Yup, made a punch, no machine tools so not high precision but works... I did talk to Al and he does have a cute little tool that will address the problem and it is not horribly expensive. Now all I have to do is find Lyman style 41 checks in stock somewhere. :)

[Minerat]

I have a MP 413640 it uses a 416 gater GC but my MP 411 hammer uses a standard 41 GC., maybe try the 416. Sage has them.

[mattw]

Al measured his assortment for me today, of the three common ones the lyman style is the largest. I have a call and email out to Sages. Did he get swamped in the gulf storms?

[TomAM]

44 mag GCs avarage .4015" ISM; that's only a couple thousandths larger than your shank.
You'd be swaging them down about .02 though. Their OSD is .433".

Lyman type is bound to be your best bet, once you've belled the mouth. They are .397 inside and .411 outside.

[mattw]

Yup, that is basically the measurement Al got. Thanks for the replies!

[hickfu]

I ran into the same issue this last month and used an arbor press from harbor freight to press them on with no problem.
just put the check on the bullet up-side-down and it takes little pressure to seat it with the arbor press.

[DukeInFlorida]

CALL Shamus Sage, and discuss your issue with him. He's a very knowledgeable guy and will offer you a perfect solution.

[mattw]

I was finally able to talk to Sage's today. I have the last 1k of the Lyman type checks on the way. Shamus told me that was the best option for this mould.

[Shamus]

The Gator brand .41 Lyman gas check is for a .397 shank size, its the largest of the .41's shank wise. Its a very thin gas check made from .007 gilding brass, so the tolerances are very tight.

You take the metal thickness, double it and add the shank size to get the overall diameter. So: .007 + .007 = .0014 + .397 shank and you get about a .411 O.D. You do have to figure in the height too, but that simple math gives you an idea of metal thickness needed.

A .284 30 cal shank works great around .015 in my opinion. Dad started out making .30's with Charlies' FreeChex tools using an Amerimax roof flashing that runs .0147. It's hard stuff, but made the gas checks the right size for the average .309 to .311 bullet. I still make my aluminum .30's using .015, but I buy the coils custom slit from annealed aluminum made for stamping.

Larry Blackmon, the Gator Gas Check guru, has been sending out samples of a thicker version of .41 Lyman. I think it was made using .010 and so far feedback is good. My .41 Lyman mold drops .398 shanks and likes the thicker metal version better. I don't know what it would do on a .399 to .400. A .44 gas check is for a .402 shank, but the Gator .44 and Hornady checks are made using .017 thick gilding brass. So, much larger O.D. than a .41 would need.