Gas Check Expander

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I’m using the 22 sharpshooter gas check maker to make some aluminum gas checks. I have the NOE gas check seating die but the gas checks the die makes are smaller than Hornady 30 Cal gas checks and won’t fit on the shank of my 300blk lead Taco GC bullets.

I was going to purchase the gas check expander but I’m not sure if I need the 308Cal GC Expander Ram or the 284Cal GC Expander Ram because the shank size on my bullets is .283″-.287″

If the 284Cal GC expander ram expands the inside diameter of the gas check to .284″ then that will be perfect for me. I measure the inside diameter of Hornady 30 cal gas checks to be .2835″.

The 22 sharpshooter gas check maker I have produces gas checks with an internal diameter of .2715″ which is problematic and seems like a bad design. IF I force them onto the shank they swage the base of the bullet or they mushroom out and fall off. Annealing them helps a bit, but they are extremtly difficult to get started on the base of the bullet without them seating skew and just compressing the rim of the gas check.

• This topic was modified 2 years, 11 months ago by kentfielddude.
• This topic was modified 2 years, 11 months ago by kentfielddude.

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[Mike B.Moderator]

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I originally had the same question…

The long & short of it is go with the GC Shank diameter…  That is what the Gas Check inside cup dimension is…  For verification please look at the attached reference for gas check dimensions.

https://www.tmtpages.com/draw/HelpfilesBas-5/hs160.htm

I tend to think that the attached reference intel will be of use to you…

Take Care, & Stay Safe…

 

[kentfielddudeParticipant]

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So the 308 cal gas check expander is for 30 cal bullets?

• This reply was modified 2 years, 11 months ago by kentfielddude.

[Mike B.Moderator]

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As I said originally … if you look at the B dimension on the TMT design reference chart… you will see that the inside B dimension cup size for a 30 caliber gas check is basically approximately the shank size of .284. In this case the 32 caliber / 8mm Gas Check is approximately  .301 -.303 … Thus a .308 B dimension cup size … would tend to be the appropriate diameter dimension for the 32 Caliber … 8mm manufactured gas check  The gas check expander diameter that you appear to need is the B dimension on the TMT chart that you are looking for… If you use a 308 caliber expander mandrel on a manufactured 30 caliber gas check you may tend to completely flatten out your manufactured aluminum gas check pocket rather than just expanding the gas check’s B dimension from your  approximate .2715  to basically .284 … In any case is would not tend to sit flat on the NOE expander to do the job that you want it to do…

In every case that I have used the .284 expander for the 30 caliber gas checks. You see the 30 caliber  gas checks have to basically fit flat on top of the expander to be opened up correctly… Otherwise you may find that the gas check is flattened out once again once you place it on the expander punch and expand it.

I have a rather large number of the NOE GC expanders in my war bag, & in every case I utilize the B dimension size on the TMT dimension reference chart to properly select the proper size of the B dimension cup size for the expander that I need  … The NOE dimension nomenclature appears to be the inside cup size for the GC … in this instance… not the dimensioned GC size …

If you study the GC shank sizes you may tend to note that the shank size dimension tends to be basically be in most cases one caliber shank size smaller than the next caliber cast size…

This is to in one sense of the word … To allow the thickness of the material (.010 — .017) material thickness … that the GC is made from … to fill out the GC shank gap … on the GC shank to bring it up to the needed GC caliber size… once tightly fastened on to your cast product… You may need to potentially also look at the thickness of the material that you are using to make your aluminum 30 caliber gas checks… a thicker material will affect the inside bend dimensions measured… a thicker material may just end to produce a different size B dimension.  Nuff said on that subject … lest this reply turn into a metal bending college thesis…

I sincerely hope that this rather long winded shank size intel is a bit clearer now… once again you might wish to take a screen shot of the referenced TMT GC dimensions for reference down the line…

https://www.tmtpages.com/draw/HelpfilesBas-5/hs160.htm

Take Care, & Stay Safe…

[kentfielddudeParticipant]

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I tried both 0.4mm and 0.5mm alumnium sheet to use to make my gas checks. Both produced gas checks with same ID, and OD. Only difference is height of the gas checks. The 0.5mm material has so far produced better gas checks than the 0.4mm alumnium.

 

I think you mean’t to say the 32cal/mm is .303 B dimension?

• This reply was modified 2 years, 10 months ago by kentfielddude.

[Mike B.Moderator]

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You are correct that the diameter of the B dimension in the portion of the modified posting that you added about 1.5 hours afterwards…  The fact that the .5 MM tends to produce a better gas check is most probably because it is ~ .019 thick… that is also most probably may just be the reason that your B dimensions are closer to ~ .271 instead of .284 as would normally be expected with a thinner gas check the .4 MM material is ~ .0157 or .016 …  diameter…  If you looked at the TMT reference that I added and look at the B dimension I believe that you will want to get the NOE GC expander that measures .284 … As that is what I use to expand the 30 caliber gas checks either in Copper or Aluminum … When I need to … modify the GC’s either in Al or Cu…  You will want to set your manufactured GC as flat as you can on the .284 shell holder expander ram … before running your single stage press up to against the expand the lips of your GC cup…  & in your case the GC cup dimension to something closer to the desired .284 shank diameter…

I recently tried to get the Sharpshooter GC maker to respond to my initial query on a slightly different detail… so that I could hopefully & potentially ask some more questions to try to get some additional intel on that GC makers design … So far no luck on that portion of the equation… I sincerely wish you luck in trying to expand the .271 B cup to a .284 B cup… It will be interesting to hear back from you once you down the line on your endeavor…

If I do get some more intel on the original GC tool makers design … I will try to pass it on to you down the line…  I currently do something similar with the .410 B dimension GC’s to expand them to .417 for one of my design applications  which needs a .417 B cup dimension …  Nuff said on that …

You do know that you can also do a private message to me … by logging in and after selecting my name select a private message or a public message… maybe that will allow me to send you a dwg or two as the public message appears at the moment to be blocking all attachments …

Take Care, & Stay Safe…

 

[kentfielddudeParticipant]

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I placed an order for the .284 gc expander. I’ll make another post once I try it out but it will be a while as I won’t be home for another 7 weeks.

I tried to make a post with some embed images and I click submit, seems like it went through but then I don’t see my rely. Also tried adding an embedded link and the post also doesn’t show up. Just pasting link url seems to work though.

View post on imgur.com

• This reply was modified 2 years, 10 months ago by kentfielddude.
• This reply was modified 2 years, 10 months ago by kentfielddude.

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