Gas Checks,Alum VS Copper

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  • Last Post 28 April 2013
Wayne S posted this 20 March 2013

 Did the search thing and couldn't find any direct comparisons of Alum.vs copper GC's.  Soooo, has anyone done a direct accuracy  test between both types  ???  Gator Checks in 22 & 30 seam to be non existent,  so I'm looking for other options

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onondaga posted this 20 March 2013

http://www.castbulletassoc.org/view_user.php?id=3610>Wayne S:

I have used high volumes of Hornady, Gator copper checks and Aluminum checks from our member here Sagesoutdoors.com. I find no difference in results. Early on I had read that Aluminum checks may leave aluminum fouling in chrome lined bores but I have proven to my satisfaction after thousands of rounds,  that is false and the Aluminum checks do not foul chrome lined bores with Aluminum and those negative comments about Aluminum checks came from a person with a conflict of interest who stood to gain financially from reducing the sales of Aluminum checks.

Gary

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JeffinNZ posted this 20 March 2013

I have done a lot of research work on gas checks over the last couple of years and have come to the conclusion that when making your own from alum. it is best to use material of at least 3xxx series. Lithography plate is good. Most flashing material is 1xxx series and more a lot of applications is too soft.

Cheers from New Zealand

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Pigslayer posted this 20 March 2013

I've been using AL checks from sages outdoors for a while now and find that they work just as well as copper. James Sage is a great guy to deal with & stands behind his products.

Pat

If someone else had of done to me what I did to myself . . . I'd have killed him. Humility is an asset. Heh - heh.

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Wayne S posted this 21 March 2013

Thank you all,  Pat, do the Sage  checks have the  “crimp-on” barb on the inside or just straight sides like the Lyman, I should say the OLD lyman GC ??

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onondaga posted this 21 March 2013

http://www.castbulletassoc.org/view_user.php?id=3610>Wayne S:

I'll grab that question with a picture

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tturner53 posted this 21 March 2013

JeffinNZ wrote: I have done a lot of research work on gas checks over the last couple of years and have come to the conclusion that when making your own from alum. it is best to use material of at least 3xxx series. Lithography plate is good. Most flashing material is 1xxx series and more a lot of applications is too soft.I'm just starting with home made aluminium checks. I have high hopes as I received a free Freechex II in .357 and have a large stash of rolled aluminum flashing. When you say “too soft” I can understand that, but what is the effect on performance? Fouling? Inaccuracy? I'm thinking it's gotta handle pressure better than a plain base at least. I will go ahead with my trials with .357 Magnum 1894c Marlin and .35 Remington Marlin 336 but am interested in what the softer (free for me) flashing has done for others. Heck, people double up beer can material.

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onondaga posted this 21 March 2013

http://www.castbulletassoc.org/view_user.php?id=2514>tturner53:

I've read the opposite about the aluminum for checks that softer is better.  I've seen annealing recommended for aluminum to make the cutting and forming easier on the tools. Just try what aluminum you have , if the thickness is near the upper limit for your tool and the aluminum is too hard, it is going to crack and tear.

Gary

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rmrix posted this 21 March 2013

This is an interesting topic for me to learn from.

I have been unable to get a good cooper GC fit on some of the shanks of my various  25 cal bullets used in 25-20Win-'92. So I gave James Sage's product a try. Not knowing he had choices in thickness and shank size I just ordered the stock offering. The first bunch that came fit one mould but not the others and he and I talked about fit via email.

James went far out of his way to get me a bunch of sample checks of various size and long story short, through trial application, I now have a source of checks for all the various bullets in 25 I play with in this rifle and now know what to order next time.

In my very limited testing I believe the aluminum checks provide as much accuracy as I can discriminate from the test rifle. In other words, I think they are fine for what I am doing.

I think it would take a very accurate bench rifle and known load to see how cooper v aluminum compare.    

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onondaga posted this 21 March 2013

Another tip I've read is that even if you have just the right design thickness to fit your tool and your bullet shank size that you can end up with checks that are loose if the aluminum is too hard. This happens because the harder aluminum has more spring back after the checks installed to the bases of your bullets.

That is the worst I've heard about making your own checks and the cure is simple. You take the strips you've cut  for your tool, hold one with a tweezers and run it through the flame of a torch or your kitchen stove gas burner. This will draw the temper from the aluminum so it will have less spring back after installing the checks and they will be tighter.

Gary

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JeffinNZ posted this 22 March 2013

There are a couple of critical factors when making and using GC's.

1) The GC must be made to fit the shank and the material must fill the void between shank and final sizing diameter. Formula is T = (SD - ShD)/2 where T is the minimum thickness of the material, SD is the sizing diameter and ShD is the shank diameter.

Eg: T = (.314 - .284)/2 T = .030/2 T = .015

Given the above I would be inclined to find some .016 material to ensure a good form and fit.

2) The material must be suitable for the use. Charlie of Freechex has found that very soft (eg: 1XXX series) alum with gall a die and I have found that soft alum (eg: deodorant cans) does not shoot accurately. Lithography plate in NZ is 3XXX series and works VERY well as does a batch of 3XXX series ribbon I bought from Yonky in the UK.

Hope this helps. YMMV.

Cheers from New Zealand

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delmarskid1 posted this 22 March 2013

I have been using painted aluminum flashing with good results. It is about .014” I have coils of the stuff Jeff mentioned from Yonky. I haven't tried it yet but it looks good. I haven't done side by side testing but I really can't tell the difference between copper and aluminum in my rifles. I've shot long strings of the home-mades through a couple of self-loaders and they work fine for me.

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daboone posted this 22 March 2013

Lithography plate, OK for those of us unenlightening where you you find/get this material? I did a google search and came up with wholesale suppliers which would be a little over kill for my meagre needs. :-)

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onondaga posted this 22 March 2013

http://www.castbulletassoc.org/view_user.php?id=2344>daboone:

Litho plates? the best price for those is from a dumpster behind a print shop, or ask the receptionist.

Gary

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JeffinNZ posted this 22 March 2013

Yes, litho plate is dirt cheap at the scrap dealer. I bought a sheet that would be 8 square feet for $3.00. Worked out it would make 10000 checks!

Cheers from New Zealand

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tturner53 posted this 12 April 2013

Range tested comparison loads yesterday with alum. vs. copper gas checks in a Marlin 1894c .357 Magnum. Identical loads using Lee 158 SWC/A2400. They shot the same. I got a Freechex II and will be going thru my .35s checking out the home made checks. I'd like to really push this bullet in a .35 Rem. Marlin 336, we'll see.  EDIT; The aluminum came from .011” rolled flashing.

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tturner53 posted this 27 April 2013

More tests comparing copper vs. aluminium gas checks; yesterday I shot the same loads as above in my 6” S&W M19, Lee C358-158 SWC over full charge of A2400. I couldn't tell any difference in the groups or anything else. These loads really have some snap, much more than my usual stuff, but I wanted a test. Clean load, no unusual fouling. Accuracy was as good as I can hold off bags using factory sights, easy 2” for 6 both at 25 yds. My conclusion is aluminium gas checks are aok, but you have to really be motivated to make them. I'd like another Freechex II in .30 cal. just for the peace of mind of knowing it's there.

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ubetcha posted this 27 April 2013

There was a debate on Cast Boolit site about the possiblity of bore damage caused by the possible presence of aluminum oxide on the sheet stock.Some claim that it is so minute that it shouldn't matter and some say they would never use aluminum checks. I'm still waiting for my 44cal checkmaker from Patmarlin to try aluminum checks.

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RicinYakima posted this 28 April 2013

It is probably not worse than the silicon dioxide used in the primers. WFIW, Ric

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RicinYakima posted this 28 April 2013

It is probably not worse than the silicon dioxide used in the primers. WFIW, Ric

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Webley posted this 28 April 2013

If the aluminum was oxidized, I think that it would be worse that any material in the primer as the gas check would be in contact with the bore. Aluminum oxide is very abrasive.

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RicinYakima posted this 28 April 2013

There isn't any “non-oxidized aluminum” unless it was coated from formation. Aluminum oxidizes in 30 seconds upon exposure to air unless coated.

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onondaga posted this 28 April 2013

If the Si02 forms at all,   it is an oxide layer at the molecular level and not a particulate abrasive. This is the typical misinformation you will run into on the internet from competitors with a vested commercial conflict of interest.

That conflict of interest nonsense would be rare to originate in this Cast Bullet Association Inc. Forum but is commonplace  on the other forum mentioned.

Gary

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Webley posted this 28 April 2013

Depends on the alloys. Yes, on pure aluminum, the oxide forms quickly, though as Gary mentioned, it usually stops at the surface level. Alclad skins have a pure aluminum layer over the high strength aluminum alloys for this reason. Otherwise a suitable conversion coating is used, such as alodine or anodize. I work at a large aircraft manufacturer and have seen my share of corroded aluminum. I do not know what alloy flashing is, so my thoughts should be taken with a grain of salt. (Pun intended).

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