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Thread: Copper Vs. Aluminum Gas Checks

  1. #1
    Boolit Master smokeywolf's Avatar
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    Copper Vs. Aluminum Gas Checks

    Has anyone noticed or done any tests with ballistic differences between copper and aluminum gas checks?

    Given that there is notable difference in the coefficient of friction of copper versus aluminum, does this manifest itself in the ballistic profile of say a 30-30 or 30-06 boolit?

    Anybody chronographed identical loads and components with the exception of changing only the gas check from copper to aluminum (or visa versa)?

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  2. #2
    Boolit Master

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    I have fired factory checks, and now produce my own aluminum checks. I cant tell the difference between the two. I can say there is a noticeable difference between regular plain based boolits and the same boolit with a plain based gas check. Those are made out of soda can material and swage right on the base during sizing. Check out the 'mother of all' link from PatMarlins as there are comparisons and photographs of dies, checks, boolits, and targets.

    As I understand things, copper and aluminum can be hard or soft depending upon its composition and treatment. I am using Amerimax aluminum flashing to make my regular checks and am quite pleased. Since i will never buy factory checks again, there will be no further comparison. My loads will be based upon aluminum from here on out. Switching from copper to aluminum shouldn't be treated any differently than switching from one factory brand check to another. Work up a load with your components and tweak as necessary.
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  3. #3
    Boolit Master
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    I have experienced very little velocity differences in identical loads, but have noticed an accuracy "shift" so to speak, as I got into the higher pressures with my .308win target rifle.

    Around the 2400 fps range (311299), the aluminum gas checks didnt group as well as the Hornady copper gas checks. Roughly double the group size at 100.

    When I switched to my Freechex II brass gas checks (.015"), my accuracy returned. BUT, with identical loading components, I lost about 50fps with the brass gas checks.

    With all things considered, I dont see "ANY" reason not to make/use aluminum gas checks.
    The velocities at which "my" target rifle shoots the aluminum gaschecked boolets accurately, is more than adequate for most of my needs.

    Enjoy the Aluminum gas checks!

  4. #4
    Boolit Master
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    I'd liken such a comparison as asking if one can detect the difference between a plutonium device and a hydrogen bomb at ground zero.

  5. #5
    Boolit Master
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    The OP asked if anyone tested to see if there was any difference.
    I did, and the information was shared.
    If a shooter actually does the shooting, like I did, you see some interesting trends.
    This "specific" test was with 1 rifle, so it is based on a large amount of shooting on a single source test subject.
    This is the best I could do, concidering I work for a living, and cant afford the time and additional rifles for such a test.

    The results/information stand. Use as you like to, but they are very accurately collected, and proscessed.

  6. #6
    Boolit Bub
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    Guess that all depends on whether you are striving for accuracy or just making noise.

    Quote Originally Posted by Jumptrap View Post
    I'd liken such a comparison as asking if one can detect the difference between a plutonium device and a hydrogen bomb at ground zero.

  7. #7
    Boolit Master JIMinPHX's Avatar
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    When I did back to back tests in a .30-30, they both performed about the same. Somewhere on this board is a thread where I posted pictures.

    I ran into trouble with aluminum checks when I tried to fire them out of a chromed barrel. I got terrible fouling that was VERY hard to clean out. I was making my aluminum checks out of aluminum Bud Lite beer bottles.
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    Boolit Master
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    All my fouling problems are with SS barrels. I think is just a fact of shooting SS guns. -tj

  9. #9
    Boolit Master
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    I've never used alum. checks but my concern would be galling, with both CM and SS barrels.

  10. #10
    Boolit Bub
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    i have used the alum checks on my cast 303 bullets and find them very good. my load is medium and the metal targets at 100 yds fall with no problem with leading. up here in canada i have noticed that the price of copper checks has gone way up so the price of the alum looks a lot better.

  11. #11
    Boolit Master Leadforbrains's Avatar
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    Is there any chance of fouling in a SS barrel with lower velocity loads such as the .357 magnum? That would be with the aluminum gaschecks.
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  12. #12
    Boolit Mold Shamus's Avatar
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    Aluminum checks can be made from many things that are not ideal. The common roof flashing shoots very clean, the .014 is very popular for .30. Same goes for copper, you want to use the right alloy. We tried using soft copper, didn't work well.

  13. #13
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    I've done several side by side comparisons between Hornady GCs, Blammer's GCs, aluminum GCs (.014 Amerimax flashing) and my own brass .014 GCs. My tests involved 2 different cast bullets (311466 and 311299) in 10 and 12" twist rifles measuring velocity and pressure (Oehler M43).

    As did Dthunter I found that at higher velocities the accuracy with the aluminum GCs deteriorated rapidly well before the commercial or my own brass GCs did. This occured in both twist barrels. I found no measurable difference between velocities or pressures other than the usual expected differences between test strings.

    While I use aluminum GCs I do not use them for higher velocity rifle loads.

    Larry Gibson

  14. #14
    Boolit Buddy 45-70marlin's Avatar
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    Larry, what do you consider high velocity? I bought a 1000 of them and will use on a 45-70 300 gr. bullet at around 1400 to 1800 fps.
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  15. #15
    Boolit Master


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    Quote Originally Posted by 45-70marlin View Post
    Larry, what do you consider high velocity? I bought a 1000 of them and will use on a 45-70 300 gr. bullet at around 1400 to 1800 fps.
    2000+ fps with the twist rate and accelleration rate seeming to be determining factors also. I use a lot of .014 Aluminum GCs myself for my 1700-1900 fps loads. I just quit using them over 2000 fps because of the "iffy". I know some will say they used thousands of them with no problems and that's fine with me, good for them. I haven't had such good use above 2000 fps and I've tried a couple different "lots" of aluminum flashing. Just my experience with them is all. If they work for you above 2000 fps then great but they don't always work for me above that.......I could anneal them or go through some other gyrations with them but "cheap" then doesn't become worth it to me. The brass GC's always work; commercial and my own........

    Larry Gibson

  16. #16
    Boolit Bub
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    I was wanting to cast for my mini-14, all of the information I found warned against it because of leading in the gas chamber. But I am one that has to see to believe! The trick was to have high enough pressure to make it cycle but low enough not to shoot lead powder out the barrel. I couldn't get high enough pressure with aluminum and it was right on the edge with copper. I started using soup can lids they are steel and tin, they mic and weigh the same as the lyman copper GC but are a lot harder. They seat very nice and you can find them down range still attached to the mushroomed lead. We were getting velocities of 2900fps at 100 yds 4" groups with both a mini-14 and an AR-15. All my relatives save me can lids, I smash them flat and cut into strips.
    I have but one friend, I trust in only myself and the Great Spirit, No woman can own me, but only fell the touch of my hand, I Lust for my freedom, and Love only my desires in life! 1989BKH

  17. #17
    Boolit Master
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    Lyon Co. Brass shim stock in 5 or 8 foot rolls, 6 inches wide, thickness of .001-.020 runs about $25-$30.

    .008 or .009 seems perfect for the 22. tj

  18. #18
    Boolit Master Von Gruff's Avatar
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    Agree with Larry's findings with the al gc seeming to top out around the 1900-2000fps range. I also did extensive testing with al in various thickness from .006 , .012, .018 (.012+.006) and .024 (2x.012) and they all started opening up groups past 2000fpr where the Hornady cu GC ran comfortably to 2415fps x 5 shots groups in the 1 1/4 range at 100yds for the 160gn CB in my 9 in twist 7x57. Have some .021 copper flashing that after annealing will make cheap GC and also give exceptable hunting accuracy at the same velocity, so I am not tied to the factory offerings.
    Von Gruff.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check