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Thread: Aluminium gas check failure

  1. #21
    Boolit Buddy Silver Eagle's Avatar
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    Might want to also check the dies in the check maker. Depending on how one is making the checks it could make a huge difference. Is the check maker first punching out a disk and then forming it into a cup? Or, is it doing it all in one step? I used to work QA on terminals formed on high speed presses. The reason that the punch and form steps were performed in a certain order was mainly to eliminate material failures. Having not seen how commercial checks (or yours) are made I cannot give a comparison to the processes.
    The alloy of the aluminum would also have some affects, as different alloys have different machining / forming characteristics.
    Can you post some pics of the checks in various stage of making?
    Silver Eagle

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  2. #22
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    Look at the punch or mandrell in the die. If it is to flat or the edge to sharp it will cause gaps in the skirt of the Check or fractures. Yesterday we ran 37,000 checks with copper. Switched over to aluminum ran a 1000 or more when the sound of the press changed. Stopped and found the damage checks with gaps in the skirt on ever other check. Checked with Charley he agreed the mandrel needed some work. Put it in the drill press and spun it lightly with 220 sand paper for 10 t0 15 seconds holding finger pressure lightly at about 30 degrees from perpendicular. Polish with fine rubbing compound. Go slow and try it often. Ran 31,000 aluminum checks with no problems. Going to have a Big Sale real soon!

  3. #23
    Boolit Master



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    Quote Originally Posted by Sagebrush7 View Post
    Look at the punch or mandrell in the die. If it is to flat or the edge to sharp it will cause gaps in the skirt of the Check or fractures. Yesterday we ran 37,000 checks with copper. Switched over to aluminum ran a 1000 or more when the sound of the press changed. Stopped and found the damage checks with gaps in the skirt on ever other check. Checked with Charley he agreed the mandrel needed some work. Put it in the drill press and spun it lightly with 220 sand paper for 10 t0 15 seconds holding finger pressure lightly at about 30 degrees from perpendicular. Polish with fine rubbing compound. Go slow and try it often. Ran 31,000 aluminum checks with no problems. Going to have a Big Sale real soon!
    Bring it on buddy!
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  4. #24
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    Quote Originally Posted by mac60 View Post
    Bring it on buddy!

  5. #25
    Boolit Buddy
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    You may want to try annealing the Al strip before forming checks. Forming sheets puts a lot of stress in the Al and forming check even more which can create small cracks or forming lines that fail on firing. Just a thought.

  6. #26
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    If the OPs gas checks are coming from a Freechex tool set, call Charlie Darnell, and mention loose checks. He will likely get to reduce the diameter of the punch in the tool set. That will make the checks much much tighter. Mine always stay on the boolit, right up to the target, with very high precision.

    The tools are press fit assembled, and the punch is your problem. It sizes the inside of the check.


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  7. #27
    Boolit Master Retumbo's Avatar
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    Easiest thing to try first is use thicker material.

  8. #28
    Boolit Buddy andrew375's Avatar
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    SUCCESS!! Following on from my earlier post regarding the edges being cracked and torn during the cupping operation, I opened up the blanking / forming punch (the OD cuts the disk, the ID pushes the edge of the disk down around the cupping punch) by 8 thou'. I did this by centring the punch in a 4 jaw chuck, so I would be keeping the bore concentric, and then used a boring bar. With .016" material the checks came out perfect except slightly "open" indicating the punch bore was slightly too big. With .020" material the checks came out as they should, with parallel sides and no signs of tearing.

    I tested 5 of each check. With both the checks were firmly fixed on to the bullet base. I loaded them in front of 56 gr. of VV N140 (for around 2200fps) with an extra 3 rounds with Hornady checks as a reference. Shooting at 50 metres with a front rest , but no sling or jacket, the 3 Hornady checked bullets went in to 1/2" centre to centre. The five with the 20 thou' checks went into the same place, opening the group out to just over an inch (blame the nut behind the trigger). The of the 5 with the 16 thou' checks the first two went about 4 inches below the above group and the last three back in aforesaid group. So I am well happy.

    Also, there were no gas checks on the range floor, so they obviously stayed on.

    So thank you everyone, we got there in the end and it was you who gave me the clues that put me on the right path.
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  9. #29
    Boolit Grand Master

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  10. #30
    In Remembrance

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    As a further followup to this discussion, I'd point out that increasing the gas check raw material only works up to the point where the gap between the punch and the die equal the material thickness. After that, you are just extruding the gas check "wall" longer and longer. The real fix is usually to, as the OP did in this instance, open up the die diameter. Leave the punch alone, since that still needs to fit tightly on the bullet shank.

    Charlie Darnell walked me through this years ago, when I needed a gas check that would work equally well on a .500 Magnum, and on a .50 Beowulf boolit. The barrel of the .50 Beowulf needed a slightly larger gas check. So, using Charlie's suggested technique of attaching some 1000 grit emery cloth to a wood dowel, adding some oil to the cloth, and spinning it inside the disassembled die, I was able to open up the outside diameter of the gas check while leaving the inside the same.

    Used two different sizing dies (.501" for the 500 magnum and .503" for the Beowulf), and was able to properly install the same gas check (used .024" raw material) on both boolits.

    In the opinion of most of us, the gas check, when properly installed, should not fall off easily with fingernail effort. It should actually end up slightly "crimped" in place, and stay on the base of the boolit for the entire journey to the target. They should not need super glue or any type of adhesive to keep them in place.

    I'm shooting 429-215 Lyman boolits (210 grain RFN) in the LawnSteel game. And I am pleased when we reset the steel targets and I see all the shiny gas checks on the ground, just in front of the struck steel targets. I know they did their job.


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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