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Thread: first casting for 7,5x55 swiss

  1. #1
    Boolit Buddy
    Join Date
    May 2013
    Posts
    122

    first casting for 7,5x55 swiss

    Sorry if I write in the wrong section, but I have some problems concerning both the merger and the gas checks.
    For the first time, I have made mergers for my k-31.
    I used the mold STAMPO DC CTL312-160-2R SKU: 90361 with G.C., alloy 90-5-5 at a temperature of about 350 C. (660 F ???)
    These are my questions:
    1) - I noticed that some balls have minimal irregularities as shown in the photos: can they be used or should they be refounded?



    2) - some g.c. are not held back (about 20% of boolits): what can be the cause? I used Aluminum coil, thickness 0.14.
    In all the other boolits, however, just scratch a little with my nail and the gas check is gone! Maybe they sold me too thin aluminum? I'm sorry because I bought it in England and I spent a lot!

    3) - some g.c. after being put on the boolit and crimped / calibrated (.308) it has a small part detected on the edge of the base, but so small that I can't photograph it. Go away by rubbing the base 2 or 3 times on abrasive paper. After they are perfect !!! What can be the reason?

    Last edited by airone46; 04-25-2020 at 04:08 PM.

  2. #2
    Boolit Grand Master
    Join Date
    Aug 2005
    Location
    South Jersey
    Posts
    5,556
    What can be the reason?
    Your melt and mold temperature is TOO low
    Kick the temps up to 730 F with a 5 second pour and the temp to frost the sprue puddle in 5 -10 seconds
    Your bullets will be B - E -A -U - T - I - F - U - L
    Regards
    John

  3. #3
    Boolit Buddy
    Join Date
    May 2013
    Posts
    122
    The biggest problem is that the G.C. they are not crimped well!
    Unfortunately I can't take good pictures!

  4. #4
    Boolit Buddy
    Join Date
    May 2013
    Posts
    122
    I think I posted in the wrong section, thanks to the computer's automatic translator (generally I leave in English and if there is something I don't understand I enter the translator in Italian! But I don't know why I inadvertently entered the automatic translation setting!)
    Change I section of my post?

  5. #5
    Boolit Grand Master

    swheeler's Avatar
    Join Date
    Mar 2005
    Location
    Montana
    Posts
    5,148
    Your mold temperature is too cold, maybe alloy temperature is too. It looks like your gas checks touch the top of the gas check shank on the bullet, and the bases with checks installed are concave, if so too large diameter of aluminum disc is being used, maybe too thin.
    Hell, I was there!

  6. #6
    Boolit Master
    Join Date
    Mar 2016
    Location
    SE MISSOURI
    Posts
    700
    I have shot bullets like this at 25 yards that shoot decent but you might get a few fliers. Yes to cold heat the pot up and the problems will go away

  7. #7
    Boolit Buddy
    Join Date
    May 2013
    Posts
    122
    Thanks for your interest in my problem!
    I used an analog thermometer from Lyman
    (I'm waiting for an infrared thermometer to arrive from China - will it work ??? - or to mount a PID). The melting temperature was about 350 C / 662 F . A 90-5-5 alloy melts at around 300 C: so I think it is reasonable to work at 350 C!
    Maybe I'll try to work with slightly higher temperatures: 735F / 390 C! I wait for the Chinese thermometer to arrive. I also wait for the heating elements to heat the mold to about 270 !
    The thickness of the sheet is what is recommended: 0.014. The basis of the boolit + g.c. it is perfectly flat. Only someone present a small wrinkle that disappears by rubbing the base against a piece of abrasive paper 2 or 3 times!
    Unfortunately it is the reflected light that gives this impression of concave bases!
    The biggest problem is that, as I have read in many posts, Lee makes the stem for the g.c. smaller than many other companies!
    As I said using a brass sheet the problem disappears! But brass is much harder to cut and more expensive!

  8. #8
    Boolit Master
    Join Date
    Apr 2017
    Location
    Minnesota
    Posts
    3,476
    Yes, try the 380-390 celcius range. That's where I get my best results with rifle bullets.

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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