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Thread: GC or flat bottom??

  1. #1
    Boolit Master
    nekshot's Avatar
    Join Date
    Nov 2008

    GC or flat bottom??

    I love PC! Now that is established but I still can not decide if a GC is "really" needed for accuracy or a nice flat bottom? Any pearls of wisdom on that side of the boolit? I am referring to 1700 to 2200 fps delivery.
    Look twice, shoot once.

  2. #2
    Boolit Master Reddirt62's Avatar
    Join Date
    Mar 2017
    Oklahoma City
    Well, call me paranoid, but I still gc my coated 454 Casull boolits.

    Sent from my SM-N920V using Tapatalk

  3. #3
    Boolit Master popper's Avatar
    Join Date
    Jun 2011
    I use a 145gr PB in BO @ >2K fps. I barely can control the base flatness without adding an unlevel PC to the base. I cast some, changed my sprue cut timing and got non-flat bases. Target with those shows an almost perfect circle @ 100. PCd base can have same effect. GC or not is up to you, haven't tried PB in 308W yet but 30/30 & 308MX give same results PB & PC. PC is not a GC.

  4. #4

    Mind sharing your BO load?


  5. #5
    Boolit Master
    Dragonheart's Avatar
    Join Date
    Jan 2012
    Katy, Texas
    As far as protecting the base of the bullet from the short duration of extreme heat and gas cutting at high velocity the PC will do that. However, to achieve the best accuracy I believe a gas check is the best alternative if it is set absolutely flat and completely uniform. PC will improve the imperfections in the base of a cast bullet, but the bullet's base will never be as perfect as that can be made using a GC.

  6. #6
    Boolit Master

    Lloyd Smale's Avatar
    Join Date
    Mar 2005
    munising Michigan
    if your looking for the absolute best accuracy a bullet will deliver if its a gas check use gas checks. If you don't want to use gas checks buy plain base molds. If leading is your only concern then you can probably coat and not check.
    Soldier of God, sixgun junky, Retired electrical lineman. My office was a 100 feet in the air, closer to God the better

  7. #7
    Boolit Master

    blikseme300's Avatar
    Join Date
    Mar 2009
    Deep South Texas, RGV
    Flat bases with and without GC's are always needed for accuracy. GC designs PC'd but with no GC have always done poorly for me.

    If care is not taken a GC can be flat but off-square and this will degrade accuracy. Goodsteel did an interesting experiment some time ago that went into this in depth. I need to find his post and link it here.

    As for the need of GC's at higher velocities in my limited experience it depends. My experience has been that with 30cal no matter the alloy with and without PC that GC's are needed for accuracy above around 1,600fps. Others probably do better than this but I have not experimented more but simply use GC's for higher velocity.

    With 500gn PB and GC'd CB's PC'd through a Ruger M77 458WM I had very little difference in accuracy at between 1,800 & 2,000fps. The CB's where PC'd using shake&bake and set on their bases before baking. The CB's used were cast from the same mold but one cavity was modified to remove the GC step to become a PB.

    My guess is that there is a relationship between the base area and the pressure that allows the larger calibers of CB's to work fine without GC'c at higher velocities than compared to smaller calibers.

    I am still learning so this hobby stays fun.
    Liberalism is the triumph of emotion over intellect, but masquerading as the reverse.

    I don't know how we ever shot maximum loads before P/C come along and saved us all. R5R

    "No mosque in the United States flies an American flag."

  8. #8
    Boolit Master popper's Avatar
    Join Date
    Jun 2011
    Bluejay - 31-142C, isocore(96/3/1) with Sn replaced with Cu, ESPC. PC wiped from base, WD after 1/2 hr bake on hot plate. 16.5gr. H110, 18" 1:10 McGowan SS barrel/carbine gas. Avg 2112 ES 47 RCBS powder dropper/ not trickled - Lee die and FCD. Sized 3085. On a rare day I get < MOA @100.

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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