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Thread: Pressure Question GC/PB

  1. #1
    Boolit Master

    TCLouis's Avatar
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    Pressure Question GC/PB

    I am addressing this to Larry Gibson since he is the only one here that has pressure measuring equipment (that I know of).

    Do you get any difference in pressure between gas checked and plain based boolits in the same loading?
    Nothing is impossible for the person that does not have to do it.

  2. #2
    Boolit Grand Master


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    That's a good question. I've not made that comparison. I could check my records but I hesitate to post any speculation based on comparing the pressure tests of different bullets probably conducted at different time/dates. The variables would be there and I'd get the usual raft of manure from the usual critics here.

    However, if someone has a mould with different cavities that casts the same bullet for use with and without a GC I could conduct a test. All that's needed would be a quantity of each cast of the same alloy. I would size, GC the ones for GCs and lube them for the test. Fifty of each would be sufficient for sighters/foulers and 3 ten shot test strings of each. Any takers?

    Are we talking rifle or handgun cartridges?
    Last edited by Larry Gibson; 09-10-2018 at 12:23 PM.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  3. #3
    Boolit Master

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    I would love to see that test with 30 cal and maybe a 357 or 41 mag. But, I do not have identical moulds other than the GC cut. I will be watching this thread.

  4. #4
    Boolit Master
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    I would be willing to supply some NOE 311299 PB, but the opposing GC bullets would be from a Lyman mould. Would they be close enough to get good data, or would the need to come from a combo mould?

  5. #5
    Boolit Grand Master


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    Ideally they should be from the same mould which was either lathe cut via the same program or with the same cherry with one cavity having the GC shank opened up to full diameter......that perhaps should satisfy the critics. I would suggest the test using your bullets would be valid if the same bullet/different mould bullets were cast of the same alloy from the same pot, had the same bearing length, the same nose diameter and the GC bullet was within 3 gr of the PB bullet?

    I can easily test the cast bullets any of these calibers; .224, 6mm, 25, 7mm, 30, 31, 8mm, 35 (35 Rem, 38 SPL or 357 Mag), 375, 44 and 45 (45 ACP, 45 Colt or 45-70).
    Last edited by Larry Gibson; 09-10-2018 at 03:43 PM.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  6. #6
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    JonB_in_Glencoe's Avatar
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    I have a couple 41 cal. Ranch Dog molds (by Lee) CTL411-255-RF and the TL411-255-RF
    If it matters? I use a aluminum GC with these, due to not being able to find 41 cal copper GCs that fit this design.

    PS, I believe Ranch Dog cut/bored the GC shank to PB, using molds from the same batch from Lee.
    ~~~~~~~~~~~~~~
    “If someone has a gun and is trying to kill you, it would be reasonable to shoot back with your own gun.”
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  7. #7
    Boolit Grand Master


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    Don't have a 41 caliber test barrel......sorry.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  8. #8
    Boolit Buddy Old Coot's Avatar
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    Larry,
    Why would it not be feasible and simpler to just check the pressure of a bullet with the gas check and without. The bullets would be the same, from the same mold, and of the same weight, within slight variation, and one lacking the gas check. The check itself would not weigh much, and if they are loaded to velocities less than 1500 fps should not lead the barrel. If you use bullets cast with and without a gas check, the base of the plain based bullet would up the weight by 2 to 5gr. (?) . Just my guess on that. ANyway I look forward to the results. Brodie

  9. #9
    Boolit Grand Master popper's Avatar
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    Can't imagine how there would be any difference. Added friction from GC might change the curve a tad. Same load density, same burn efficiency.
    Whatever!

  10. #10
    Boolit Master Bazoo's Avatar
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    Tagged with interest.

  11. #11
    Boolit Buddy Time Killer's Avatar
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    Larry I have one that I believe you are very familiar with the NOE 310-165-FN-H3 (30XCB). Its a 2 banger one gas check one plain base. If it will work how would you like them cast. I can do soft lead + tin for fill out, 50/50 soft lead / wheel weight + tin for fill out, or Wheel weight + tin if needed for fill out. Air cooled or water dropped let me know your preference. It will take me a few days to cast them as I have a busy work week but I would be happy to help out for the test. I also have the NOE TL311-166-RF-AI4 and the NOE 311-137-RF-CA3 if one of them will be better.
    Last edited by Time Killer; 09-10-2018 at 11:16 PM.

  12. #12
    Boolit Master

    Rcmaveric's Avatar
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    Tagged to follow. Wondered this myself. Maybe try a 35 cal plain based bullet vs a 35 cal plain based with a plain based gas check.

    Sent from my SM-G950U using Tapatalk
    "Speak softly and carry a big stick; you will go far."
    ~Theodore Roosevelt~

  13. #13
    Boolit Grand Master


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    Time Killer

    The 30 XCB, cast both PB and for a GC will work for me. TCLouis, the OP, didn't say whether he was inquiring about a rifle or handgun cartridge. If you can cast then of COWW + 2% tin alloy and air cool them it would be fine. With 100 of each I can test them over a classic Unique load of 10, 11 or 12 gr and over a bit more powerful load using H4895 and a Dacron filler.

    With an additional 30 of each I could also test them in in a pistol cartridge using the 32 H&R Contender barrel?
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  14. #14
    Boolit Grand Master


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    Old Coot

    I don't know if the results would be any different using a GC bullet with and without the GC(?). That remains to be seen. With the 30 XCB bullets from Time Killer I should be able to run at least a 10 shot test string of the GC XCBs w/o the GCs and get an idea?
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  15. #15
    Boolit Buddy Time Killer's Avatar
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    Larry I am draining and cleaning my pot tonight. I may even have time to get them cast depending on what the missis has planned.

  16. #16
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    My prediction is that the pressures will not show any statistical difference and within the realm of standard variance.

    Great test.

    Thank you for all involved especially Larry and Time Killer

  17. #17
    Moderator Emeritus

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    Subscribed. Results should be interesting. Semper Fi, Treetop
    "Treetop"
    Sgt. USMC
    1968-71

    "Accuracy has a suppressive power all by itself."
    Lt. Gen. George Flynn, USMC

    “The Second Amendment was not written to protect your right to shoot deer.
    It was written to protect your right to shoot tyrants…”
    Judge Andrew Napolitano

  18. #18
    Boolit Grand Master


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    Time Killer

    PM with address sent. No real hurry as the AC'd bullets need to age 2+ weeks anyway. Also will be out of the net hunting so I probably won't get the test done till next month.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  19. #19
    Boolit Grand Master

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    My vote is ....little or no difference.

    I have been wrong before so we shall see.
    Gary
    Certified Cajun
    Proud Member of The Basket of Deplorables

  20. #20
    Boolit Man
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    my guess ....

    with GC bullets, pressure increase will be 1-2% - velocity increase will be 1-2% - ES and SD will dramatically decrease - also (obviously) chance of leading will decrease.

    But, since we're talking more about pressures, I stick by my guess that GC bullets will tend to show a 1-2% increase in pressure compared to similar plain base bullets.

    Just my guess ....


    jd

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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