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Thread: Seating to crimp groove vs powder charge

  1. #1
    Boolit Buddy
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    Seating to crimp groove vs powder charge

    Going by hodgdons online data for Tightgroup, I find I must seat bullets .100 deeper to get the case mouth to the crimp groove. That's a lot less space in the case. Data says 3.2-3.8grs with a coal 1.475. Thoughts? Will I increase pressure too much by seating to groove? I had charged the cases with 3.4gr but I may dump and go 3.2.
    Click image for larger version. 

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  2. #2
    Boolit Master
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    357mag or 38spl?
    I'm a big fan of data-driven decisions. You want to make me smile, show me a spreadsheet! Extra points for graphs and best-fit predictive equations.

  3. #3
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    Quote Originally Posted by Daekar View Post
    357mag or 38spl?
    Oops. 38spl.

  4. #4
    Boolit Master
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    It appears that the data on the Hodgdon site is for a LSWC and you might be loading a RFN cast bullet. Since the bullets are not the same, the crimp groove is not likely in the same location. But this shows why it is suggested that you start at the suggested starting load and work up from there. Are you one to take a chance or are you more likely to set these cartridges aside in a well marked baggie and start at 3.2 gr and see how they do before increasing the charge since you seated the bullet deeper.

  5. #5
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    Who is the manufacturer of you bullet or mold, and what is the manufacturer’s part number?
    *
    What is the total length of your bullet?
    *
    What is your final overall cartridge length?

  6. #6
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    It would be reasonable to measure from the base of the bullet to the lube groove and determine if the case volume is the same if seated to the crimp groove. However, the book data will not show that. So back to start at the beginning and work up as safety indicates. The book data establishes what was used to develop the safe limits and are intended to be a guide.

  7. #7
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    Quote Originally Posted by Dusty Bannister View Post
    It appears that the data on the Hodgdon site is for a LSWC and you might be loading a RFN cast bullet. Since the bullets are not the same, the crimp groove is not likely in the same location. But this shows why it is suggested that you start at the suggested starting load and work up from there. Are you one to take a chance or are you more likely to set these cartridges aside in a well marked baggie and start at 3.2 gr and see how they do before increasing the charge since you seated the bullet deeper.
    Only one made up is the one in pic. And it's seated per suggested oal.

  8. #8
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    Quote Originally Posted by justindad View Post
    Who is the manufacturer of you bullet or mold, and what is the manufacturer’s part number?
    *
    What is the total length of your bullet?
    *
    What is your final overall cartridge length?
    Lee 358-158-RF
    Coated length is .635
    Have not seated to groove yet but would roughly be 1.375ish to groove

  9. #9
    Boolit Master
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    Then that makes it a lot easier to begin again. Good luck and see what you can determine and update the thread.

  10. #10
    Boolit Master
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    My recommendation is to seat to the OACL shown in a load manual, and taper crimp like a bottom feeder cartridge - maybe someone else will comment if this is or is not a good way to go.
    *
    The Lyman Cast Bullet Manual (4th Ed) has the Lyman 358665 158 grain RFN bullet seated to an OACL of 1.445”, and the starting & max loads of Titegroup are 2.9-3.3 grains. The Hodgkin data has the bullet approximately 0.030” farther out of the case and the charges are up to 0.5 grains higher. So if you now seat your bullet 0.070” deeper than the Lyman data, you would have to drop the charges even further.
    *
    Load manuals don’t always agree and I don’t know how long the bullet was that Hodgkin used (I also don’t know how long the Lyman bullet is), so I don’t know how much the pressure would increase if you started at 2.9 grains and seated to the crimp groove - might not make for a good day at the range.
    I could be wrong - it happens at least daily.

  11. #11
    Boolit Master

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    I was going to suggest a Lee collet crimp die because they will crimp anywhere on the bullet, but then I didn't really recall seeing one for 38spl. I searched in the usual places for a 38spl collet crimp die but came up short except for this listing: https://www.cheaperthandirt.com/lee-...307908133.html

    Must be a mis-print because I do not see how it could work on drastically different case lengths. Although I wouldn't be afraid to shorten a 357 collet die to work with 38spl. They are cheap enough that if I screwed it up on my bench grinder I'd just shrug my shoulders and toss it and my idea in the trash can.
    Last edited by oley55; 09-26-2022 at 11:53 AM.
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  12. #12
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    .1" isn't that big of a deal in .38 Special. In 9mm sure, but I wouldn't worry about it here.

    When it comes to pressure in pistol cartridges the exact OAL isn't as important as how much of the bullet is seated in the case. For a 148 grn wadcutter 3.3 grains is the max and the entire bullet is seated inside the case. 3.4 grains with the bullet shown will be fine.

  13. #13
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    ".1" isn't that big of a deal in .38 Special. In 9mm sure, but I wouldn't worry about it here."

    Could be famous last words......

    I don't know about Titegroup powder in the 38 SPL case as I've not pressure tested that combination. I have, on the other hand, pressure tested 5 gr of Green Dot in the 357 Magnum under the TL358-158-SWC seated to different depths. A change in seating depth of .1 from an oal of 1.582 down to 1.482 result in the average psi going from 23,900 to 32,500. that's an increase of 8,600 psi for that .1" deeper seated bullet. In a 357 Magnum revolver both loads were still "safe". However, in a 38 SPL to be used in a 38 SPL firearm that kind of increase in psi could prove not good.
    Larry Gibson

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  14. #14
    Boolit Grand Master uscra112's Avatar
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    Listen to Larry.

    What counts is not the OAL but the seating depth, i.e. position of the base of the bullet relative to the case mouth. Ignore OAL entirely, as any spec given is only valid for one specific bullet.

    Figure out your seating depth and post it; maybe one of us can help you. Also measure from the base of the bullet to the crimp groove with a caliper and post that.
    Cognitive Dissident

  15. #15
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    3.2gr titegroup seated to groove chronographed 799.2 in my Smith 64 with a 4" bbl. and ejected just fine but it was only one. Base to top of groove is .356. case depth with caliper is .983 or so.
    Click image for larger version. 

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    Hodgdon shows 815fps in their data for 3.2 titegroup 158 LSWC

  16. #16
    Boolit Grand Master uscra112's Avatar
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    OK, set up a Quickload model with that data, and the predicted velocity is pretty close to what you got. Calculated pressure is ~12.5k psi, which makes it a fairly mild load. If you're happy, stick with it. You've got about .5 grain headroom if you want to go faster, before you get into the red zone.
    Cognitive Dissident

  17. #17
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    Quote Originally Posted by brokeasajoke View Post
    Oops. 38spl.
    That's a big roomy case with a very compact powder. you could seat a full wadcutter and not cause any problems with decreased space.

  18. #18
    Boolit Grand Master uscra112's Avatar
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    Wad cutters seated full depth would require a much smaller powder charge.

    I loaded 2.0 grains of Bullseye for my Officers' Model Colt, for a 147 grain full wadcutter seated flush. Titegroup would be the same or 0.1 grains less.

    n.b. My most accurate wadcutter load actually seated the bullet about .200" out of the case, which let me go up to 3.0 grains. Same pressure. Had I tried 3 grains with the wadcutter seated flush, I probably would have ruined the gun. QL calculates P=36.6kpsi. That's how sensitive the .38 can be to seating depth.
    Cognitive Dissident

  19. #19
    Boolit Master


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    Quote Originally Posted by uscra112 View Post
    Wad cutters seated full depth would require a much smaller powder charge.

    I loaded 2.0 grains of Bullseye for my Officers' Model Colt, for a 147 grain full wadcutter seated flush. Titegroup would be the same or 0.1 grains less.

    n.b. My most accurate wadcutter load actually seated the bullet about .200" out of the case, which let me go up to 3.0 grains. Same pressure. Had I tried 3 grains with the wadcutter seated flush, I probably would have ruined the gun. QL calculates P=36.6kpsi. That's how sensitive the .38 can be to seating depth.
    I load a 148gr hornady 10208 (hbwc) 2.7 - 3.3 gr. titegroup

    Plenty of room.... and that's a straight hodgdon recipe...

  20. #20
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    Quote Originally Posted by uscra112 View Post
    OK, set up a Quickload model with that data, and the predicted velocity is pretty close to what you got. Calculated pressure is ~12.5k psi, which makes it a fairly mild load. If you're happy, stick with it. You've got about .5 grain headroom if you want to go faster, before you get into the red zone.
    I'm not after hot rodding the 38spl. I have a 357mag if I want to go faster with the same bullet. These are just plinkers.

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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