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Thread: burnt case mouth

  1. #1
    Boolit Mold
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    burnt case mouth

    Hi board, I have about a 100 paper patch rds down range, so I don't know much! This morning I fired 24 rds of O.E. 1 1/2,69 grs, 370 Buffalo bullet, PP to .401, in a Shilo Sharps .40-65, compressed .050, .030 card wad, OL 3.236, bullet in case .125, case as fired ,no crimp. Vel was in low 1400s.200 m/m ,6#MVA. Wind was terrible, gusting to 30 MPH, from 7 oclock. So group was horizontal, about 8in.My question is the cases had a scorch mark about the depth of the seated bullet. It will come off in the ceramic tumblr.Just wondering what caused this as it doesn't happen with Swiss 1 1/2.Also when depriming cs the punch was covered in (goo) ?,which also doesn't happen with Swiss. thanks binski

  2. #2
    Boolit Master
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    The burnt residue on the case mouth is from an inadequate seal which allows pressure to leak past the case mouth back toward the case head. Annealing might make it go away. Sometimes it just seems to be due to a powder with a lower burn rate.

    Chris.

  3. #3
    Boolit Grand Master
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    binski - burnt case mouths is called blow back. As Chris stated, with black powder reloads there a 2 primary reasons: (1) Cases not sealed to the chamber walls - anneal your brass to a blue/green color = 650 degrees and (2) low powder charges reloading heavier bullets
    Regards
    John

  4. #4
    Boolit Master

    rfd's Avatar
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    i think the chamber also matters, as those with a throat or freebore for lubed groove sized bullets allow added room when using bore size paper patch slicks that's harder to seal off the gases.

  5. #5
    Boolit Buddy dave roelle's Avatar
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    You might size a few 45-70 cases of differing manufacturers and see what the case thickness at the mouth is. The thicker the case wall ,to a degree, could take up the excess space in the standard chamber giving a quicker seal.
    Be sure to trim to fit the chamber length and anneal the cases.

    Works in my roller using starline cases

    Dave

  6. #6
    Boolit Grand Master Don McDowell's Avatar
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    Little more compression will change that. Excessive fouling such as your getting is usually a sign that the powder needs more compression.
    GUSA #6
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    But People will NEVER forget how you made them feel

    Want to join in adult conversation about shooting the old ways without the hysterics associated with other places?http://historicshooting.com/mybb/index.php

  7. #7
    Boolit Mold
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    I will try to anneal some cases, as the ones I'm using have never been annealed, and go with more compression. Got more PP bullets coming from Buffalo. In the meantime, I"ll shoot some smokeless PP I"ve wanting to try. binski

  8. #8
    Boolit Master

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    i had a roller and its grease groove chamber had a goodly throat/freebore. it was not meant for bore rider PPBs, but i entered into patching with that gun and would get blow back around the case because the bullets were .4495" in diameter and not .459". the gun and cartridge was very accurate, and i only load with real black powder. but if there's room at the case mouth in the chamber, and the cartridge is a smaller diameter, it won't seal well ... but it might be be better if the brass is annealed. in the long run, that gun now sports a true PPB chamber and there are no blow back issues, and brass does not require annealing. but it can never again shoot greasers.

  9. #9
    Boolit Buddy
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    binski,
    You might want to try a DDEPP bullet: DualDiameterEllipticalPP such as mine
    in your 16 twist 40-65.
    Load : 371 gr DDEPP over 74.5 gr Swiss 1.5/0.060 LDPE wad,Fed 150 LP primer
    It is stabile out to 1K. See PIC for 100yds group and of bullet and load

    Click image for larger version. 

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  10. #10
    Boolit Buddy
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    Note that the bullet has a base band that patches up to FF case I.D./Freebore
    and body that patches up to bore dia for perfect concentricity
    beltfed/arnie

  11. #11
    Boolit Buddy
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    My load goes just over ACTUAL 1400fps over my Oehler Chrono
    from my 30" barreled HiWall
    beltfed/arnie

  12. #12
    Boolit Buddy dave roelle's Avatar
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    Nice looking bullet beltfed

    Dave

  13. #13
    Boolit Master
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    Before I switched over to just shooting muzzle loaders, my mentor, who had won many matches and makes a pretty bullet lube told me what to do. First you have to waste some lead (not perfect bullets) and powder and fire form the cases. Next clean them in Dawn and water, then use a ceramic tumbler to get them sparkling. Next square the edge of the case mouth and match all case lengths exactly. Next just before loading use an expander and bell the case mouth very slightly and try them to see what the seal will be like. He used a seater tool which I made a copy of (and are for sale on the ASSRA website) to push them the final 1/16 inch or so. Set the expander die so all will be the same amount of bell. Finally do the loading, powder compression, ETC, ETC.


    I know this is what you already do anyways but I wanted to show where belling the case mouth fits in. I never annealed any cases and my mentor never did either.
    John

  14. #14
    Boolit Buddy
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    Quote Originally Posted by beltfed View Post
    binski,
    You might want to try a DDEPP bullet: DualDiameterEllipticalPP such as mine
    in your 16 twist 40-65.
    Load : 371 gr DDEPP over 74.5 gr Swiss 1.5/0.060 LDPE wad,Fed 150 LP primer
    It is stabile out to 1K. See PIC for 100yds group and of bullet and load

    Click image for larger version. 

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    Nice shooting! Are you wet or dry patching those two diameter pills.
    Thanks, Richard

  15. #15
    Boolit Buddy
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    I get that little fowling at the end of my cases also. I am shooting pp out of a gg chamber but I have hardly any freebore. It used to bother my but I have gotten used to it


    Sent from my iPhone using Tapatalk

  16. #16
    Boolit Buddy
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    . So here are 2 cases. One was sized at the moth and the other was not. This darkening isnít apparent until sometime after the case has been fired.


    Sent from my iPhone using Tapatalk

  17. #17
    Boolit Master

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    yup, that's what happens with a PPB bore rider in GG chamber, no sealing. yers looks lots worse than mine was. are you annealing the brass?

    if you really only wanna load and shoot PPB's, yer chamber can be drilled, sleeved, and properly recut with a rented PPB reamer. i had that done to a pair of rifles and the result were just excellent in every way. however, those guns can't ever load GG cartridges, which is just fine by me. ymmv.

  18. #18
    Boolit Buddy
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    burnt case mouth

    I do Anneal after each firing. Those were very early in my paper patch trials and for whatever reason they arnt as bad now but they still do it. Itís not real apparent when they are first fired but the next day is usually when they are black like that. To be honest with you I have been more than happy with the performance of my standard chamber and my bore diameter bullets. When I call up c sharps and get another rifle I will want the same chamber design which is just a standard Sami spec chamber.


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  19. #19
    Boolit Master

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    if a day later yer cases look like those images you posted, so yer not cleaning the brass ASAP?

  20. #20
    Boolit Buddy
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    Nah. Sometimes I donít drop them into a bucket of water until the next day. When Iím at a match I just donít feel like de priming then and doing all that while I am trying to stay focused for the shoot.


    Sent from my iPhone using Tapatalk

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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