Case Length Question

Discussion in 'General Reloading' started by thaddy1978, Sep 24, 2010.

  1. thaddy1978

    thaddy1978 G&G Addict

    I have only been reloading for about 2 years...not near as long as some you, but I was thinking the other day about case length and have a newb question. How important are case trimmers? I can see, if I have brand new brass, I may want the case length to be close, but otherwise, what difference does it make? When making final adjustments for a full round, I am not measuring the case, its the OAL. Pressure would be the same, wouldn't it? The case may be a bit longer, but the bullet seats just as far as a properly trimmed case, right? I have a case trimmer for my 357 and have yet to use it. Can't seem to find one (at the moment) for my 303 Brit or 8mm Mauser. Your thoughts? I don't own semi-automatics (that I reload for anyway), so perhaps a slightly longer case may get caught up and jam? Hence the need for a case trim?
     
  2. Mooseman684

    Mooseman684 G&G Newbie

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    Thaddy , Thaddy...
    IF it wasnt important ,nobody would do it. Case length is Critical to NOT causing high pressures and / or Jamming up your gun. Go Back to your Handbook and READ that section again. Man, you are playing with 40 to 50 THOUSAND pounds of pressure in a controlled explosion...are your eyes and fingers worth trimming cases and doing things properly ? I hope so for your and the shooter next to you !
     

  3. Ten Man

    Ten Man G&G Evangelist

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    ^^ What he said. ^^
     
  4. lefty o

    lefty o G&G Evangelist

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    with bottleneck cartridges, trimming cases is pretty much a necessity. straight walled pistol casings never need it.
     
  5. Mooseman684

    Mooseman684 G&G Newbie

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    Really ???
    Then how are my .380acp , 9mm and .45ACP cases gonna headspace properly if they are too Long ???
     
  6. lefty o

    lefty o G&G Evangelist

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    straight walled pistol casings do not get longer when fired and reloaded, they actually get shorter. you will lose the case or crack the mouths before ever needing to trim them. the only time i would ever bother trimming a straigh walled pistol casing would be with the big thumpers like the .454, .475 linebaugh, 500s&w, and then they would only be trimmed so that i could put a heavy consistent crimp on them.
     
  7. thaddy1978

    thaddy1978 G&G Addict

    I do so apologize for the lame question...and yes, I do need to reread the section of my book and I shall. But I guess I question how it increases pressure? (I do have to dig my book out, as I have recently moved and have not unpacked everything yet). If a case is, let's say .02" over, I can see how that would potentially cause a jam, but pressure would remain the same in one trimmed properly. if the bullet is seated to the proper overall length, that excess brass would simply rise .02" higher up the bullet, making the bullet look like it was seated deeper, but when compared to a properly trimmed case and round, side-by-side, they both have the same OAL and the same amount of space below the bullet. I do understand fully, that excess space or too little from seating a bullet can cause havoc and be potentially deadly.

    I guess to further try to understand...I'll use my .357 for example--and just so everyone knows, I would never do this!!!! It's just to illustrate what I am trying to say, in order to understand more fully, based off your comments. I have a .38 special round with 3 gr of powder and a 158 gr rn. Would it yield the same pressure if I took a .357 round with the same 3 gr of powder and 158gr rn, but seated the bullet to match the .38 round? Same volume, isn't it? And in theory, the same pressure?
     
  8. Mooseman684

    Mooseman684 G&G Newbie

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    I disagree...My .45 acp cases , .30 carbine cases, and .44 mag cases as did my 45 colt cases when I shot them years ago all lengthened after several reloadings and had to be trimmed. Belling the mouth and crimping as well as firing works the brass and lengthens it...
     
  9. lefty o

    lefty o G&G Evangelist

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    thaddy , yes volume has something to do with pressures, but even with the same powder charge, you can get more pressure with the bullet seated out closer to the rifling.
     
  10. thaddy1978

    thaddy1978 G&G Addict

    Thanks Lefty, I understand. But Regardless (with the .357/.38 example), pressure would be the same because the bullets would be seated to the same OAL as each other. The 357 would essentially be a 38 spec. with a longer case. The bullet being seated closer to the rifling does in fact change the pressure, that point is clear to me...the volume changes. It won't change (regardless of case length) if they are both seated the same (per my example). Know what I mean?
     
  11. Mooseman684

    Mooseman684 G&G Newbie

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    Thaddy, a couple Thousandths in a REVOLVER might not make much of a difference ,as long as COAL is in spec, BUT in a Semi-auto Chamber you can get Major problems...
     
  12. thaddy1978

    thaddy1978 G&G Addict

    Yes, I could see it being more of an issue in a semi-automatic. But would the issue primarily be a chambering issue vs. a pressure issue? And yeah, I guess my whole point is so long as the COAL is in spec, pressure won't change...theoretically speaking.
     
    Last edited: Sep 24, 2010
  13. I guess one way to verify, and in the end, settle the disagreement, is, measure a .45acp case before shooting it and then measure it after words.

    To be honest, I didn't plan on trimming any of my handgun cases, semi-auto or revolver. When I got to reloading rifle, you betchya...
     
  14. Mooseman684

    Mooseman684 G&G Newbie

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    Many factors can affect pressure...temperature, the amount of Friction holding a bullet, the amount of crimp, the bullet material and size,primers, even the difference in powder batches can be 5%~10% IN PRESSURE.
     
  15. thaddy1978

    thaddy1978 G&G Addict

    Okay, I understand all of that, but all other things being the same, I am not going to lose an eye or finger or blow up the dude next to me by not using a case trimmer for my 357 given the COAL on a case that is over in length. I fully understand all of the other factors, it was simply the case trimming I was curious about with regards the volume not changing and thus pressure stays consistently in the normal safe range.
     
  16. Mooseman684

    Mooseman684 G&G Newbie

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    if your bullet is seated deeper in a longer than normal case, it could increase in pressure somewhat...Maybe Not Dangerous pressure , But I personally will NOT chance it at all. I am from the Old school of reloading, do it right and check it twice, for safety sake ! I load for accuracy so I want consistency in my cases, My bullets, and all the components...
     
  17. thaddy1978

    thaddy1978 G&G Addict

    I agree 100%. I like to load for accuracy too, it was more of a hypothetical inquiry. I have had so much brass, and have reloaded all of them maybe once (for the 357/38) that I simply haven't bothered to check case length yet. And I don't load heavy. As far as my example with the 357/38, I wouldn't do it either (as stated earlier), I don't like it if it ain't in the book. This was all something that I was just sitting here thinking about this evening while enjoying my quiet time with the wife and kids all asleep. :)
     
  18. samuel

    samuel G&G Newbie

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    The reason overlength necks can/will be dangerous is they get into the riflings/lands and make it impossible or at least very difficult for propper bullet release.If the bullet can't move,the pressure goes up until something moves.Usually there is about .002" or more for the neck to expand and free the bullet.If the neck is jammed into or unfolds into the riflings which are about .004" to .008"smaller diammeter.(Bore on .30 cal= .300",groove/bullet diammeter is .308") outside neck diammeter can be about .337" to .343" or so.If this is jammed/forced into a bore diammeter/groove diammeter of .300"/.308" there isn't any expansion to release bullet."KABOOM"!!! Also,it is the maximum OAL that you must "NEVER"excede.The trim to is to get all cases the same exact length for crimping.It is sloppy workmanship but if the length varies between max OAL and trim to it won't hurt unless crimping.Also,on handgun/straightwall cases they invaribly shorten when fired and usually stay shorter than max OAL because they expanded out making them shorter OAL and you can never get them back to original factory specs,thus leaving them shorter but if you are crimping,(all revolvers and some AL,s (pistols) they must be trimmed so the crimp is equal on all cartridges.If not trimmed even, the bullet will not be released the same on revolvers making for an accuracy problem and a headspace problem on AL,s(pistols) causing FTF/feeding/ accuracy problems.
     
    Last edited: Sep 24, 2010