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Thread: case length

  1. #1
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    Default case length

    What to do with cases that dont measure up to at least trim length. Isort my cases by head stamp and length so that they are all the same . I have beleaved that the bullet should be as close to the throat of the barrel without touching or being forced against or to far away. My thought is the bullet should be captured by the troat or rifling long before it leaves the case to achieve max accuracy and be consistant. For example when using a new style bullet i will seat to crimp grove than chamber it to check fit. Any input on this ?.

  2. #2
    Dogs Like Him versifier's Avatar
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    Conventional wisdom tells us that a bullet should be seated to at least one diameter within the case. However, as long as there is sufficient bearing surface of bullet within the case neck that the bullet is firmly enough held so that it does not move and effect the concentricity of the cartridge and enters the bore straight with its axis parellel to the bore, it generally makes no real difference if the case is a bit short. But, if there is a roll or taper crimp involved, and there are other cases in the batch that are the full correct length, then there will potentially be problems as the crimp will not be consistant from round to round. If a collet (factory) crimp or no crimp at all is used then it is often a non-issue.

    In many magazine fed actions, the OAL is limited by the physical dimensions of the mag itself, so it is difficult if not impossible to seat the bullet out so far that it is unstable. With some though, including single shots and actions with long throated chambers, especially if boat tailed or light-for-caliber bullets are used, occasionally you can run out of sufficient bearing surface and be unable to seat them out as far as you might like without difficulties. Some actions simply will not feed cartridges longer than factory spec, leaving you with the option of single loading them if you want to use longer rounds.
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  3. #3

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    Beyond whatever Versifier said, the cases will stretch after a bit and won't be short. For practical purposes, you won't notice enough difference to be concerned, unless you're trying to put all of the bullets into one tiny hole.
    Tom

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  4. #4
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    Just trying to achieve the best accurate and consistant loads that I can. Somewhat of a perfectionist I guess. When I think about it it really doesnt seem like a slightly lighter crimp would make a difference in pressure when you consider what the pressure is because of a shorter case but that is a [?] in my mind and the OAL [the distance from bullet to throat] also. I read where shooters are getting tite groups @ 100 yards and that is what i am trying to get. And I understand that a bullet needs the right amount of pressure from ignition to lvg the muzzle to achieve this goal also. Thats why rifle powders burn slower because of barrel length right ?.

  5. #5
    Wise
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    "And I understand that a bullet needs the right amount of pressure from ignition to lvg the muzzle to achieve this goal also. Thats why rifle powders burn slower because of barrel length right?"

    The length of the barrel does not make a powder burn slower or faster. The various powders have a specified burning rate depending on the cartridge. A powder could be too fast or too slow. Using the .308 Win. as one example, Bullseye powder would be way too fast except for some very special use as in making a gallery load, and might even be too fast for that purpose. It's a powder used for light target loads in handguns for the most part. You could use somethng like IMR 7828 in the .308 but it would be way too slow burning for that cartridge as it's used in the larger magnum rifle cartridges for the most part.
    Where the length of the barrel plays a part is it allows one to get the most bang for the buck when using the slower burning powders. I have several rifles in .308 and three have to use a powder normally not considered usable for the cartridge. A wierd situation that took a bit over two years to make the first rifle give a usable accuracy. All three rifles are the same make chambered to the .308 and only one set off components will work in them. groups are usable at 1.50" and that's the best those guns will do. All I know is I was able to buy three rifles cheap because their previous owners couldn't make them shoot tiny groups. A 1.5" group is more than adequate for a hunting round and I have taken deer out to 250 yards with those rifles.
    There is a simple solution to your brass that's a bit too short. Find the shortest one and trim the rest to match.
    You didn't say what round you were loading but if it's a big game hunting round, just how much accuracy does one need? It's great to sit down at the bench and shoot a teeny-tiny groups but out in the field, there are no bench rests. If you're shooting varmints, then really tight groups are more important but most varmint rifles I've owned were tight groupers to begin with. My Kimber .223 will keep 10 shots under a dime from the bench at 100 yards. I have one .308 that will consistanly shoot .375" to .50" groups all day long. Got very lucky with that rifle. I'm quite happy if my .416 Rigby does 2" at 50 yards. After all it's something to use up close and personal on stuff that has the intention of harming my tender body.
    I guess the point I'm trying to make is some guns never will be capable of .25" groups no matter what what you do. Enjoy them for what they are capable of doing.
    Paul B.
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  6. #6
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    Thanks for all that. Yes I know that the barrel does not make the powder slower or faster.

  7. #7
    runfiverun runfiverun's Avatar
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    the question was about the powder.
    i'll answer it this way.
    powder burns and creates gas the more powder you can use the more gas is made.
    the issue is pressure you are limited by the gun the case and common sense.
    now a slower powder will allow more gas volume to be made by delaying the peak pressure,which allows the bullet to be further away creating more room for the gas to fill as pressure rises.
    this helps keep pressures down because the bullet get's further away as the pressure tries to keep on rising.
    what it does is creates greater gas volume,a longer burn time [more time pushing the bullet down the bbl] and generally lower pressures.
    now the rub against all this great news.
    powders need a certain pressure window to burn effectively [efficiently].
    going too slow will lower pressure and leave unburnt or partially burned powder in the case/bbl which will of course lower velocity once again.

  8. #8
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    YES Thank you very well said thats what i was getting @ would it be correct to further say thats why you cant find data for some powders in certain calibers or cases because there is'nt sufficient space in the case.

  9. #9
    runfiverun runfiverun's Avatar
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    that's exactly why you won't find data for the super slow powders in many/most rifle cases.
    and the same reason why you don't have a load for bullseye for your 300 wiin mag.

    there are some conditions and exceptions that will allow you to use just about anything anywhere but you really are out on your own when doing that stuff.
    i have used 5 grs of bullseye in a rifle case before.
    and i have used super slow powders before but both were in cast bullet loads and i didn't want 2700 fps from either one of them.

  10. #10
    runfiverun runfiverun's Avatar
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    the slow powders like h-50bmg in your 308 will not get enough pressure built up to burn efficiently partially because it burns too slow and the bullet is gone before it can reach the 55-k it needs to rapidly consume itself.
    the bullet also doesn't offer enough resistance for the powder to have to work enough to get really going.
    and the ignition is inefficient because of the coatings on the powder itself.
    if you were to help the powder get going it would increase the efficiency and using a 38" bbl would also help.
    but you are starting into extremes where you still have no advantage over a 22" bbl and a faster [normal for caliber] easily ignited powder in either velocity or accuracy.

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