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Old June 22, 2011, 01:13 PM   #1
TennJed
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cartridge deminsions/minimums

where can i find info on the minimum lenghts for a loaded cartridge (all would be nice but specifcally 38sp). this is assuming the printed info in my manuals (ex lymans) is for the maximum. i loaded my first batch of rounds and they are measuring well below the printed ex i have
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Old June 22, 2011, 01:50 PM   #2
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AFAIK, dimensional data doesn't include "minimum OAL".

The OAL shown is a suggested length for that bullet, sometimes governed by magazine dimensions or the location of the cannelure on the bullet.

For rifle cartridges, "seating to 0.010" from the lands" is a common practice, with a variety of tools available to assist in determining this dimension. However, sometimes the cartridge won't fit in the magazine when it is seated for this depth and the shooter is forced to decide if he wants to shoot those accurate rounds one at a time...

The best I can offer is to pull them all and reseat them to the correct length shown for that bullet.

While .38 Special isn't known as a high pressure round subject to all kinds of mayhem from bullet setback, it isn't a good idea to seat bullets deeper than the data shows.
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Old June 22, 2011, 02:17 PM   #3
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Generally speaking he deeper the bullet is seated the higher the pressure will be for any cartridge. And the closer the bullet is seated to the lands the more accurate the round should be. Thus minimums are of little interest. The goal should be to seat as long as possible for a given bullet. Again this, like most things, doesn’t always hold true, but usually does.
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Old June 22, 2011, 04:17 PM   #4
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Lee loading manual states minimum OAL for all it's loads.
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Old June 22, 2011, 04:39 PM   #5
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That's for pressure. SAMMI gives a maximum COL just to ensure magazine fit. No minimums. You can't predict a minimum without knowing the specific components and powder charge.

Pressure goes up both as you seat deeper, because less room is available for the powder to burn in, and as you near the throat because less gas can bypass the bullet before it obturates (seals off) the bore. Most accuracy buffs tend toward seating long, but it doesn't always work. Berger used to recommend kissing the lands with their VLD's, like the old benchrest method, on the assumption it was best. However, they also had a lot of reports from people whose guns just refused to shoot well with them. Subsequently they learned their bullets actually do best in bands of seating depth about 0.030" wide, but which may be centered anywhere from about 0.030" to 0.150" off the lands. A letter on this from Berger is here.

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Old June 22, 2011, 04:46 PM   #6
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If you are loading a revolver caliber like .38 Special with real revolver bullets having a cannelure or crimp groove, you cannot go far wrong by seating to and crimping in the groove. This pretty well determines the OAL and it will nearly always be ok for a load in the standard range given in the book.

Rifle bullets should be seated so you can load the magazine if you wish to shoot as a repeater. This will normally keep your bullets from jamming into the rifling. If you are firing single shot, you need to control seating to give the appropriate jump to the rifling. Which is determined by shooting for accuracy.

Autopistols are the most sensitive to seating depth/OAL. Go by the book if you have one with a "recipe" FOR THAT EXACT BULLET. If not, the way to start is to load as long as the magazine and chamber will accept.
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Old June 22, 2011, 07:16 PM   #7
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ok here is what i got...maybe i am reading something wrong ...or maybe my cases are too short

lymans list the 38sp as 1.550 from bottom to bullet tip...case 1.155

mine are measuring about 1.433...case is 1.149

before seating the bullet measures .527....it is a 125 gr berry's 38 caliber product #95022....plated (no cannalure).....which berry's website does list this bullet as a 38 special

i would have to almost not seat this bullet at all to keep it at 1.550

so what are your opinions on this
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Old June 22, 2011, 08:55 PM   #8
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What's going on here (I believe) is that your Lyman data is showing typical COL for .38 Special RN (round nose) bullets.

Your Berry's 95022 is a FP design. Same bullet weight in a shorter profile.

You really can't compare COL data between different bullet types.

Generally, if you can't find load data specific to your bullet, you can find a similar weight/profile bullet by another manufacturer and substitute that data.

Following my own advice, Sierra's manual shows a COL of 1.450" for a 125gr JSP bullet with a profile that looks similar to the Berry's FP. Your 1.433" is close.
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Old June 22, 2011, 09:54 PM   #9
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The SAAMI drawing says the case is 1.155" +0/-0.020". So it is to be between 1.135" and 1.155" long.
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Old June 22, 2011, 11:31 PM   #10
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thanks!
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Old June 23, 2011, 06:01 AM   #11
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Might look in here and see if you find anything that will help.

http://www.saami.org/specifications_...tion/index.cfm


I hope the link comes through...
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Old June 23, 2011, 09:02 AM   #12
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Nick's #5 chart is interesting but it may be a bit misleading. I mean, it's based on an established load (.30-06, 150 gr RN, 53/4064) and then only the seating depth is changed starting from lands contact, which then gives the low pressure point at about .25" off the lands. IF the loader develops his charge at the OAL he seeks, no matter how close to the lands, there will be no pressure "spike" so long as he stays there. (I hate that term "spike" as if it's something spooky, all chamber pressure is in the form of a timeressure spike, our job is to keep it normal.)
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