Maximum SAAMI overall cartridge length
- Thread starter RayB
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243winxb
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Headspace is different then OAL. http://www.saami.org/specifications_and_information/index.cfm?page=CC There is a tool to find the OAL and check head to datum. http://www.brownells.com/.aspx/lid=...g_Success___Minimum_Headspace_and_Maximum_COL
They deem the "standard maximum over all length" but that can be exceeded. Two particular cartridges that come to mind are the 257 roberts using 120 grain bullets and the 7mm WSM using 160 grain and heavier grain bullets. Both rounds are considered short action rounds and SAAMI list there lengths as such, but both rounds are often chambered for long actions to seat the long bullets out further so the bullets don't go deeper than the base of the neck. If you load them long like that they won't fit in a short action magazine.
Reloadron
Contributing Member
Using the 308 Winchester as an example the cartridge length is pretty much gospel. Note in the link the upper drawing is the cartridge and the lower drawing is the chamber specifications. With a focus on SAAMI and only SAAMI, discounting any custom chambers, we can see how things are designed to "fit".
The headspace is actually a chamber dimension, however, in the interest of simplicity we can apply it to a cartridge and define it as cartridge headspace dimension. Keep in mind we are only looking at cartridge dimensions, less a bullet, so not COAL or COL (Cartridge Overall Length). There are gauges to measure cartridge headspace, some are simple Go/NoGo and some are capable of giving actual dimension numbers. This old thread covers a few examples of case gauges. The bullets are taken into consideration where their ogive begins. This becomes a measurement of cartridge base to bullet ogive.
Hope that helps....
Ron
The headspace is actually a chamber dimension, however, in the interest of simplicity we can apply it to a cartridge and define it as cartridge headspace dimension. Keep in mind we are only looking at cartridge dimensions, less a bullet, so not COAL or COL (Cartridge Overall Length). There are gauges to measure cartridge headspace, some are simple Go/NoGo and some are capable of giving actual dimension numbers. This old thread covers a few examples of case gauges. The bullets are taken into consideration where their ogive begins. This becomes a measurement of cartridge base to bullet ogive.
Hope that helps....
Ron
ReloaderFred
Member
SAAMI specifications were developed to standardize manufacturing processes in the firearms industry. It simply says that there are standards for minimum and maximum measurements for cartridges, chambers and barrels.
The Over All Length (OAL) was pretty much set for magazine lengths and to a certain degree, chamber leades, though there is a lot of variation in the latter. For that matter, there is a lot of variation in magazine measurements, too, but at least there is a "standard" for both. If there weren't standards, you wouldn't be able to buy factory ammunition and expect it to chamber in your factory firearms.... Especially if the ammunition was one brand, and the firearm another.
Hope this helps.
Fred
The Over All Length (OAL) was pretty much set for magazine lengths and to a certain degree, chamber leades, though there is a lot of variation in the latter. For that matter, there is a lot of variation in magazine measurements, too, but at least there is a "standard" for both. If there weren't standards, you wouldn't be able to buy factory ammunition and expect it to chamber in your factory firearms.... Especially if the ammunition was one brand, and the firearm another.
Hope this helps.
Fred
Headspace measurement differs between rounds but its not how far the bullet has to move. In the case of the .308 its measured from a standard datum line on shoulder to the base of the cartridge. The neck and OAL have nothing to do with it.
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Has nothing to do with it. Did you read the linked material 243winxb linked to?
This might help a little.
http://www.thehighroad.org/showthread.php?t=734058
rcmodel
Member in memoriam
SAAMI MAX length has more to do with fitting every magazine then fitting every chamber with every bullet shape.
And it is totally dependent on bullet shape.
Looking at the 7mm RemMag for instance.
Hornady shows:
154 grain SST Spitzer = 3.290" COL.
154 grain Round Nose = 3.190" COL.
This is because the RN full dimeter bullet shank extends nearly to the nose of the bullet.
And if it were seated to SAAMI Max length, it would be jammed tight into the rifling leade on many rifles.
rc
And it is totally dependent on bullet shape.
Looking at the 7mm RemMag for instance.
Hornady shows:
154 grain SST Spitzer = 3.290" COL.
154 grain Round Nose = 3.190" COL.
This is because the RN full dimeter bullet shank extends nearly to the nose of the bullet.
And if it were seated to SAAMI Max length, it would be jammed tight into the rifling leade on many rifles.
rc
Ray,
There's a glossary in the following SAAMI document that'll help you "learn the language" of ammo and reloading:
http://saami.org/specifications_and_information/index.cfm?page=glossary
Click on "H" then scroll down to "Head space" and check it out. Bo back to other first letters for stuff you are curious about then check it out.
While that's the standard, everyone does not comply with it. One most common is the term "head space" that's often confused with "head clearance."
Head space was originally based on the dimension from the breech fact to the chamber flat rimmed cartridges stopped at; the .45-70 cartridge, for example.
Nowadays, "head space" is also used by reloaders as the dimension from a case head to the reference diameter on a bottleneck case shoulder. That can be measured before firing and after full length sizing the case to see how much that dimension changed. .002 inch less than the fired dimension is typically right for that of the sized case.
There's a glossary in the following SAAMI document that'll help you "learn the language" of ammo and reloading:
http://saami.org/specifications_and_information/index.cfm?page=glossary
Click on "H" then scroll down to "Head space" and check it out. Bo back to other first letters for stuff you are curious about then check it out.
While that's the standard, everyone does not comply with it. One most common is the term "head space" that's often confused with "head clearance."
Head space was originally based on the dimension from the breech fact to the chamber flat rimmed cartridges stopped at; the .45-70 cartridge, for example.
Nowadays, "head space" is also used by reloaders as the dimension from a case head to the reference diameter on a bottleneck case shoulder. That can be measured before firing and after full length sizing the case to see how much that dimension changed. .002 inch less than the fired dimension is typically right for that of the sized case.
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