Understanding SAAMI - OAL-and punk test

[John Hill]

First, to better understand SAAMI, I have a question on 45 ACP max and min case length. The SAAMI specs show a max case length of .898-.010". Does that mean that a case should not exceed .898" and not be less than .888"?

SAAMI only shows dimensions of a round nose and no other shape. The SAAMI max OAL for 45 ACP is 1.275" and the min is 1.190". That seems straight forward however both of the latest Lyman books show two 200 grain LSWC, one with a OAL of 1.235" which is within the SAAMI specs and a second 200 gr. LSWC with an OAL of 1.161" which is shorter than the SAAMI spec. They also show a 185 gr. LSWC with an OAL of 1.180". How can that be?

Is the idea of a plunk test to have an OAL as long as possible without being longer than 1.275" in 45 ACP and still be able to drop a round in the barrel and have it drop flush with lip and also still cycle through the magazine and through the chamber?
Any help is appreciated.
John

[leadman]

You are correct on the case length. I have not measured the maximum OAL that will fit in a 45 acp magazine but this is something to make sure you do not exceed. Different bullets/boolits have different weight and lengths along with different ogives. All of this will affect the OAL of the loaded cartridge.
You should seat the bullet/boolit so the lube groove of a boolit is covered and the mouth of the case is still on the bearing surface of the boolit/bullet. If the case is unsupported at the mouth it is possible for the case to go past the end of the chamber where it is supposed to headspace on. This can cause misfires at the minimum and excessive pressure and/or gun destruction and personal injury at the maximum.
Your grasp of the plunk test is valid.

[TomAM]

Yes on case length.

The 45 was designed as a round nose, and SAAMI shows it that way. They cannot list every optimal OAL for every conceivable bullet shape. That must be determined by the user. The SAAMI spec pistol is designed to accept a cartridge as described there.

Plunk test is to make sure your ammo will chamber freely. There are many more factors than OAL, such as case diametric measurements, and degree of extension of the bullet's full diameter front band from the case mouth.

[mdi]

SAAMI deminsions are for industry standards. Purely voluntary for the manufacturers. A cartridge assembled to SAAMI dimensions should chamber in any modern production firearm. A cartridge exceeding SAAMI standards may or may not feed, chamber and fire.

I don't think the plunk test is for "longest possible cartridges" but a quick check to determine if one's reloads chamber freely (an over crimped round might not chamber because of a bulged case). I find an OAL from a manual for a particular bullet and start there. There are other dimensions that will hinder passing the plunk test other than OAL, such as case diameter and mouth flare...

[jcren]

Often with lead bullets, optimal accuracy is found with the bullet very close to or touching the rifling lead. The plunk test will help you find that point for that gun. However, my most accurate 200swc load for my 1911 is a little longer than saami and won't chamber in a friend's gun of the same make. Plunk and custom length for max accuracy, Saami for universal compatibility.

[country gent]

Sami drawings use standard blue print dimensioning so .898 +0000 / -.010 is actually .888 - .898 in true measurments. Overal length with any bullet form can be misleading to a point. As its where the dia of the bullet and dia of the leaded meet. A beeter measurement might be similar to headspace. XXX bullet dia ( a point on the bullet at a certain dia) length in relation to standard leade angle. A bore riding round nose can be loaded longer and still chamber than a true round nose can be. A simple gage could be made with the datum dia and 1" long so that any rounds OAL could be measured subtract 1" and you know much closer wether it is close.

[Mk42gunner]

Or said another way-- SAAMI specs are theoretical, plunk test is reality.

Robert

[runfiverun]

cool I didn't know saami come out to your house and measured your guns for you and drew up measurements so stuff from LEE and lyman fit them.

I been doing it all wrong and measuring stuff for myself all these years.
what a GYP!!