Short cases and pressure

Roland Thunder · September 7, 2011, 12:16 PM

I have some brass cases that are a little under the trim to length of 898 specified by SAAMI. Several that I measured are about .885 or close to it.

Will them being this far shorter than SAMMI cause pressure concerns when the bullet is seated. How far less than the SAMMI OAL can it be before there are pressure concerns

243winxb · September 7, 2011, 12:33 PM

SAAMI lists 45acp brass miminum @ .888" The also list min. & max COL. If you stay within the boundries, plus use a starting load and work up, there should be no pressure problems. http://www.saami.org/PubResources/CC...0Automatic.pdf

Roland Thunder · September 7, 2011, 01:22 PM

Assuming SAAMI COL Min-Max of 1.19 to 1.25 is based on the Min-Max for the brass of .888 to .898 then if my brass is less than .888 (which it is) then overall length of my cartridge will be less than the SAAMI minimum COL

Don H · September 7, 2011, 02:11 PM

Greg,

OAL is determined by the relationship between the ram at top of stroke and the sizing seating/crimp die. No matter what the length of your cases may be, the OAL will remain approximately the same (allowing for normal seating variations). If you were to grind 1/10" off a case and insert it in your reloading process, the OAL of that round would be the same as the other normal cases in that batch...unless you specifically adjust your seating/crimp die for that one round. The base of the bullet will be the same distance from the base of the case as any other round; pressure might be a tad less due to lesser case/bullet contact.

Roland Thunder · September 7, 2011, 02:29 PM

Quote:

Originally Posted by Don P

OAL is determined by the relationship between the ram at top of stroke and the sizing seating/crimp die

That explains it pretty well....thanks

**Unclenick** · September 7, 2011, 03:45 PM

Sometimes a picture is helpful.

wncchester · September 7, 2011, 04:20 PM

If you seat to the same OAL it won't matter a bit what the case lenght is.

September 7, 2011, 12:16 PM	#1
Roland Thunder Senior Member Join Date: December 29, 2010 Location: Gwinnett County Georgia Posts: 1,137	Short cases and pressure I have some brass cases that are a little under the trim to length of 898 specified by SAAMI. Several that I measured are about .885 or close to it. Will them being this far shorter than SAMMI cause pressure concerns when the bullet is seated. How far less than the SAMMI OAL can it be before there are pressure concerns __________________ Do not follow where the path may lead, go, instead where there is no path and leave a trail - Ralph Waldo Emerson

September 7, 2011, 12:33 PM	#2
243winxb Senior Member Join Date: July 26, 2011 Location: USA Posts: 1,758	45 acp Trim Lenght/COL & Pressure SAAMI lists 45acp brass miminum @ .888" The also list min. & max COL. If you stay within the boundries, plus use a starting load and work up, there should be no pressure problems. http://www.saami.org/PubResources/CC...0Automatic.pdf

September 7, 2011, 01:22 PM	#3
Roland Thunder Senior Member Join Date: December 29, 2010 Location: Gwinnett County Georgia Posts: 1,137	Assuming SAAMI COL Min-Max of 1.19 to 1.25 is based on the Min-Max for the brass of .888 to .898 then if my brass is less than .888 (which it is) then overall length of my cartridge will be less than the SAAMI minimum COL __________________ Do not follow where the path may lead, go, instead where there is no path and leave a trail - Ralph Waldo Emerson

September 7, 2011, 03:45 PM	#6
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,738	Sometimes a picture is helpful. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

September 7, 2011, 02:11 PM	#4
Don H Senior Member Join Date: May 9, 2000 Location: SLC,Utah Posts: 2,704	Greg, OAL is determined by the relationship between the ram at top of stroke and the sizing seating/crimp die. No matter what the length of your cases may be, the OAL will remain approximately the same (allowing for normal seating variations). If you were to grind 1/10" off a case and insert it in your reloading process, the OAL of that round would be the same as the other normal cases in that batch...unless you specifically adjust your seating/crimp die for that one round. The base of the bullet will be the same distance from the base of the case as any other round; pressure might be a tad less due to lesser case/bullet contact.

September 7, 2011, 04:20 PM	#7
wncchester Senior Member Join Date: December 1, 2002 Posts: 2,832	If you seat to the same OAL it won't matter a bit what the case lenght is.