Case dimention question

Reich · January 22, 2013, 04:56 PM

I just bought RCBS die set for .222 rem. After trimming and sending the case through the decap size die all dimentions are perfect except neck diameter. All the Materal I read so far says it should be .253, but I keep ending up with .245. Not only is it a pain to seat the bullets,but I am worried about pressure problems. Am I good to run with these cases?

Reich

**Unclenick** · January 22, 2013, 05:42 PM

The drawing is here. Notice that under the name of the cartridge it says:

"UNLESS OTHERWISE NOTED
BODY DIA -.008 (0.20)"

Where it gives the neck as 0.253, there is no tolerance noted. That means that, even though the drawing says 0.253", that's only the maximum, and the -0.008" tolerance means it can be as small as 0.245". Note also that this is the number with the bullet in place and not before you've seated the bullet, which will be smaller.

To make seating easier, be sure to have adequate chamfer on the case or get a Lyman M die for your chambering. It puts a small step in the mouth that lets you seat the bullets upright and start in straight.

Reich · January 22, 2013, 08:41 PM

Thanks for your help

oneoldsap · January 23, 2013, 07:51 AM

Trim after sizing , not before !

FrankenMauser · January 23, 2013, 04:23 PM

Quote:

Trim after sizing , not before !

Some trimmers use pilots that are sized for fired cases. Sized cases won't fit on the pilot. So, you don't have much choice in the matter, with those trimmers.

**Unclenick** · January 24, 2013, 12:01 PM

If you only have the ability to trim before resizing (though buying a different pilot would fix that), then you want to apply your calipers to see how much resizing grows these cases and trim that much further extra short before resizing. This amount will vary with individual chambers, so you have to measure it for the particular gun and brass. Brass from a loose chamber will grow more during resizing than one fired in a tight chamber, all else being equal.

January 22, 2013, 04:56 PM	#1
Reich Junior Member Join Date: February 26, 2012 Posts: 8	Case dimention question I just bought RCBS die set for .222 rem. After trimming and sending the case through the decap size die all dimentions are perfect except neck diameter. All the Materal I read so far says it should be .253, but I keep ending up with .245. Not only is it a pain to seat the bullets,but I am worried about pressure problems. Am I good to run with these cases? Reich

January 22, 2013, 05:42 PM	#2
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,061	The drawing is here. Notice that under the name of the cartridge it says: "UNLESS OTHERWISE NOTED BODY DIA -.008 (0.20)" Where it gives the neck as 0.253, there is no tolerance noted. That means that, even though the drawing says 0.253", that's only the maximum, and the -0.008" tolerance means it can be as small as 0.245". Note also that this is the number with the bullet in place and not before you've seated the bullet, which will be smaller. To make seating easier, be sure to have adequate chamfer on the case or get a Lyman M die for your chambering. It puts a small step in the mouth that lets you seat the bullets upright and start in straight. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

January 22, 2013, 08:41 PM	#3
Reich Junior Member Join Date: February 26, 2012 Posts: 8	Thanks Thanks for your help

January 23, 2013, 07:51 AM	#4
oneoldsap Senior Member Join Date: September 16, 2009 Location: I live in the foot of the Green Mountains of Vermont Posts: 1,602	Trim after sizing , not before ! __________________ Don't forget to have your liberals spayed or neutered !

January 24, 2013, 12:01 PM	#6
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,061	If you only have the ability to trim before resizing (though buying a different pilot would fix that), then you want to apply your calipers to see how much resizing grows these cases and trim that much further extra short before resizing. This amount will vary with individual chambers, so you have to measure it for the particular gun and brass. Brass from a loose chamber will grow more during resizing than one fired in a tight chamber, all else being equal. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle