Brass Length Tolerance

Caboclo · November 30, 2009, 02:04 AM

Regarding straight-wall pistol cases, I've read in several places that consistent case length is critical to getting a consistent taper. How consistent are we talking here? 0.001"? 0.010"? I'm willing to take the time to do it right, but don't want to waste time unnecessarily.

drail · November 30, 2009, 08:27 AM

Consistent case length would be nice but it's not going to happen unless you trim all of your cases back to the length of the shortest one. It doesn't matter that much on a straight case. Crimping is not as important as having sufficient case neck tension on the bullet. Neck tension does a far better job at holding the bullet in place than crimping the case. You should measure your bullet's dia. and then measure the expander plug inside your flare die. The expander plug needs to be at least 3 or 4 thous. in. smaller than the bullet diameter so that when you seat a bullet without crimping you can hold the round in your hand and push it on the edge of your bench HARD and have no movement of the bullet into the case. If your rounds pass this test the amount of crimp applied can be fairly light and you won't have setback or pull. By using a minimum amount of flaring and crimping your cases will last much longer than they will if you use a heavy crimp to prevent movement. Trying to stop bullet movement with a heavy crimp won't work and will cause other problems. Seating and crimping should be done in two seperate steps. Check out Lyman's M-step expander dies, they flare the case precisely and put less stress on the mouth. I have used them on .357 and .41/.44 Mag. cases that are twenty years old and have never had one split. Never had a bullet pull with heavy recoil/heavy bullet loads. This was how Elmer Keith constructed his heavy loads. He was a pretty clever old guy.

tom234 · November 30, 2009, 03:35 PM

My experience has been straight wall pistol cases don't stretch and over time they actually shrink. Unlike bottle neck rifle cases I don't even bother measuring case length and just shoot them until the case cracks or the case is lost.

Smokey Joe · December 1, 2009, 01:33 PM

Caboclo--You said

Quote:

I've read in several places that consistent case length is critical to getting a consistent taper.

I think what you mean is a consistent crimp on the bullet, not consistent taper. If you're reloading for target shooting, and you're pretty good at it, a consistent crimp will help your accuracy.

If you're loading for just plinking, etc, then the case length in pistols, especially revolvers, is kind of unimportant.

For my target loads, in .357 Mag cases, loaded to .38 Spl levels, I trim the cases to 1.280-1.285". And that's probably fussier than I need to be. No deburring nor chamferring for straight-wall pistol cases, BTW--The bell-mouthing takes care of the chamferring and the crimping removes any bur that might exist.

NWPilgrim · December 1, 2009, 02:12 PM

A taper crimp is less fussy about case length than a roll crimp. Also, the short, straight walled pistol cases hardly stretch compared to the rifle cases. In my experience the case mouths will crack from work hardening before they lengthen significantly. So I try to limit case mouth belling and crimping to the bare minimum.

Given all this, I never trim my pistol cases. I taper crimp only enough to take out the belling of the case mouth. About .001" less than the listed case mouth diameter in the case dimensional drawings. I run a few dummy rounds through the loading sequence (minus the primer and powder) to ensure the final dimensions are good for all of them. I've never found the taper crimp to work for some cases and not for others in a mixed batch. One setting works fine for all my cases.

Caboclo · December 1, 2009, 04:25 PM

Cool, thanks for the info.

qcpunk · December 1, 2009, 07:33 PM

Quote:

My experience has been straight wall pistol cases don't stretch and over time they actually shrink. Unlike bottle neck rifle cases I don't even bother measuring case length and just shoot them until the case cracks or the case is lost.

That would make sense to me. I only reload straight walled pistol rounds right now, so I can't speak about necked cases (but this thread is about straight walled anyways). And I'm not too picky about case length.

So in theory, casings expand and change dimension when fired (we know that), if you expand a straight walled case, the material has to come from somewhere. Yes brass has a certain amount of elasticity and most of the material comes from the wall thickness, but I could see where that expansion could shorten the over all case length a little (like .0001). Does that make sense? Thoughts? Opinions?

drail · December 1, 2009, 10:30 PM

It's true, they do get shorter! Just make sure you remove the flaring and don't worry about it too much. Taper crimps are good.

qcpunk · December 2, 2009, 10:54 PM

Schweet!!! thanks guys

Hook686 · December 3, 2009, 12:39 AM

All that specific advice and no one asked what caliber you were loading. In .30 Carbine (Ruger Blackhawk) I get a lot of case expansion. The round spaces off the neck. The gun really jams if the case length is a bit too much. It seems I trim just about after every other useage. I've not noted the same case stretching with 9mm, .357 magnum, or .44 magnum.

November 30, 2009, 02:04 AM	#1
Caboclo Senior Member Join Date: November 2, 2009 Posts: 212	Brass Length Tolerance Regarding straight-wall pistol cases, I've read in several places that consistent case length is critical to getting a consistent taper. How consistent are we talking here? 0.001"? 0.010"? I'm willing to take the time to do it right, but don't want to waste time unnecessarily.

December 1, 2009, 02:12 PM	#5
NWPilgrim Senior Member Join Date: September 29, 2008 Location: Oregon Posts: 2,346	A taper crimp is less fussy about case length than a roll crimp. Also, the short, straight walled pistol cases hardly stretch compared to the rifle cases. In my experience the case mouths will crack from work hardening before they lengthen significantly. So I try to limit case mouth belling and crimping to the bare minimum. Given all this, I never trim my pistol cases. I taper crimp only enough to take out the belling of the case mouth. About .001" less than the listed case mouth diameter in the case dimensional drawings. I run a few dummy rounds through the loading sequence (minus the primer and powder) to ensure the final dimensions are good for all of them. I've never found the taper crimp to work for some cases and not for others in a mixed batch. One setting works fine for all my cases. __________________ "The ultimate authority ... resides in the people alone. ... The advantage of being armed, which the Americans possess over the people of almost every other nation ... forms a barrier against the enterprises of ambition." - James Madison

December 3, 2009, 12:39 AM	#10
Hook686 Senior Member Join Date: May 22, 2005 Location: USA The Great State of California Posts: 2,090	All that specific advice and no one asked what caliber you were loading. In .30 Carbine (Ruger Blackhawk) I get a lot of case expansion. The round spaces off the neck. The gun really jams if the case length is a bit too much. It seems I trim just about after every other useage. I've not noted the same case stretching with 9mm, .357 magnum, or .44 magnum. __________________ Hook686 When the number of people in institutions reaches 51%, we change sides.

November 30, 2009, 08:27 AM	#2
drail Junior member Join Date: February 2, 2008 Posts: 3,150	Consistent case length would be nice but it's not going to happen unless you trim all of your cases back to the length of the shortest one. It doesn't matter that much on a straight case. Crimping is not as important as having sufficient case neck tension on the bullet. Neck tension does a far better job at holding the bullet in place than crimping the case. You should measure your bullet's dia. and then measure the expander plug inside your flare die. The expander plug needs to be at least 3 or 4 thous. in. smaller than the bullet diameter so that when you seat a bullet without crimping you can hold the round in your hand and push it on the edge of your bench HARD and have no movement of the bullet into the case. If your rounds pass this test the amount of crimp applied can be fairly light and you won't have setback or pull. By using a minimum amount of flaring and crimping your cases will last much longer than they will if you use a heavy crimp to prevent movement. Trying to stop bullet movement with a heavy crimp won't work and will cause other problems. Seating and crimping should be done in two seperate steps. Check out Lyman's M-step expander dies, they flare the case precisely and put less stress on the mouth. I have used them on .357 and .41/.44 Mag. cases that are twenty years old and have never had one split. Never had a bullet pull with heavy recoil/heavy bullet loads. This was how Elmer Keith constructed his heavy loads. He was a pretty clever old guy.

November 30, 2009, 03:35 PM	#3
tom234 Senior Member Join Date: February 14, 2008 Location: Kansas Posts: 753	My experience has been straight wall pistol cases don't stretch and over time they actually shrink. Unlike bottle neck rifle cases I don't even bother measuring case length and just shoot them until the case cracks or the case is lost.

December 1, 2009, 04:25 PM	#6
Caboclo Senior Member Join Date: November 2, 2009 Posts: 212	Cool, thanks for the info.

December 1, 2009, 10:30 PM	#8
drail Junior member Join Date: February 2, 2008 Posts: 3,150	It's true, they do get shorter! Just make sure you remove the flaring and don't worry about it too much. Taper crimps are good.

December 2, 2009, 10:54 PM	#9
qcpunk Senior Member Join Date: October 14, 2009 Location: Farmsville, AZ Posts: 305	Schweet!!! thanks guys