Minimum COL

chasep255 · February 3, 2011, 10:27 PM

I know there is a max COL but is there a minimum? For instance, with .40 S&W the max COL is 28.83mm. Is it safe to say have cartridges which measure 28.55mm?

okiefarmer · February 3, 2011, 10:40 PM

I doubt that you ever have to worry about COL on a pistol case. I have never in 35 years of reloading pistol rounds had to trim one, nor have I had to add to any( kinda hard anyway) to reach the COL. What you need to be concerned with more than COL is OAL of loaded round. Because of typical compressed powder loadings in most small capacity cases like 9mm, 40 S&W, 45 ACP et al, there is a MIMIMUM OAL for loaded rounds, there is no maximum OAL. And I didn't spell that wrong, MIMIMUM is the spelling on every page of my Lee Modern Reloading manual, go figger. You can load it out as far as you want until it don't chamber, longer OALs will not increase pressures, shorter OALs will.

Edited to add: It isn't gonna hurt to have a COL of 28.55mm, this is only 1/100th of an inch shorter than 28.83 mm, and even headspacing on the casemouth on a pistol round will not be affected in this case. The extracators on many pistols do more headspacing than I expect many realize.

farmerboy · February 3, 2011, 10:57 PM

I would'nt necessarly say there is never a need to have to trim a pistol case. If you wont them to have the same amount of crimp on each and every one of them, sure you do. setting up your crimp on the longest one and then say you have alot of them say .045 shorter, do you think you will have the same crimp?

chasep255 · February 3, 2011, 11:00 PM

So I just need to make sure that my loads are over the min length. Also do I need to crimp my reloads?

farmerboy · February 4, 2011, 12:15 AM

it doesnt mean that either. If you just wont them to go bang and they are just being sent down range at paper or coke cans, you make them just like you want and have a blast. What caliber are these ? what weapon and what are they for and what kind of bullets would also be more helpful..

chasep255 · February 4, 2011, 02:30 PM

40 S&W 200 gr Bullets with Power Pistol powder

Shoney · February 4, 2011, 04:35 PM

okiefarmer
the abbreviations OAL and COL mean the same thing. OAL is Over All Length of the cartridge, while COL is Cartridge Overall Length. The different terms have the same meaning.

Case length is expressed by Trim Length and Maximum Case Length. Straight walled pistol cases do not increase in length, in fact they shorten minutely with each sizing.

chasepreuninger
The maximum case length is usually limited to what will fit/function from the magazine. Rarely is there a problem with a short chamber limiting OAL/COL. I have never heard of that problem in real life.

The min/max OAL/COL are not written in stone. You can vary them a bit, according to the need; i.e. the weapon will not chamber a round unless it is 0.020" under the recipe's OAL/COL. Here is where you must understand that shortening the OAL will increase pressure. The generally accepted thing to do, when shortening the AOL, is reduce the staring load 15-20% under max and work up, watching for pressure signs. (There are few such signs with pistols, but this is another thread in itself.)

CRIMPING is done by properly sizing the case. Then after the bullet is seated to the proper depth, you just remove the bell' and that will give you the proper crimp.

Many novice reloaders think they must apply more crimp than just removing the bell from the case, but that will cause the bullet to be loose in the case by slightly bulging out the brass. That loose brass may allow the bullet to set back into the case (causing an over pressure situation when fired), while in the magazine, while the weapon is fired. The "neck tension" provided by the sizing is sufficient to hold the bullet in place without applying an over-crimp.

Good Shooting!

700cdl · February 4, 2011, 04:59 PM

Most of the above is pretty accurate, but I want to touch on a couple of things. Max COL isn't usually a problem unless you start touching the lands. It's going to cause pressures to rise, just as seating too deeply will. And with regard to crimp, if your working with an auto loading handgun or rifle cartridge crimp is usually insignificant. However, a revolver, especially magnums produce a lot of pressure that blows back into other chambered rounds in the cylinder, and will, as I've experienced first hand, dislodge the bullets usually causing them to jump up, rather than setting them back. It's some what more pronounced with bullets that have a shorter olgive which increases the distance to the bearing surface. This seems to contribute to the problem. I've loaded 158 gr. JHPs and 110 JHP of the same design and brand, producing like pressures and the 110s were very difficult to keep in the case and required a very tight crimp, in fact a taper crimp isn't really recomended, a role crimp is the easy way to avoid this problem.

Shoney · February 4, 2011, 05:17 PM

700cdl comments are very good and valid for wheel guns. My post above is aimed at the 40S&W, which this thread is about. My comments also apply to all straight walled semi-auto pistol reloading, as I didn't clarify that in the above post to chasepreuninger.

**Unclenick** · February 4, 2011, 05:26 PM

Chasepreuninger,

The SAAMI maximum COL is only there to insure your cartridges aren't too long to fit in a SAAMI compliant magazine. The spec allows gun makers to design their magazines to accept that length. Maximum case length is to ensure you don't get excess pressure, as can happen in a rifle or a revolver chamber, but in a case that headspaces on the mouth, like the .40 S&W, even that isn't really an issue as long as you don't crimp them below minimum case mouth diameter and they aren't so long that if you drop a resized (but not yet expanded or flared) case into your pistol's chamber, the head doesn't stick out above even with the end of the barrel.

Much unevenness in case length is to be avoided because uneven length cases will crimp to different mouth diameters and with different firmness. They should probably be within 0.005" of each other for best performance. That's about as close as the manufacturers seem to keep them.

As to a minimum, there is no such thing because bullet designs are so different. However, sating too deeply raises the danger of excess pressure, particularly in a short, high pressure round like the .40 S&W. That is because seating deeper robs the powder of some of its burning space. That can raise pressures dramatically. For that reason, even if two bullets have the same weight, if they have different lengths they will not use the same COL with the same load. Or, stated another way, if two bullets are the same length, but smooth feeding requires you to use different COL's, then the powder charges need to be different to create the same pressure.

In general, same-weight bullets that have the same construction (e.g., both jacketed or both cast) can use the same powder charge if their seating depth is the same. NOTE: seating depth is NOT COL. Seating depth is how far the bullet base sticks down into the case. The idea is to match up the powder space underneath, so even seating depth isn't the perfect measure if your cases are different lengths. The ideal measure would be how far the base of the bullet is from head of the case, and that can be done by always using the SAAMI maximum case length to calculate seating depth. If your actual case is shorter, the mouth is just lower down on the bullet, but the distance from the head to the bullet base will be the same.

Seating Depth = Bullet Length + SAAMI Case Length - COL

So, if I look up a manual load for a bullet that is 0.560 long that is given a COL of 1.075", and I have another bullet the same weight that is 0.600 long that I want to use the same charge with, how do I adjust it? The SAAMI maximum case length is 0.850", so:

Find seating depth of original load with above formula:

Seating Depth = 0.540" + 0.850" - 1.075" = 0.315"

To find the COL to use with the longer bullet, you just rearrange the formula to find COL:

New Bullet COL = Bullet Length + SAAMI Case Length - Seating Depth

New Bullet COL = 0.600 + 0.850" - 0.315 = 1.135"

If you get a result that is over SAAMI maximum or that, because of the nose shape, won't feed reliably, then you know you'll have to seat deeper and reduce the powder charge for that bullet.

okiefarmer · February 4, 2011, 05:35 PM

Shoney,
I'm aware that they mean the same thing. I erred in assuming the OP was referring to the empty case length in his opening question. My bad. And I don't have a reference to MAX lengths of anything in idividual loadings. The dimensions of the cartridge at the beginnings of each caliber's section ( in Lee's book) is the only reference to what would be asumed as MAX, and what will fit in most magazines without hammering them in. What I didn't do a very good job of 'splainin' was the importance of not loading to any less than minimum OAL in compressed loads. That would be bad.

I thought he was asking about the brass length, and not the cartridge length, and as several agreed to, pistol brass does not grow, it normally shrinks. I should read the fine print next time.

wncchester · February 4, 2011, 06:40 PM

duplicate

wncchester · February 4, 2011, 06:44 PM

"...a revolver, especially magnums produce a lot of pressure that blows back into other chambered rounds in the cylinder, and will, as I've experienced first hand, dislodge the bullets usually causing them to jump up, rather than setting them back."

Say what? That's unique! External pressure applied to an exposed bullet in a cylinder will force the bullet to move "up", FORWARD, and towards the high pressure?

Would you believe, perhaps, recoil is what's pulling your magnum revolver bullets forward?

Small cases for high intensity cartridges tend to be chambered in autoloaders, think 9mm and .40. They are far more sensitive to deeper seating than larger, lower pressure cartridges because small seating changes can easily greatly reduce the combusion chamber volume by a significant percentage.

**Unclenick** · February 7, 2011, 11:32 AM

When recoil slams the cylinder back against the case rim, pulling the case rearward, bullet inertia causes the case to have to pull pretty hard to get the bullet to back up with it that suddenly. Under heavy recoil or low bullet grip tension (poor crimp, inadequate sizing, etc.), the case just can't hang on hard enough to accomplish that, so the bullet winds up backed out of the case. In effect, a revolver is an inertial bullet puller that you hope doesn't work.

wncchester · February 7, 2011, 04:49 PM

"In effect, a revolver is an inertial bullet puller ..."

"Ezactly. Any pulled bullets sure aren't due to external high pressure forcing them OUT!

February 3, 2011, 10:27 PM	#1
chasep255 Senior Member Join Date: December 21, 2009 Location: NJ Posts: 727	Minimum COL I know there is a max COL but is there a minimum? For instance, with .40 S&W the max COL is 28.83mm. Is it safe to say have cartridges which measure 28.55mm?

February 4, 2011, 04:35 PM	#7
Shoney Senior Member Join Date: February 21, 2002 Location: Transplanted from Montana Posts: 2,311	okiefarmer the abbreviations OAL and COL mean the same thing. OAL is Over All Length of the cartridge, while COL is Cartridge Overall Length. The different terms have the same meaning. Case length is expressed by Trim Length and Maximum Case Length. Straight walled pistol cases do not increase in length, in fact they shorten minutely with each sizing. chasepreuninger The maximum case length is usually limited to what will fit/function from the magazine. Rarely is there a problem with a short chamber limiting OAL/COL. I have never heard of that problem in real life. The min/max OAL/COL are not written in stone. You can vary them a bit, according to the need; i.e. the weapon will not chamber a round unless it is 0.020" under the recipe's OAL/COL. Here is where you must understand that shortening the OAL will increase pressure. The generally accepted thing to do, when shortening the AOL, is reduce the staring load 15-20% under max and work up, watching for pressure signs. (There are few such signs with pistols, but this is another thread in itself.) CRIMPING is done by properly sizing the case. Then after the bullet is seated to the proper depth, you just remove the bell' and that will give you the proper crimp. Many novice reloaders think they must apply more crimp than just removing the bell from the case, but that will cause the bullet to be loose in the case by slightly bulging out the brass. That loose brass may allow the bullet to set back into the case (causing an over pressure situation when fired), while in the magazine, while the weapon is fired. The "neck tension" provided by the sizing is sufficient to hold the bullet in place without applying an over-crimp. Good Shooting! __________________ I pledge allegiance to the Flag - - -, and to the Republic for which it stands….Our Forefathers were brilliant for giving us a Republic, not a democracy! Do you know the difference??? and WHY?http://www.wallbuilders.com/LIBissue...les.asp?id=111

February 4, 2011, 05:17 PM	#9
Shoney Senior Member Join Date: February 21, 2002 Location: Transplanted from Montana Posts: 2,311	700cdl comments are very good and valid for wheel guns. My post above is aimed at the 40S&W, which this thread is about. My comments also apply to all straight walled semi-auto pistol reloading, as I didn't clarify that in the above post to chasepreuninger. __________________ I pledge allegiance to the Flag - - -, and to the Republic for which it stands….Our Forefathers were brilliant for giving us a Republic, not a democracy! Do you know the difference??? and WHY?http://www.wallbuilders.com/LIBissue...les.asp?id=111

February 4, 2011, 05:26 PM	#10
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Chasepreuninger, The SAAMI maximum COL is only there to insure your cartridges aren't too long to fit in a SAAMI compliant magazine. The spec allows gun makers to design their magazines to accept that length. Maximum case length is to ensure you don't get excess pressure, as can happen in a rifle or a revolver chamber, but in a case that headspaces on the mouth, like the .40 S&W, even that isn't really an issue as long as you don't crimp them below minimum case mouth diameter and they aren't so long that if you drop a resized (but not yet expanded or flared) case into your pistol's chamber, the head doesn't stick out above even with the end of the barrel. Much unevenness in case length is to be avoided because uneven length cases will crimp to different mouth diameters and with different firmness. They should probably be within 0.005" of each other for best performance. That's about as close as the manufacturers seem to keep them. As to a minimum, there is no such thing because bullet designs are so different. However, sating too deeply raises the danger of excess pressure, particularly in a short, high pressure round like the .40 S&W. That is because seating deeper robs the powder of some of its burning space. That can raise pressures dramatically. For that reason, even if two bullets have the same weight, if they have different lengths they will not use the same COL with the same load. Or, stated another way, if two bullets are the same length, but smooth feeding requires you to use different COL's, then the powder charges need to be different to create the same pressure. In general, same-weight bullets that have the same construction (e.g., both jacketed or both cast) can use the same powder charge if their seating depth is the same. NOTE: seating depth is NOT COL. Seating depth is how far the bullet base sticks down into the case. The idea is to match up the powder space underneath, so even seating depth isn't the perfect measure if your cases are different lengths. The ideal measure would be how far the base of the bullet is from head of the case, and that can be done by always using the SAAMI maximum case length to calculate seating depth. If your actual case is shorter, the mouth is just lower down on the bullet, but the distance from the head to the bullet base will be the same. Seating Depth = Bullet Length + SAAMI Case Length - COL So, if I look up a manual load for a bullet that is 0.560 long that is given a COL of 1.075", and I have another bullet the same weight that is 0.600 long that I want to use the same charge with, how do I adjust it? The SAAMI maximum case length is 0.850", so: Find seating depth of original load with above formula: Seating Depth = 0.540" + 0.850" - 1.075" = 0.315" To find the COL to use with the longer bullet, you just rearrange the formula to find COL: New Bullet COL = Bullet Length + SAAMI Case Length - Seating Depth New Bullet COL = 0.600 + 0.850" - 0.315 = 1.135" If you get a result that is over SAAMI maximum or that, because of the nose shape, won't feed reliably, then you know you'll have to seat deeper and reduce the powder charge for that bullet. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle Last edited by Unclenick; February 4, 2011 at 05:35 PM.

February 4, 2011, 06:40 PM	#12
wncchester Senior Member Join Date: December 1, 2002 Posts: 2,832	duplicate Last edited by wncchester; February 4, 2011 at 10:23 PM.

February 3, 2011, 10:40 PM	#2
okiefarmer Senior Member Join Date: February 20, 2006 Location: Oklahoma Posts: 381	I doubt that you ever have to worry about COL on a pistol case. I have never in 35 years of reloading pistol rounds had to trim one, nor have I had to add to any( kinda hard anyway) to reach the COL. What you need to be concerned with more than COL is OAL of loaded round. Because of typical compressed powder loadings in most small capacity cases like 9mm, 40 S&W, 45 ACP et al, there is a MIMIMUM OAL for loaded rounds, there is no maximum OAL. And I didn't spell that wrong, MIMIMUM is the spelling on every page of my Lee Modern Reloading manual, go figger. You can load it out as far as you want until it don't chamber, longer OALs will not increase pressures, shorter OALs will. Edited to add: It isn't gonna hurt to have a COL of 28.55mm, this is only 1/100th of an inch shorter than 28.83 mm, and even headspacing on the casemouth on a pistol round will not be affected in this case. The extracators on many pistols do more headspacing than I expect many realize.

February 3, 2011, 10:57 PM	#3
farmerboy Junior member Join Date: May 16, 2009 Location: Central Texas Posts: 1,343	I would'nt necessarly say there is never a need to have to trim a pistol case. If you wont them to have the same amount of crimp on each and every one of them, sure you do. setting up your crimp on the longest one and then say you have alot of them say .045 shorter, do you think you will have the same crimp?

February 3, 2011, 11:00 PM	#4
chasep255 Senior Member Join Date: December 21, 2009 Location: NJ Posts: 727	So I just need to make sure that my loads are over the min length. Also do I need to crimp my reloads?

February 4, 2011, 12:15 AM	#5
farmerboy Junior member Join Date: May 16, 2009 Location: Central Texas Posts: 1,343	it doesnt mean that either. If you just wont them to go bang and they are just being sent down range at paper or coke cans, you make them just like you want and have a blast. What caliber are these ? what weapon and what are they for and what kind of bullets would also be more helpful..

February 4, 2011, 02:30 PM	#6
chasep255 Senior Member Join Date: December 21, 2009 Location: NJ Posts: 727	40 S&W 200 gr Bullets with Power Pistol powder

February 4, 2011, 04:59 PM	#8
700cdl Senior Member Join Date: December 6, 2010 Posts: 216	Most of the above is pretty accurate, but I want to touch on a couple of things. Max COL isn't usually a problem unless you start touching the lands. It's going to cause pressures to rise, just as seating too deeply will. And with regard to crimp, if your working with an auto loading handgun or rifle cartridge crimp is usually insignificant. However, a revolver, especially magnums produce a lot of pressure that blows back into other chambered rounds in the cylinder, and will, as I've experienced first hand, dislodge the bullets usually causing them to jump up, rather than setting them back. It's some what more pronounced with bullets that have a shorter olgive which increases the distance to the bearing surface. This seems to contribute to the problem. I've loaded 158 gr. JHPs and 110 JHP of the same design and brand, producing like pressures and the 110s were very difficult to keep in the case and required a very tight crimp, in fact a taper crimp isn't really recomended, a role crimp is the easy way to avoid this problem.

February 4, 2011, 05:35 PM	#11
okiefarmer Senior Member Join Date: February 20, 2006 Location: Oklahoma Posts: 381	Shoney, I'm aware that they mean the same thing. I erred in assuming the OP was referring to the empty case length in his opening question. My bad. And I don't have a reference to MAX lengths of anything in idividual loadings. The dimensions of the cartridge at the beginnings of each caliber's section ( in Lee's book) is the only reference to what would be asumed as MAX, and what will fit in most magazines without hammering them in. What I didn't do a very good job of 'splainin' was the importance of not loading to any less than minimum OAL in compressed loads. That would be bad. I thought he was asking about the brass length, and not the cartridge length, and as several agreed to, pistol brass does not grow, it normally shrinks. I should read the fine print next time.

February 4, 2011, 06:44 PM	#13
wncchester Senior Member Join Date: December 1, 2002 Posts: 2,832	"...a revolver, especially magnums produce a lot of pressure that blows back into other chambered rounds in the cylinder, and will, as I've experienced first hand, dislodge the bullets usually causing them to jump up, rather than setting them back." Say what? That's unique! External pressure applied to an exposed bullet in a cylinder will force the bullet to move "up", FORWARD, and towards the high pressure? Would you believe, perhaps, recoil is what's pulling your magnum revolver bullets forward? Small cases for high intensity cartridges tend to be chambered in autoloaders, think 9mm and .40. They are far more sensitive to deeper seating than larger, lower pressure cartridges because small seating changes can easily greatly reduce the combusion chamber volume by a significant percentage.

February 7, 2011, 11:32 AM	#14
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	When recoil slams the cylinder back against the case rim, pulling the case rearward, bullet inertia causes the case to have to pull pretty hard to get the bullet to back up with it that suddenly. Under heavy recoil or low bullet grip tension (poor crimp, inadequate sizing, etc.), the case just can't hang on hard enough to accomplish that, so the bullet winds up backed out of the case. In effect, a revolver is an inertial bullet puller that you hope doesn't work. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

February 7, 2011, 04:49 PM	#15
wncchester Senior Member Join Date: December 1, 2002 Posts: 2,832	"In effect, a revolver is an inertial bullet puller ..." "Ezactly. Any pulled bullets sure aren't due to external high pressure forcing them OUT!