Minimum pistol brass case length

Guss · December 19, 2010, 09:39 PM

I have recently gotten into reloading. For the moment it's just .380 and 9mm, but in the future may include .45 and 10mm.

In measuring my brass cases, I find considerable variation. I can find information on maximum brass case length online, but I'm having a problem with finding minimums. Where is the danger point? How short before they start misfiring? I haven't had a misfire yet, but I don't want to have it happen either.

Shoney · December 19, 2010, 10:09 PM

Guss

WELCOME TO TFL!!!

You do not need to trim straight walled semi-auto pistol brass. The cartridges just need to be the same length (OAL).

My experience with straight walled semi-auto brass shows that brass gets shorter with each loading. The cartridge is supposed to headspace on the front lip of the case on the front of the chamber. However, in reality, as the case gets shorter, the extractor holds the cartridge against the slide face where the firing pin can do its job.

Worst case scenario with short brass is that it will likely fall into the chamber and not be caught by the extractor, in which case it will not fire. I have 40SW cases that have been loaded 10-12 times and 45 cases that are somewhere over 25 loadings or more. There have been no malfunctions. I put a very light bell on my cases, compared to a lot of other loader, and I think that this reduces shortening. No scientific proof of that though.

Guss · December 19, 2010, 10:56 PM

Since my goals are reliability and repeat consistency, I still view it as a potential problem. There is not only the potential for misfire, but with different case lengths, the volume of the area containing the powder will vary.

Jim Watson · December 19, 2010, 11:13 PM

Case length within the manufacturing tolerances you are worrying about is nothing to worry about unless you are shooting NRA 50 yard slowfire or equal.

If you ARE shooting 50 yard slowfire, buy a batch of brass of the same manufacturing lot number and they will be close enough.

Guss · December 20, 2010, 02:29 AM

That's what I'm getting at - What should the manufacturers' tolerances be?
My Winchesters seem to have quite a range by my measurement.
Fiocchi in 380 seems on the short side.

At the moment, I'm thinking I will use the specifications that Starline gives at their website for their product.

Hornady has given suggested trim lengths and minimum lengths that might also serve as a guide.

Shoney · December 20, 2010, 04:35 AM

Guss

As long as all the cartridges have the same OAL, the internal volume of each round is identical, regardless of the case length. You should be more concerned with having the same powder charge in each cartridge.

Guss · December 20, 2010, 08:34 AM

Shoney - You're right about that, but I'm still wondering what happens with the firing pin if the front case edge doesn't connect with the internal ledge. If the brass is just held by the edge of the extractor, that kind of takes the firmness out of it.

4runnerman · December 20, 2010, 09:10 AM

I have never had a case to short. Usaully they grow in length not shrink. If some one has trimmed them to short i can see a issue other than that how did they get to short?.

PA-Joe · December 20, 2010, 09:19 AM

Most reloading manuals list a cut to length for cases. I would say that is the minium. Have you checked a good reloading manual? Another option is to get a LEE case trimmer and trim all of your brass to that length.

engineermike · December 20, 2010, 10:07 AM

Guss,
I have the same questions as you. (So far no answers yet) I have found that when it comes to loading pistol ammo you start close to the Max col and go down until you find that col that your pistol/rifle likes. I have only seen one place where there is a minimum case length but I forget the page and it cost a fee to get the information. Some feel that case length is a factor in shooting and trim to a specific length (This seems to vary from gun to gun) but if you are going to use a crimp (Taper on most pistol ammo) to take the bell out of your cases (Reloading only) you may need to trim your cases to the same lengths. (I crimp but have yet to trim my cases) I have not trimmed my cases but I have to crimp my 38 special rounds to get them to fit into the cylinder of my revolver. I too have found that the col of manufactured ammo comes in varying lengths and I am talking about rounds in the same box but they seem to shoot ok. (This might be the cause of some cycling problems I read about on this forum. (Or not) Some day I am going to buy a trimmer (Used) and trim a few cases and see what that might do. (If anything) I agree thought, that if this case and bullet is to fit into a place that has specifications/tolerances then there has to be, or should be max's and min's but the min's seem to not be listed everywhere. When reloading maybe that col the gun likes so much is reached before you get to the minimum length but I too would like to know what that length is even if I never use it.

Mike

4runnerman · December 20, 2010, 10:30 AM

That info was very easy to find guys
Min-.744 length
best for accuracy was .750

Hornady is saying any thing shorter than .749 may cause failer to fire. Guys that have done the tests are saying .744 min

jbrown13 · December 20, 2010, 10:35 AM

If someone has the book "The ABC's of Reloading", I seem to remember there being a suggested minimum case length stated in the chapter on trimming. I can't check this out since my son has borrowed my copy and lives 300 miles away. Of course I could be hallucinating, in that my brain is worn out.

sc928porsche · December 20, 2010, 11:35 AM

Why would a case get shorter? Ok......On factory ammo, the case diameter is smaller than the chamber (otherwise you wouldnt be able to insert it into the chamber. When fired, it expands to fit the chamber. Brass will rebound slightly. Your fired case is now larger in diameter than the original. In order for the case to grow in diameter, the material must come from somewhere. The path of least resistance is in the length, so it becomes shorter. When you resize, the case becomes smaller than the chamber diameter again. Depending on the sizing die will determine how much it is reduced and how much it will grow back. Bottleneck cartridges grow because of how they are headspaced.

At least that was the theory that was explained to me many years ago by a few fellas that seemed to know what they were talking about.

Shoney · December 20, 2010, 01:00 PM

Straight wall semi-auto pistol brass gets microscopically shorter with each reloading! I have measured brass in 45ACP, 40SW, 9mmLugar, 9X18, and 380 to find that this is true.

What causes brass to stretch? As the firing pin hits the primer, the cartridge is pushed forward, the powder begins to burn, pressure builds in the case. At this point, if the pressure is great enough, the case expands outward and grips the sidewall of the chamber, the primer backs out until it hits the bolt face, the case from the web to head stretches as the case head backs out to hit the bolt face, and the primer is reseated.
There is an excellent illustration of this in post #6 of this thread:
http://thefiringline.com/forums/showthread.php?t=432628

In cartridges that do not have sufficient pressure generated to grip the sidewall of the chamber:
The firing pin strikes the primer and pushes the cartridge forward, powder burns, pressure builds, the primer backs out, and almost simultaneously, the case moves backward, and both primer and case strikes the bolt face. The case is ejected without any stretch.

zippy13 · December 20, 2010, 02:08 PM

Guss,
If you have an book like the old NRA's Handloading by Wm C Davis, Jr, you'll find the standard dimensions for each cartridge case and chamber in the reference section.

In you situation, the .380ACP has a case length dimension of .680(-.010)" in the reference section. With the reloading data it notes that the maximum case length is .680" (which is consistent with the standard) and a "trim-to" length of .673" (which is longer than the .670" minimum permitted in the standard). If you are looking for consistency, as noted by Jim Watson, then set your case trimmer to .673" and and start trimming. Personally, my PPK/S isn't my go-to gun for 50-yard work.

If your Fiocchi cases measure less than .670" then they're out of spec.
FYI: I just measured some of the cases of the .380ACP's ammo I have. W-W's were in the neighborhood of .675", Fiocchi's around .678", and some commercial reloads were around .687" (well over spec).

Guss · December 20, 2010, 07:18 PM

Zippy - That's the kind of straightforward information I was after.
A person can't be expected to buy a string of expensive books in hopes that one will have the few numbers he is after.
I will return to the library and see what they can bring in.

noylj · December 20, 2010, 08:03 PM

Look for the "trim-to-length" and you can assume that any brass you have that falls below that AFTER resizing is too short.
Personally, I save those cases that are within 0.005" of the maximum case length for when I need the highest accuracy (particularly in 9x19).
The firing pin actually is hit so hard that it travels a good distance and even my shortest cases have never had a problem being fired.
It is good to worry, but if your reloading manuals aren't warning you and the forums aren't warning you, you may be worrying about a non-issue.

December 19, 2010, 09:39 PM	#1
Guss Junior Member Join Date: August 19, 2010 Location: Tampa Posts: 6	Minimum pistol brass case length I have recently gotten into reloading. For the moment it's just .380 and 9mm, but in the future may include .45 and 10mm. In measuring my brass cases, I find considerable variation. I can find information on maximum brass case length online, but I'm having a problem with finding minimums. Where is the danger point? How short before they start misfiring? I haven't had a misfire yet, but I don't want to have it happen either.

December 20, 2010, 10:30 AM	#11
4runnerman Senior Member Join Date: January 16, 2010 Location: Minnesota Posts: 3,577	That info was very easy to find guys Min-.744 length best for accuracy was .750 Hornady is saying any thing shorter than .749 may cause failer to fire. Guys that have done the tests are saying .744 min Last edited by 4runnerman; December 20, 2010 at 10:46 AM.

December 19, 2010, 10:09 PM	#2
Shoney Senior Member Join Date: February 21, 2002 Location: Transplanted from Montana Posts: 2,311	Guss WELCOME TO TFL!!! You do not need to trim straight walled semi-auto pistol brass. The cartridges just need to be the same length (OAL). My experience with straight walled semi-auto brass shows that brass gets shorter with each loading. The cartridge is supposed to headspace on the front lip of the case on the front of the chamber. However, in reality, as the case gets shorter, the extractor holds the cartridge against the slide face where the firing pin can do its job. Worst case scenario with short brass is that it will likely fall into the chamber and not be caught by the extractor, in which case it will not fire. I have 40SW cases that have been loaded 10-12 times and 45 cases that are somewhere over 25 loadings or more. There have been no malfunctions. I put a very light bell on my cases, compared to a lot of other loader, and I think that this reduces shortening. No scientific proof of that though.

December 19, 2010, 10:56 PM	#3
Guss Junior Member Join Date: August 19, 2010 Location: Tampa Posts: 6	Since my goals are reliability and repeat consistency, I still view it as a potential problem. There is not only the potential for misfire, but with different case lengths, the volume of the area containing the powder will vary.

December 19, 2010, 11:13 PM	#4
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 19,163	Case length within the manufacturing tolerances you are worrying about is nothing to worry about unless you are shooting NRA 50 yard slowfire or equal. If you ARE shooting 50 yard slowfire, buy a batch of brass of the same manufacturing lot number and they will be close enough.

December 20, 2010, 02:29 AM	#5
Guss Junior Member Join Date: August 19, 2010 Location: Tampa Posts: 6	That's what I'm getting at - What should the manufacturers' tolerances be? My Winchesters seem to have quite a range by my measurement. Fiocchi in 380 seems on the short side. At the moment, I'm thinking I will use the specifications that Starline gives at their website for their product. Hornady has given suggested trim lengths and minimum lengths that might also serve as a guide.

December 20, 2010, 04:35 AM	#6
Shoney Senior Member Join Date: February 21, 2002 Location: Transplanted from Montana Posts: 2,311	Guss As long as all the cartridges have the same OAL, the internal volume of each round is identical, regardless of the case length. You should be more concerned with having the same powder charge in each cartridge.

December 20, 2010, 08:34 AM	#7
Guss Junior Member Join Date: August 19, 2010 Location: Tampa Posts: 6	Shoney - You're right about that, but I'm still wondering what happens with the firing pin if the front case edge doesn't connect with the internal ledge. If the brass is just held by the edge of the extractor, that kind of takes the firmness out of it.

December 20, 2010, 09:10 AM	#8
4runnerman Senior Member Join Date: January 16, 2010 Location: Minnesota Posts: 3,577	I have never had a case to short. Usaully they grow in length not shrink. If some one has trimmed them to short i can see a issue other than that how did they get to short?.

December 20, 2010, 09:19 AM	#9
PA-Joe Senior Member Join Date: June 9, 2010 Location: NEPA Posts: 909	Most reloading manuals list a cut to length for cases. I would say that is the minium. Have you checked a good reloading manual? Another option is to get a LEE case trimmer and trim all of your brass to that length.

December 20, 2010, 10:07 AM	#10
engineermike Junior member Join Date: March 14, 2010 Location: Oklahaoma City Posts: 538	Guss, I have the same questions as you. (So far no answers yet) I have found that when it comes to loading pistol ammo you start close to the Max col and go down until you find that col that your pistol/rifle likes. I have only seen one place where there is a minimum case length but I forget the page and it cost a fee to get the information. Some feel that case length is a factor in shooting and trim to a specific length (This seems to vary from gun to gun) but if you are going to use a crimp (Taper on most pistol ammo) to take the bell out of your cases (Reloading only) you may need to trim your cases to the same lengths. (I crimp but have yet to trim my cases) I have not trimmed my cases but I have to crimp my 38 special rounds to get them to fit into the cylinder of my revolver. I too have found that the col of manufactured ammo comes in varying lengths and I am talking about rounds in the same box but they seem to shoot ok. (This might be the cause of some cycling problems I read about on this forum. (Or not) Some day I am going to buy a trimmer (Used) and trim a few cases and see what that might do. (If anything) I agree thought, that if this case and bullet is to fit into a place that has specifications/tolerances then there has to be, or should be max's and min's but the min's seem to not be listed everywhere. When reloading maybe that col the gun likes so much is reached before you get to the minimum length but I too would like to know what that length is even if I never use it. Mike

December 20, 2010, 10:35 AM	#12
jbrown13 Senior Member Join Date: December 28, 2009 Location: Perry, GA Posts: 105	If someone has the book "The ABC's of Reloading", I seem to remember there being a suggested minimum case length stated in the chapter on trimming. I can't check this out since my son has borrowed my copy and lives 300 miles away. Of course I could be hallucinating, in that my brain is worn out.

December 20, 2010, 11:35 AM	#13
sc928porsche Senior Member Join Date: May 29, 2008 Location: now living in alabama Posts: 2,433	Why would a case get shorter? Ok......On factory ammo, the case diameter is smaller than the chamber (otherwise you wouldnt be able to insert it into the chamber. When fired, it expands to fit the chamber. Brass will rebound slightly. Your fired case is now larger in diameter than the original. In order for the case to grow in diameter, the material must come from somewhere. The path of least resistance is in the length, so it becomes shorter. When you resize, the case becomes smaller than the chamber diameter again. Depending on the sizing die will determine how much it is reduced and how much it will grow back. Bottleneck cartridges grow because of how they are headspaced. At least that was the theory that was explained to me many years ago by a few fellas that seemed to know what they were talking about.

December 20, 2010, 01:00 PM	#14
Shoney Senior Member Join Date: February 21, 2002 Location: Transplanted from Montana Posts: 2,311	Straight wall semi-auto pistol brass gets microscopically shorter with each reloading! I have measured brass in 45ACP, 40SW, 9mmLugar, 9X18, and 380 to find that this is true. What causes brass to stretch? As the firing pin hits the primer, the cartridge is pushed forward, the powder begins to burn, pressure builds in the case. At this point, if the pressure is great enough, the case expands outward and grips the sidewall of the chamber, the primer backs out until it hits the bolt face, the case from the web to head stretches as the case head backs out to hit the bolt face, and the primer is reseated. There is an excellent illustration of this in post #6 of this thread: http://thefiringline.com/forums/showthread.php?t=432628 In cartridges that do not have sufficient pressure generated to grip the sidewall of the chamber: The firing pin strikes the primer and pushes the cartridge forward, powder burns, pressure builds, the primer backs out, and almost simultaneously, the case moves backward, and both primer and case strikes the bolt face. The case is ejected without any stretch.

December 20, 2010, 02:08 PM	#15
zippy13 Senior Member Join Date: August 23, 2008 Location: SoCal Posts: 6,442	Guss, If you have an book like the old NRA's Handloading by Wm C Davis, Jr, you'll find the standard dimensions for each cartridge case and chamber in the reference section. In you situation, the .380ACP has a case length dimension of .680(-.010)" in the reference section. With the reloading data it notes that the maximum case length is .680" (which is consistent with the standard) and a "trim-to" length of .673" (which is longer than the .670" minimum permitted in the standard). If you are looking for consistency, as noted by Jim Watson, then set your case trimmer to .673" and and start trimming. Personally, my PPK/S isn't my go-to gun for 50-yard work. If your Fiocchi cases measure less than .670" then they're out of spec. FYI: I just measured some of the cases of the .380ACP's ammo I have. W-W's were in the neighborhood of .675", Fiocchi's around .678", and some commercial reloads were around .687" (well over spec).

December 20, 2010, 07:18 PM	#16
Guss Junior Member Join Date: August 19, 2010 Location: Tampa Posts: 6	Zippy - That's the kind of straightforward information I was after. A person can't be expected to buy a string of expensive books in hopes that one will have the few numbers he is after. I will return to the library and see what they can bring in.

December 20, 2010, 08:03 PM	#17
noylj Senior Member Join Date: October 22, 2007 Location: Between CA and NM Posts: 860	Look for the "trim-to-length" and you can assume that any brass you have that falls below that AFTER resizing is too short. Personally, I save those cases that are within 0.005" of the maximum case length for when I need the highest accuracy (particularly in 9x19). The firing pin actually is hit so hard that it travels a good distance and even my shortest cases have never had a problem being fired. It is good to worry, but if your reloading manuals aren't warning you and the forums aren't warning you, you may be worrying about a non-issue.