Stripes/Creases in brass

cek · September 30, 2009, 09:08 PM

My son & I were loading up some 9mm tonight and he asked what the stripes/creases on some brass were for and why some have it and some done. I had never thought about it.

Anyone know?

drail · September 30, 2009, 09:11 PM

It's called a cannelure and it serves to prevent the bullet fron seating any deeper in the case.

cek · September 30, 2009, 09:21 PM

I'll buy that. However,

Why don't all cases have them? Cost? I'm guessing the brass without came from cheaper ammo?

For almost any 9mm bullet I've encountered a bullet seated that deep would result in a really, really short OAL; far shorter than any reloading data I have. Is it just an extra saftey measure?

csmsss · September 30, 2009, 10:38 PM

Quote:

Why don't all cases have them? Cost? I'm guessing the brass without came from cheaper ammo?

The cannelure is to prevent something called setback, where the forceful impact of the bullet into the feed ramp pushes the bullet deeper into the case. This has the effect of reducing case capacity, thereby raising chamber pressure when the bullet is fired - which can be a potentially very dangerous situation, depending upon how deeply into the case the bullet has been driven.

You will typically see cannelures in auto pistol cartridges with light-for-caliber bullets - for example, you might see them used in .45 ACP loads with 185 grain bullets. The lighter the bullet, the shorter it will be, and the greater potential for setback.

cek · September 30, 2009, 10:49 PM

csmss, I totally understand the concept/theory. Makes total sense.

However, the cannelure on all of my 9mm cases as well as .45 cases (at least those that have them) is far below where the base of the bullet would actually be in the case. A setback would still push a bullet pretty far back in the case before it hit the cannelure, stopping it.

I would think these increased pressures (especially in 9mm where pressures can get very high quickly with some powders with only small variations of OAL) would still be very bad.

brickeyee · October 1, 2009, 11:03 AM

Quote:

However, the cannelure on all of my 9mm cases as well as .45 cases (at least those that have them) is far below where the base of the bullet would actually be in the case. A setback would still push a bullet pretty far back in the case before it hit the cannelure, stopping it.

With the original bullet?

cek · October 1, 2009, 03:48 PM

Quote:

With the original bullet?

Yea, I think so. I looked at some factory rounds and I just can't believe the bullet reaches that far down in the case.

griz · October 1, 2009, 04:15 PM

They're longer than you think. Here is one loaded and unloaded.

HiBC · October 2, 2009, 02:42 AM

I recall ordering some bulk 9mm bullets,maybe Win's,that were hardball with an open base.The jacket extended past the lead a ways,like a hollow base formed by the jacket cup.This bullet was longer than it's weight would lead you to believe.

brickeyee · October 2, 2009, 03:15 PM

Quote:

Yea, I think so. I looked at some factory rounds and I just can't believe the bullet reaches that far down in the case.

Pull one apart and measure.

As noted above you may be very surprised.

Russ5924 · October 2, 2009, 05:58 PM

I have found them on my .38 and .357 in different makes.

spleify · October 3, 2009, 01:12 AM

Im not sure that everyone is understanding the OP's question. In the original post he is showing a pic of the grooves on the EXTERIOR of the case. Is seems like most replies are about the cannelure on the bullet(correct me if I am wrong). I have no answer as to why or what the small grooves are on the exterior of the case, but they are not on the inside of the case( at least not on the ones I looked at of mine)

brickeyee · October 3, 2009, 12:34 PM

Quote:

Im not sure that everyone is understanding the OP's question. In the original post he is showing a pic of the grooves on the EXTERIOR of the case. Is seems like most replies are about the cannelure on the bullet(correct me if I am wrong). I have no answer as to why or what the small grooves are on the exterior of the case, but they are not on the inside of the case( at least not on the ones I looked at of mine)

No, we know exactly what he is looking at, and what we are saying.

The cannelure on the case is also on the inside, at least till the round is fired and forced against the chamber wall (thousands of PSI will do that to brass).

cek · October 3, 2009, 01:38 PM

Quote:

The cannelure on the case is also on the inside, at least till the round is fired and forced against the chamber wall (thousands of PSI will do that to brass).

On the one's I've looked at so far (all previously fired) I can clearly see that the cannelure extends on the inside.

I would find it discongruous for the cannelure to NOT extend inside an unfired piece of brass. Given the stated (above) purpose of the cannelure is to prevent the bullet from seating too deeply if slammed against a round in the chamber, the feedramp, or something else while feeding you would expect it to HAVE to exist inside the case BEFORE firing.

cek · October 5, 2009, 09:22 PM

Of course the experts on this forum are right. They are always right. That is why this is such a great forum. Thanks for helping to educate my son & I:

We pulled a Federal Hydrashok 124gr 9mm round and discovered that the bullet is, indeed, quite a bit longer than the Rainier TMJ bullets we are reloading with. As the picture below clearly shows the original bullet would seat all the way down to the cannelure.

ballardw · October 7, 2009, 02:07 AM

I have some old 38 special brass that actually has two cannelures. The deeper matches the flush-mouth seated 148 wadcutter and the other is about right for 158 SWC.

The choices for which cases get them probably does vary. In the case of the 38 special wadcutter loads, very little bullet actually protrudes from the case but lots of these were shot in semi-auto S&W's and any additional set back would seriously affect the pressure curve and accuracy of the match loads.

September 30, 2009, 09:08 PM	#1
cek Member Join Date: July 12, 2009 Posts: 87	Stripes/Creases in brass My son & I were loading up some 9mm tonight and he asked what the stripes/creases on some brass were for and why some have it and some done. I had never thought about it. Anyone know? __________________ "My Constitutional right to bear arms is, to me, the most significant example of my American heritage of individual freedom and human dignity. Such a right implies that my Government trusts me and, in turn, is worthy of my trust." - Charles E. 'Ted' Kindel (My dad), Gun Digest #19 1965

September 30, 2009, 09:21 PM	#3
cek Member Join Date: July 12, 2009 Posts: 87	I'll buy that. However, Why don't all cases have them? Cost? I'm guessing the brass without came from cheaper ammo? For almost any 9mm bullet I've encountered a bullet seated that deep would result in a really, really short OAL; far shorter than any reloading data I have. Is it just an extra saftey measure? __________________ "My Constitutional right to bear arms is, to me, the most significant example of my American heritage of individual freedom and human dignity. Such a right implies that my Government trusts me and, in turn, is worthy of my trust." - Charles E. 'Ted' Kindel (My dad), Gun Digest #19 1965

September 30, 2009, 10:49 PM	#5
cek Member Join Date: July 12, 2009 Posts: 87	csmss, I totally understand the concept/theory. Makes total sense. However, the cannelure on all of my 9mm cases as well as .45 cases (at least those that have them) is far below where the base of the bullet would actually be in the case. A setback would still push a bullet pretty far back in the case before it hit the cannelure, stopping it. I would think these increased pressures (especially in 9mm where pressures can get very high quickly with some powders with only small variations of OAL) would still be very bad. __________________ "My Constitutional right to bear arms is, to me, the most significant example of my American heritage of individual freedom and human dignity. Such a right implies that my Government trusts me and, in turn, is worthy of my trust." - Charles E. 'Ted' Kindel (My dad), Gun Digest #19 1965

October 1, 2009, 04:15 PM	#8
griz Senior Member Join Date: July 31, 2000 Location: Middle Peninsula, VA Posts: 1,588	They're longer than you think. Here is one loaded and unloaded. Last edited by griz; October 2, 2009 at 08:20 AM. Reason: Changed photo

October 2, 2009, 05:58 PM	#11
Russ5924 Senior Member Join Date: February 18, 2005 Posts: 1,874	I have found them on my .38 and .357 in different makes. __________________ Russ5924

September 30, 2009, 09:11 PM	#2
drail Junior member Join Date: February 2, 2008 Posts: 3,150	It's called a cannelure and it serves to prevent the bullet fron seating any deeper in the case.

October 2, 2009, 02:42 AM	#9
HiBC Senior Member Join Date: November 13, 2006 Posts: 8,287	I recall ordering some bulk 9mm bullets,maybe Win's,that were hardball with an open base.The jacket extended past the lead a ways,like a hollow base formed by the jacket cup.This bullet was longer than it's weight would lead you to believe.

October 3, 2009, 01:12 AM	#12
spleify Senior Member Join Date: August 3, 2009 Location: Denver, Colorado Posts: 151	Im not sure that everyone is understanding the OP's question. In the original post he is showing a pic of the grooves on the EXTERIOR of the case. Is seems like most replies are about the cannelure on the bullet(correct me if I am wrong). I have no answer as to why or what the small grooves are on the exterior of the case, but they are not on the inside of the case( at least not on the ones I looked at of mine) __________________ ΜΟΛΩΝ ΛΑΒΕ NRA Member Survival Paracord Wraps & Bracelets Like us on Facebook

October 5, 2009, 09:22 PM	#15
cek Member Join Date: July 12, 2009 Posts: 87	Of course the experts on this forum are right. They are always right. That is why this is such a great forum. Thanks for helping to educate my son & I: We pulled a Federal Hydrashok 124gr 9mm round and discovered that the bullet is, indeed, quite a bit longer than the Rainier TMJ bullets we are reloading with. As the picture below clearly shows the original bullet would seat all the way down to the cannelure. __________________ "My Constitutional right to bear arms is, to me, the most significant example of my American heritage of individual freedom and human dignity. Such a right implies that my Government trusts me and, in turn, is worthy of my trust." - Charles E. 'Ted' Kindel (My dad), Gun Digest #19 1965

October 7, 2009, 02:07 AM	#16
ballardw Senior Member Join Date: September 19, 2008 Posts: 1,411	I have some old 38 special brass that actually has two cannelures. The deeper matches the flush-mouth seated 148 wadcutter and the other is about right for 158 SWC. The choices for which cases get them probably does vary. In the case of the 38 special wadcutter loads, very little bullet actually protrudes from the case but lots of these were shot in semi-auto S&W's and any additional set back would seriously affect the pressure curve and accuracy of the match loads.