Impressed line around case-problem, or just my OCD?

[CCWdownrangeP2]

Here's a question for all of you. Pistol, straight walled cases that have a line or even two encircling the case (primarily 38, 357mag, 45LC). Simply from an aesthetic standpoint I've never really cared for these. Do these cases have any inherent structural problem due to these impressed lines or is this just my reloading OCD kicking in? I'd sure like to utilize them if I can settle my mind that they're OK.

 

[Sam1911]

Nary a worry. Load them up and shoot them.

 

[buck460XVR]

Here's a question for all of you. Pistol, straight walled cases that have a line or even two encircling the case (primarily 38, 357mag, 45LC). Simply from an aesthetic standpoint I've never really cared for these. Do these cases have any inherent structural problem due to these impressed lines or is this just my reloading OCD kicking in? I'd sure like to utilize them if I can settle my mind that they're OK.

Are you talking the cannelure that some factory ammo has, or something that appears post resizing? If it's the former, its not a concern and as Sam1911 says......."Load them up and shoot them. "

 

[WestKentucky]

Those lines are there for a reason. They allow more expansion at that point. It's neither good or bad as far as reloading. I get mouth cracks before I see issues with the expansion line. Look at steel cased ammo, almost all of it has the expansion line. If it's similar to that, load and shoot.

 

[Walkalong]

Case on the left has no "cannelure". The one on the right does. They load the same, and as you can see, they iron out over time.

 

[WestKentucky]

Expansion line for sure. It helps seal the chamber in low pressure rounds. They are good to go.

 

[CCWdownrangeP2]

Since these expansion lines, or cannelures are from the factory I always thought they were alright to reload, just wasn't sure if these cases held up well over multiple reloads as time went on, so I was cautious about reloading them. Your replies have helped to ease that apprehension, thanks. Now, if only I could get over having one cartridge with a cannelure as I load it in the cylinder and the next doesn't! :banghead: Maybe I'll need to just sort my loads to fill the boxes with only one style at a time. Darn this OCD!

 

[Sam1911]

Well, I have to admit, that's the first time I've ever heard them called an expansion line, or heard any explanation for them at all. I've asked numerous folks over the years and asked here at least twice. No one has ever been able to explain what they were called or what they were for.

So, cool, you learn a new theory every day, I guess.

I don't buy that it does anything of the sort, at all, but it is good to have a convenient name to give them until something better comes along.

 

[tightgroup tiger]

Thought it was to prevent bullet setback

 

[Sam1911]

I have seen some of these lines that were rather strongly impressed into the case and might actually accomplish that ask. Of course, by the time they hit your reloading bench, they're just a ghost line on the case.

 

[Potatohead]

Yea, expansion lines of course. I knew that..



You guys are purdee smart.

 

[WestKentucky]

I asked the question years ago on .30 carbine steel and that is the answer I got, and it is sensible, and theoretically could do both, but for setback I find it hard to believe since I normally see the lines on ammo with bullet cannellure that are crimped into cannellure. Also I have seen these WAY too low on the cases to serve that purpose.

 

[moxie]

They are there to prevent bullet setback in auto cartridges. Revolvers don't experience setback.

On revolver cartridges I've always thought them cosmetic, but maybe WestKentucky has something.

WestKentucky, any source or data for your claim?

 

[Sam1911]

To prevent setback the lines would be crimped into the case below the base of the bullet, so the bullet can't be easily driven back down past that constriction. Some I've seen (just a few) do actually look like they're struck in deep enough to cause a bit of a tightening of the case there and might do the trick.

In revolvers there's actually more of a problem with the bullets "jumping crimp" and pulling forward, locking up the cylinder.

 

[WestKentucky]

My source was my grandfather but I will try to find a published source.

 

[mavracer]

doesn't matter if it's in the bullet or case it's still a cannelure. As to the ones your're seeing way down the case WK, I bet those are 38 special cases and were originally loaded with flush seated wadcutters, which seat deep in the case.

 

[rcmodel]

They are called case cannulure's.

They are there to prevent bullet set-back from rough handling or use in tube magazines.

They may also be used to identify different but similar looking loads.

They were first used when smokeless powder was invented.
Prior to that, the bullet set on top of a case full of black powder and could not be forced any deeper into the case.

Then with small charges of smokeless powder, they could, so the case cannulure came into use.

As applied so lightly today, they may in fact be more decoration then anything.


But they have nothing at all to do with being 'expansion lines'.

Not ethe very deep case cannulures on this old ammo.
Strictly to prevent bullet set-back with the new fangled smokeless powder.



rc

 

[WestKentucky]

I still think the expansion explanation holds at least some water. It would basically be an obturating ring on the case for the same purpose as when used on a projectile. Perhaps not in small calibers, but since my grandpa served the first part of his tour in Korea in artillery, and the second part in heavy infantry, this would make a little more sense for him to have had knowledge of this and apply it to the odd lines on his 30carbine or on my dads 38spl. The third part of his tour he spent picking up the dead after he was wounded in battle.

 

[Hondo 60]

Do these cases have any inherent structural problem due to these impressed lines

No, no problem.
I've always heard the case cannelure was to help prevent bullet setback.
After shootin 'em a few times, that line gets fainter & fainter.

 

[gamestalker]

I think I read about those canelures in my Speer #10 and they explained as being present in factory brass as an added element of prevention for set back, or jump.

Some brass have two, mostly revolver brass, one to band around the bullet, and the other at the base of the bullet.

With AL brass such as 9mm, .40, 45 acp, there is usually only one canelure, which will be placed just under the base of the bullet to prevent it from getting set back during feeding.

I've never heard them termed as expansion bands though.

GS

 

[Blue68f100]

Never heard it called expansion bands.

Always referred to as a canelure to help prevent bullet setback. See it more common on carry ammo.

 

[Walkalong]

It would basically be an obturating ring on the case for the same purpose as when used on a projectile.

The cannelure on a bullet is to crimp into. It has nothing to do with obturation. Obturation is not a big deal with plated or jacketed, but with lead we need the base to obturate and seal the chambers and grooves.

 

[WestKentucky]

Walkalong, read up on the use of obturating rings in mortars and artillery and I think you will understand better about what I meant, especially if you read about what was done with recoilless rifles. It looks like the heavy hitters have used the concept for that purpose for years, but again on a small scale (sporting rounds) it looks like it would be of very little (if any) effect.

 

[rcmodel]

The obturating ring / driving band on mortar, recoilless rifle, and artillery shells are copper gliding metal rings designed slip to fit the bore for loading, then to expand or be engraved by the rifling upon firing.

I did a 6 year stint in the Army shooting heavy weapons including mortars & Recoilless rifles, and teaching others to shoot them.

Completely different concept, execution, and intent then the depressed cannulures on small arms cases & bullets.

Not trying to diss you, or your grandfather, but you are wrong about small arms case & bullet cannulures, and what they are there for.

rc

 

[moxie]

I've done a little work with this over the years. Obturating rings are more commonly known as driving bands. This discussion started out with case cannelures which are indentations in the brass case. Driving bands (obturating rings) protrude from the case. I'm looking at a pair of 30mm dummies and some 20 mm dummies in front of me. The 30mm have a 1/2 inch wide nylon driving band protruding at the base of the projectile. The 20mm has an 1/8 inch soft metal band. The purpose of these bands is to engage the rifling, provide the spin necessary and seal gas behind the projectile. Without the relatively small driving band, the bearing surface of the huge projectiles would be difficult to deal with.

Case cannelures CANNOT function the way driving bands do simply because they are indented. Protrusion is needed for bands to function.

Put simply, case cannelures are just not the same thing as obturating rings or driving bands.