What would cause this on cases?

[Guest Lester Weevils]

Was sorting last week's range pickup brass and noticed these odd cases. They are not from my pistols. I know what my firing pins look like and I was shooting mixed brass.

Randomly picked up about 300 cases near my shooting station and quit because it was getting dark, and I only shot about 150 that day.

The cases that look like this, are at least 50 RP cases and at least 20 FC cases. No other brands have these markings. The firing pin marks look like they all came from the same gun.

I don't think they are reloads. Maybe they are somebody's mixed brass reloads and the fellow only had FC and RP to reload. But I don't think they are reloads because the FC primers are noticeably flatter than the RP primers. Dunno if Federal always uses Federal primers in its factory ammo, but Federal primers seem more likely to flatten even on modest loads.

Unless the guy was a reloader and he went to the trouble of using different brand primers on the different brand brass, then it seems most likely that the fellow was shooting factory ammo out of two boxes, both Remington and Federal, out of the same pistol?

Am guessing that this artifact was made by the pistol and not from reloads with oversize bullets or whatever? This is uncleaned brass, two example RP's on left and two example FC's on right. The entire lot looks just like these examples--

Below the "bullet line", the case diameter is ever so slightly larger than above the bullet line. Can barely feel the bullet line with a fingernail. I measure about 0.006" difference on most cases but am not very good with a caliper.

It probably ain't a glock, because the firing pin indentation ain't rectangular? The RC primers are not flattened and the FC primers are not absurdly flat so it doesn't seem likely that the cases experienced unusual pressure.

Are they 9mm Luger shot from some kind of non-9mm pistol?

Maybe the guy's pistol has rifling extending all the way to the chamber, hanging onto the bullets for awhile before the bullets get moving?

A chamber with a "step" machined in it?

A sloppy big chamber?

Or something else entirely?

[mdmoseley]

prob shot thru a glock

[DWARREN123]

Never saw that before. It is strange.

[Guest 6.8 AR]

Looks like the gun might have been chambered for something else.

[glockster157]

I am not sure what you are asking. The lines in the cases look like factory roll crimps. Your right in that Glock uses a rectangular firing pin and these were definitely not shot in a Glock. It could be a line in the chamber but that would be very rare....but not impossible.

[Guest Lester Weevils]

Thanks all for the ideas.

Maybe it is some kind of homebrew cannelure, but doesn't look like any factory cannelure I've seen. All the factory cannelures I've seen have a "dimpled" appearance from a "gear-like" knurling bit, and even the cannelure tools sold to reloaders feature that kind of dimpled knurling bit. Been trying to talk myself into buying a cannelure tool and spent way too much time web-searching about them.

This line is a simple sharp-edged very small diameter step.

Web-searching cannelures, a couple of internet warriors were speculating that maybe one could make a cannelure tool out of can-opener parts, but no one reported actually making one. A cannelure made with a can-opener rotary cutter or a simple edge-sharpened steel washer could perhaps make that kind of line. Dunno.

The firing pin marks are very consistent and tidy. Tidier than some of my pistols' firing pin marks, so it maybe it is not just the result of a total piece-of-carp cheap gun?

Edited January 8, 2012 by Lester Weevils

[SonnyCrockett]

clean it , load it and shoot it....

[deerslayer]

clean it , load it and shoot it....

+1

Size a few and see what they look like.

[1gewehr]

Very strange! I'll vote for a sloppy chamber. It might be that the finish reamer didn't get all the way to the end of the chamber. I notice that some of the cases appear to have marks on the case mouth that look like they might have had trouble getting fully chambered.

[myg30]

If they were reloaded they might have crimped the brass smaller than nessary causing the gap for gas to get by.

Could be sloppy chamber, old war pistol maybe.

Clean em size em reload em !

Mike

[Guest Lester Weevils]

Thanks all for the good ideas. It is doubtful that this slight step-ring is big enough to have fatigued the brass. I have no doubt that they will reload just fine.

Was just curious what may have caused it. Before posting I did too much web-searching looking for similar pictures but all I found was base-bulges from unsupported chambers. And drastically-resized or ruptured brass from idiots shooting 9mm in .40 guns and such. It would seem almost impossible to shoot 9mm in a .40 at all, much less not notice it!

Anyway, these cases don't show evidence of any bulges on the bottom, so it doesn't seem related to an unsupported chamber.

Too tight crimp, finish reamer not going all the way in, old war pistol. All sound reasonable. Thanks!

One thought-- Have often wanted a 9mm revolver but S&W quit making them before I got around to buying one. Can't recall ever seeing a 9mm revolver in the flesh.

My .357 revolvers have a step inside the cylinder chambers. Reckon a 9mm revolver might have an intentional step in the cylinder holes for some reason?

[SonnyCrockett]

now THIS I would worry about.......nice 40SW case huh? LOL DANG QUITTER

[MarkInNashville]

They almost look like factory crimps. I have no clue why they are there but I have seen them on various new, factory ammo. I just went and pulled a handful of polished cases out of my bin and found a Winchester case that has it. After you reload them a few times the marks will work themselves out and you wont see them any more.

[Guest Lester Weevils]

They almost look like factory crimps. I have no clue why they are there but I have seen them on various new, factory ammo. I just went and pulled a handful of polished cases out of my bin and found a Winchester case that has it. After you reload them a few times the marks will work themselves out and you wont see them any more.

Thanks, Mark

It may very well be a factory crimp. I too see them on some 9mm. It seems that such crimps are most likely found on defense 9mm.

However, all the factory cannelures I've seen have a dimpled appearance similar to the picture below, but less extreme. This is a Corbin example picture of a "don't over-do it, this it is too extreme" crimp from a Corbin cannelure tool that I've been lusting after--

link-- Corbin HCT-1 Hand Cannelure Tool

[MarkInNashville]

It may be. I can't say that I have ever seen them as pronounced as that Corbin round, I'm looking at some Glaser Pow'rball in 9mm and they aren't.

[Guest Lester Weevils]

It may be. I can't say that I have ever seen them as pronounced as that Corbin round, I'm looking at some Glaser Pow'rball in 9mm and they aren't.

Thanks Mark

I agree. Have never seen any factory cannelure as deep as that picture. The Corbin web page claimed that the picture is an example of "way too much crimp". Maybe they were also trying to demonstrate that the tool has the ability to work from "too little" all the way up to "way too much".

All the factory cannelures I've seen had a light "band" with a noticeable width, rather than just being a very thin line. And all of the factory crimps I've seen had a dimpled or gear-shaped impression in the narrow band, rather than a very thin clean sharp line.

Have you seen some factory crimps that are just a single narrow line? With no "knurling pattern" in the cannelure?

A couple of weeks ago was trying "very carefully" to see if I could make slight cannelures in some .380 reloads where the bullets setback too easy. Tried a bunch of tools in the toolbox to see if a few rounds could be acceptably done without buying or building a cannelure tool. I tried several electronic crimpers and a fairly heavy-duty ethernet connector crimper, and several big pliers. I got the most passable result VERY gently applying some large diagonal cutters. But the big diagonal cutters made a very thin-line crimp, and I saw why they probably use a narrow-band Knurler rather than a sharp edge. Even a shallow narrow-line crimp looked to me like it might work the brass too much and maybe weaken it.

[BigK]

I'm curious, do you think it's possible someone loaded these rounds pretty hot and shot them using a moonclip out of a revolver?

Or maybe they shot Luger ammo out of a pistol chambered for Makarovs?

[Guest Lester Weevils]

I'm curious, do you think it's possible someone loaded these rounds pretty hot and shot them using a moonclip out of a revolver?

Or maybe they shot Luger ammo out of a pistol chambered for Makarovs?

Thanks BigK

Those explanations sound reasonable as far as I know.

If shooting the luger in a Makarov, wouldn't they be shooting with the pistol out of battery? Or if the Makarov pistol is a blowback gun maybe it wouldn't be crazy dangerous? Am totally ignorant of Maks except knowing that the case is 1 mm shorter. The guy apparently managed to shoot at least 70+ rounds without blowing himself up.

Never seen a 9mm revolver (but would like to have one). Was earlier wondering if a factory 9mm revolver made these case marks.

Just now googled conversion of .357 cylinders for 9mm moonclip. Didn't find a bunch of detail. Ferinstance Pinnacle does that, but apparently Pinnacle does not offer a detailed step-by-step description of their process--

Pinnacle-Guns.com: Pinnacle High Performance Custom Gunsmithing

Found a forum thread with a guy explaining that in order to "do it right" requires boring the back of the cylinder to allow the 9mm case to fit, and sleeving the front of the cylinder chambers to better guide the shorter-case bullet to the forcing cone. Dunno if Pinnacle does both steps.

It might be complicated to conical bore the cylinder to fit a 9mm case? Given a special-made 9mm conical bore bit it would be simple, but on the other hand it might be a hassle to do it right with with a lathe?

So maybe the simple solution that would work just as good as a conical cut-- Partially bore a short section of the back end of the cylinder holes so that the wide back-end of the 9mm case will fit in the cylinder?

That is a lot of speculation, but ought to result in the "step" observed in the cases?

[BigK]

Yeah, I was just throwing ideas out there...no clue really.

FWIW...the Taurus 905 and S&W 940 and 547 are some factory 9mm revolvers.

The only reason I thought about the revolver idea is that I've seen similar marks on a .357 case after a bunch of 38 specials have been fired out of the gun first. Like I said, though, I have no clue.

Very interesting. Hope someone chimes in with a 'real' answer. I'm kind of anxious to know what the deal is.

[Jonnin]

as for shooting a 9 in a 40 --- in a lot (most??) of guns, the extractor claw is strong enough to hold a "close" round in place long enough for the firing pin to hit it. For example you *can* fire a 380 in a 9mm this way, though it will sometimes get hosed up due to the claw not holding it (bullet slides on in the chamber), cannot cycle the gun of course, and may jam up due to the short case length. But it will work often enough for those who are intent on screwing something up to get a few shots off. It is probably possible for a .40 to hold a 9mm in place well enough to do the same thing, if someone were determined to make it happen. The diameter is not THAT different and all it takes is one good hit on the primer, even the edge of it. Its 1mm bigger around, if that, and a primer is about 1mm wide, so it should be possible to nick the edge of it in some guns under some circumstances.

[Dave Shooter]

Lester,

one other possibility is an intentional "annular ring" in the chamber. Some mostly obscure 9mm blowback pistols had this to help delay extraction till pressure dropped.

[MarkInNashville]

I was explaining to a coworker why this site is so good, as he was asking me questions about reloading for a riffle (of which I have never done). It dawned on me what the crimp MAY BE for... Please keep in mind - wild ass guess (WAG) here! Since a 9mm indexes off of the mouth of the case they don't want to put a taper crimp in it, to ensure it works in a wide variety of firearms (least they get bad-mouthed on some message board, after all) but they absolutely do not want to allow the bullet to compress into the case (exploding and of course, being bad-mouthed on some message board), so the perfect compromise would be a crimp on the base of the bullet.

IDK, just a guess.

[glockster157]

That is one of the ways to crimp a case to avoid bullet set back. Set back does cause higher pressures and can be very dangerous. Reloaders normally use a taper crimp on rimless pistol cases as cannelure crimps can be hard to do and take special tools.

[Guest Lester Weevils]

Lester,

one other possibility is an intentional "annular ring" in the chamber. Some mostly obscure 9mm blowback pistols had this to help delay extraction till pressure dropped.

Thanks Dave

Even if obscure, that might be the most likely explanation for the case markings? Didn't know that some pistols have that design feature. Perhaps even obscure factory pistols would be less rare than bored-out converted revolver cylinders?

That is one of the ways to crimp a case to avoid bullet set back. Set back does cause higher pressures and can be very dangerous. Reloaders normally use a taper crimp on rimless pistol cases as cannelure crimps can be hard to do and take special tools.

Yes cannelures seem most prevalent on high-power revolver loads, though they are found on some 9mm. Looked thru my .380 brass and found a few FC, Star, and Corbon cannelured cases.

It is said that cannelures are useful on high-power revolver loads to keep recoil from jostling the bullets loose. One wouldn't think that recoil would be likely to cause much of a setback problem on a fullsize 9mm pistol, but maybe it would be more significant on pocket pistols?

[Guest FroggyOne2]

Well looking at the primer, there was not very much pressure on the primer, this indicates a soft or light load.. my thinking that these were indeed reloads do to the roundness of the primer in the cases. And hence since these were very light loads, there is the great chance that the expanding gas excaped around the mouth of the brass before the brass had the chance to seal up the chamber as the bullet was exiting the case into the thoat of the barrel. Now I know what your thinking, if it were the case that it was a truly light load, you would have noticed that possibly the guy was experiencing malfunctions due to the lack of blowback action in the pistiol.. unless it is a revolver. But as a person being aware of this, could have changed the recoil spring in the gun. But I am also thinking, why would this person have left the brass laying, unless it was bought from a dealer of some sort that sold reloaded ammo.. Still there would be the thought of malfunctions of a pistol with light loads, unless he has a soft spring or a spring that lost some of its resilience and is barely cycling and clearing the fired brass from the chamber.. Just some thoughts running around in my head on this one.