Incepient case head seperation after 3 loads.

[jerseyjoe]

What does the thickness of the rim measure in different places around the rim?

The reason I ask is that in one of the photos it looks uneven.

SAAMI shows it should be .049" +0.00 / -.010.

I had some new Winchester 45acp brass that was giving me fits trying to get a bullet seated without a ton of runout and large bulge on one side.

I checked every piece of equipment for parallelism, perpendicularity and squareness to no avail.

I finally took the brass and dummy round to work and checked them on an optical comparator, where I found the problem.

The perpendicularity of the case head to walls was way off, even after sizing, and I notice that the rim thickness, undercut and angle above it followed the crooked case head.

Check your brass and see if any of these conditions are present. Stand them on a flat surface and rotate them next to a good square object to see if they are leaning.

 

[Mtstalker]

The thinning is uneven in height from one side to the other and is right on the upper edge of the ridge.

 

[jerseyjoe]

That's kind of the point I was making.

If during the final extruding before machining, the case head and walls end up not pependicular, it will show up in the machining of the rim thickness and undercut and will affect the way the metal flows; ie more metal flow up one side than the other causing a thinning on one side.

 

[Mtstalker]

I ordered some ppu brass and in one of the reviews online they said to decrease load by 10% due to thicker walls. Is that just for military calibers or all? I know with lc theres capacity limitations due to thicker brass but in 270?

 

[jerseyjoe]

Increased wall thickness means less internal volume, so yes, decrease the charge weight.

 

[Mtstalker]

But is that the case with the 270 brass?

 

[fguffey]

I ordered some ppu brass and in one of the reviews online they said to decrease load by 10% due to thicker walls. Is that just for military calibers or all? I know with lc theres capacity limitations due to thicker brass but in 270?

I would weigh a few cases and then compare. I own one military 270 case and I own one R-P 270 case that uses Berdan primers.
I necked down a few 30/06 cases to 270 Winchester, it was not something I had to do because I have all the 270 cases I will ever use. I am not the fan of short cases, I want the case to cover all of the chamber, there is no way a 30/06 necked to 270 Winchester will cover the chamber.

F. Guffey

 

[Mtstalker]

Jerseyjoe i measured the rim and it varys from.048" to .044". I did set some fired and new cases along a 90 degree corner and some looked ok and some looked slightly off but i think the body was straight it was the rim causing this whick would only compound the small brass issue.

 

[rardoin]

Is it just me or does it appear, in the photos, that the case head is not square with the case body? If this is actually present (can be roughly confirmed/ruled out with a small machinist's square) may the bolt face be out of square with the chamber when in battery? Just another thought.

 

[Albany Mountain]

I would do a chamber casting and measure off of it for comparison.

 

[fguffey]

I would do a chamber casting and measure off of it for comparison.

Stopp429, do you have any experience with chamber casting?

F. Guffey

 

[Fbomb]

Have you tried indexing your brass? You can do this when shooting and when reloading. Make a vertical line on the brass with a sharpie. Line this up with a specific place on the gun when you chamber the round. See if the bulge is in the same location in relation to the sharpie mark on each piece of brass. This should show you if the bulge is happening due to imperfections in the chamber. Next time you load this round in the gun rotate it 120 degrees and shoot. See where the bulge is in relation to the sharpie line each time after firing. Rotate it 120 degrees further the next time and compare again. This way you have chambered the round three different ways in relation to the chamber. This will show you if the bulge is always towards one side of the chamber and if it is moving. You can do the same thing when sizing the brass.

 

[Brians356]

The thinning is uneven in height from one side to the other and is right on the upper edge of the ridge.

You can see in that section that you are nowhere near an incipient separation. There's still plenty of thickness remaining at the thinnest spot, and what you see is not uncommon in SAAMI chambers. If you sectioned a case nearing failure, it would make you break out in a sweat.
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[Brians356]

Have you tried indexing your brass? You can do this when shooting and when reloading. Make a vertical line on the brass with a sharpie. Line this up with a specific place on the gun when you chamber the round. See if the bulge is in the same location in relation to the sharpie mark on each piece of brass.

The bulges are likely in the same orientation on every case, but that will not prove the chamber is out of round or otherwise defective. The way the extractor puts pressure on the chambered case, or even gravity I suppose, could ensure every case is cocked in the chamber in the same orientation. I will wager a tidy sum the chamber is not out of round.

And once a case has been fired once, and bulged on one side, even after FL sizing it is likely to assume that same cocked position in subsequent firings, so the bulge shouldn't "walk" around as case/chamber orientation rotates. A standard FL die (against a standard shell holder) will likely not iron out the original bulge completely.
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[Mtstalker]

Lol i will! i have one a buddy shot that is cracked 98% around ill cut it open. I have not casted a chamber but ut doesnt look too hard.

 

[fguffey]

I have not casted a chamber but it doesnt look too hard.

Stopp429, correct, there is only one way to do it correctly, that leaves two shooters/smiths/reloaders that know how, as strange as this may sound: I trained him. The one thing I learned from all of this is: It is not possible to discuss chamber casting on the Internet/a reloading forum.

F. Guffey

 

[Brians356]

"On this ship there are four ways to do things: The right way, the wrong way, the Navy way, and my way."

"Captain Queeg" (Humphrey Bogart) in "The Caine Mutiny"

 

[Mtstalker]

I will put them up against a square tonight if i get time.

 

[jerseyjoe]

This is the image that caught my eye.

Notice how the angle leading away from the undercut to the case wall is longer/wider on the top than on the bottom. (assuming it's not a camera angle problem).

The only ways this can occur during machining is if the mandrel it is on is running out or the case head and web is angled (not perpendicular) to the centerline of the cartridge, a problem that may have occurred on the draw prior to machining.

Assuming the latter, the top of the case would be leaning toward the side of the case with the widest angle.

@fguffey: I was a tool & die maker for 11 years at Cerro Metal/Cerro Fabricated Products (Cerrosafe's namesake) and have poured easily over 1000 casts of die cavities with check metal (what we called it) for inspection purposes.

May I enter your exclusive club of people that can pour a cast of a slightly tapered round hole and measure it accurately?

 

[Mtstalker]

I see. And it makes perfect sense i have only used this one batch of brasss in this rifle. When the new stuff comes in i will index and shoot to see if it happens. I did find 1 box of factory win to shoot as well. I loooked at my 243 win brass and some has this as well just not as severe. I sorted them out and it out of the hornady fed and rem brass that is mixed together only the winchester has these slight marks. So that is making me think its a brass problem with winchester. I have some rem brass in my 243 with 8 reloads and they look just fine. Crappy part is i have 400 peices of new win for my 243.