Neck inflation after firing 223 Wylde

A

arpcentralone

New member
Well, title says it all pretty much. I know they Wylde chamber is different to some degree to a more accurate 223/5.56 combo. After firing some homebrew loads through it, I notice that all my casings have an inflated, somewhat mid-way belled appearance to the necks. I know it will come out when I resize, but this seems a little excessive and may work the neck too much. Extraction is fine. Anyone experience this with a Wylde?

I tried taking some pics but it's kind of hard to focus on such a minute perspective.
 
I kind of want to get a chamber mold poured but I'm afraid it may not come out if there is a concave (for lack of a more intelligent word) neck section. I don't see it with some dimensional wylde drawings.
 
The Cerro-Safe metal that you make a chamber cast with melts at roughly boiling water temp.
If it did somehow get stuck,you can melt it out.
 
Yeah, I got 4x 1/2lb ingots to play with of that stuff. Just haven't worked up the nerve to melt it and pour it down my chamber. :rolleyes: If something can go wrong, especially with my luck, you know it will.
 
Yeah, we both fell from the same tree, at the same time, and landed in the same thorn bush, then rolled into a salt bath. It was quite miserable for both of us. :p
 
If the neck is unevenly expanded in any way, there's a problem with your chamber.
Be advised, if the chamber neck really is "somewhat mid-way belled appearance to the necks", the chamber cast may end up locked in place by this.
 
I would find someone with a borescope and check this out if you can't or won't do a chamber cast. I agree that the cast could get wedged in the chamber, but it would not be forever. To me, it would be in tune with knocking out a stuck bullet or similar to slugging a barrel.
 
The other way is to drop a rod of pure lead into the bore and hammer it to fill out the chamber with a CRS rod and hammer. This is how Veral Smith recommends checking a chamber and throat. It is unlikely the neck is actually belled inside though. The design of the reamers is such that in order for that to happen the fat area would have to be carved out by chips and would be very rough. Marks on the necks of fired brass should show it.

The ballooning may be natural, especially if the load is very mild so the shoulder of the case doesn't expand very hard. When the gun fires, the neck expands but the taper of the shoulder makes it a little more rigid at its corner with the neck. Also, if the case has been reloaded multiple times, an internal donut ring may have formed there from brass flowing into it from the shoulder during resizing, and that would make it more resistant to expansion, too. The expansion of the neck rolls forward from its lowest point of contact with the bullet bearing surface. As it nears the mouth of the case, gas starts to leak out at the mouth, dropping pressure between the brass and bullet, so the case mouth never expands. It is very common, if the chamber neck is not too large, to find you cannot push a new bullet freely into a fired case's mouth because it never expanded and springs back toward its resized diameter after the bullet goes past it. This is because pressure has equalized around the outside of the case mouth by the time the bullet clears it. This is why you so often see some carbon on the outside of a neck even when the rest of the case sealed the chamber well.

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Wow, nice explanation! The cases resemble the picture you provided, and I believe you have hit the proverbial nail upon the head. There were no rigid signs upon the neck, so I believe my mid range loads using older brass are to blame. I usually spend a day and size and trim all at one. I also just started implementing annealing into my processing of cases.

I am very thankful for your expertise!
 
You are welcome. Here's a complete image of that case, which was once-fired, and an apparently much-used prepped case that has a donut forming and has inside neck reamer marks from the donut having been cut out previously. You can get a sense of how that would reinforce that area after a while. This was not my case; it's a range foundling, so I have no idea what the load level was. The lack of pressure ring thinning might indicate it was loaded mildly, but it might also just mean the chamber was snug and he didn't resize very far or mostly used neck-sizing-only.

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Great stuff there. I wonder if annealing more, like at every reloading, could attribute to the donut ring, since softening that area could allow more brass to flow there. I heard it was safe to anneal often, so long as it's done correctly.
 
Yeah, we both fell from the same tree, at the same time, and landed in the same thorn bush, then rolled into a salt bath. It was quite miserable for both of us.
Click to expand...

I was the guy you two landed on...

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The obvious is the bullet moves forward and hits the lands, hesitates while pressure builds and swells the case, then the bullet continues down the barrel.
Keep in mind the 'Wylde' chamber closes up 'Bullet Jump' (Free Bore) some so bullet is hitting rifling sooner than it would in a 5.56mm chamber.

Two things come to mind, one is the chamber has to be allowing the brass to oversize in the areas indicated. If the chamber wasn't oversize the brass couldn't swell.
I get shouted down every time I suggest chambers should be cut in steps instead of gouged out with a one piece reamer.

The second thing is I'd watch brass from this rifle closely. This has to be overworking the brass at a point that commonly splits anyway.
A good argument for annealing, but for brass that didn't take a lot of prep (flash hole, primer pocket sizing, neck turning, etc) I'm not sure I would mess with it...
Probably just load/shoot a few times & discard when cracks started to show up in the batch.

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Uncle Nick has some GREAT stuff!
I have seen exactly what he shows with the mouth curling inward, and it's often more pronounced on roll crimp cases. Don't ask me why the roll crimp would make it curl more, but it seems to.

That's a great cut away comparison between once fired & loaded several times.
It really shows what goes on when the brass is loaded several times, and particularly when the brass is loaded 'Hot'.
 
I think the roll crimp just has more spring-back.

JeepHmmer said:
The obvious is the bullet moves forward and hits the lands, hesitates while pressure builds and swells the case, then the bullet continues down the barrel.
Click to expand...

But not quite in that order. Very close though. Decades ago now, H.P. White Laboratories did some detailed measurements of the firing event in high power rifles. They found the bullet doesn't even begin to move (measurably) until the general pressure measurement is at least 10,000 psi or so. Other even earlier measurements by Dr. Lloyd Brownell with strain gauges put it at more like 12,000 where you can see a brief hesitation in the pressure rise as the case expands to chamber size. The bullet still has to accelerate, and it often doesn't finish the jump to the lands until the pressure in the chamber is closing in on halfway to the peak value. When the bullet hits the throat, it initiates a pressure wave due to plugging the pressure up momentarily, and you can see it on a strain gauge instrument trace pretty easily. In any case, the brass is swollen up before the bullet gets to the throat unless it starts there or very, very close to it. The curl on the case mouth proves the rest of the case is expanded by the time the bullet is fully released, though it may already have started to slip in the neck by then.

It would be fun to do a detailed animation of it.
 
I think that would depend on the bullet to case interference fit.
Since you can unseat most bullets with an inertia hammer that produces way less than 10,000 psi equivalent, and die forming the bullet to the rifling can indeed take 10,000 psi to do, I have to believe it's often the bullet hitting the rifling that causes a pressure spike.

I can't tell you myself since I don't have that Superman X-RAY vision...
 
Oh, it's not that it needs anything like that kind of pressure to make it move. The force on the base is then around ten times normal bullet pull. The reason it's that high is the very short time frame. The inertia of the bullet is the source of the reaction force that keeps it from moving appreciably before the pressure gets up there.

Incidentally, I think you are right about cutting chambers in smaller steps. Roughing reamers are expensive, but if you find a worn finishing reamer you can get it resharpened maybe three thousandths undersize and start a chamber with it. I wonder what the rental places do with their retirees?
 
I notice that all my casings have an inflated, somewhat mid-way belled appearance to the necks.
Click to expand...

I would suggest you measure the neck diameter at the bulge and then measure the neck diameter ahead and behind the bulge. I have cast chambers for a different reason than most. I have used Dake arbor presses when checking barrels with odd and or unusual chambers, same for Wilson case gages.

I have used hammers, drifts and new cases when determining the diameter of chambers. To keep Murphy our of it never forget to lube the case.

F. Guffey
 
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