Case Head Expansion

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gman3

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Would .004 expansion on the belt, and web area just forward of the belt from new brass, to once fired raise any eyebrows? Never have really paid any attention to it before, but issues with a new rifle has made the micrometer come out.

I haven't had an opportunity to check from once fired to the second firing yet. I've always read that expansion of half a thousandth in the web area indicates pressure problems.

Any thoughts?
 
Would .004 expansion on the belt, and web area just forward of the belt from new brass, to once fired raise any eyebrows? Never have really paid any attention to it before, but issues with a new rifle has made the micrometer come out.

I haven't had an opportunity to check from once fired to the second firing yet. I've always read that expansion of half a thousandth in the web area indicates pressure problems.

Any thoughts?
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Any thoughts?

Yes, .004” case head expansion on the first firing is too much. Problem, few measure before and again after. I have found belted case heads that had expanded .016”. The same case head expanded .008” at the extractor ring. The cases would not fit an RCBS #4 shell holder. I fixed that, I used a small case friendly ball peen hammer. Of the 440 cases 40 had been abused, I offered to reduce the diameter of the case ahead of the belt with a collet in a lathe and I offered to cut the extractor groove. That did not change the fact the cases fit the shell holder before loading.

There is a similar thread running on another forum. A reloader needs to know where to start and learn to compare. In the big inning, before the Internet, reloaders purchased new factory over the counter ammo. They measured the diameter of the case head before firing. Normal case head expansion for good cases was said to be .00025”. When loading the same cases the reloader wanted to maintain the the .00025” case head expansion.

If case head expansion was greater the reloads were consider hotter than factory loads.
 
In my reading and research, I determined that .001" indicates high pressure. I have measures many, many revolver cases before insertion into the cylinder and remesured just after removal. 99.9% showed no expansion (heavy loaded .44 Magnum, (neck sized so case head area wasn't sized down smaller than cylinder diameter). I have one instance where I had an over load of True Blue in a .357 Magnum w/160 gr. SWC. The loads were hot enough to loosen the primers (they dropped out when I opened the cylinder!) and IIRC, cases were .003" over spec, but I had not measured prior to firing, and I ain't gonna try that load again...:D
 
Would .004 expansion on the belt, and web area just forward of the belt from new brass, to once fired raise any eyebrows? Never have really paid any attention to it before, but issues with a new rifle has made the micrometer come out.

I haven't had an opportunity to check from once fired to the second firing yet. I've always read that expansion of half a thousandth in the web area indicates pressure problems.

Any thoughts?

Are we talking about factory loads, new brass, once fired, full length sizing, what caliber?

How was extraction? What do the primers look like? Any headspace?
 
Any headspace?
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How much head space? Or clearance, or what is the difference between the length of the chamber from the shoulder to the bolt face and the length of the case from the shoulder of the case to case head?

Then we should ask; how would clearance effect the case head when fired or how would clearance upset the case head?
 
.257 Weatherby, factory Weatherby ammunition. Fired one time. The primers were slightly flattened, but the velocity was lower than expected, and the accuracy was poor. The brass also has a shiny ridge just forward of the belt.

I'm thinking the rifle has an overly large chamber. I may do a chamber cast so I can get an accurate measurement of the chamber dimensions, freebore etc.

I will probably shoot it again tomorrow. The difference is from a new unfired round, and after firing. These are not handloads. I do have some handloads which I am going to try.
 
I'm thinking the rifle has an overly large chamber. I may do a chamber cast so I can get an accurate measurement of the chamber dimensions, freebore etc.

I think your right. A chamber cast is a very good idea.
 
Just about an hour ago I finished reading an article in the 10-14 issue of Handloader magazine. This method was used by Ken Waters in developing some of his Pet loads...15/10,000 was his max expansion from new brass,
to fired reloads. this was measured on the case head or on the belt for CHE (case head expansion)or PRE (Pressure ring expansion) which was measured just above the extractor groove on the web. It`s a good article, and easy to understand. He describes how to back down the load to develop the most accurate load with the highest velocity.
 
I'm thinking the rifle has an overly large chamber. I may do a chamber cast so I can get an accurate measurement of the chamber dimensions, free bore etc.
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What effect would a large chamber have on case head expansion? My case heads are not supported and for the most part my case heads protrude from the chamber, then there is the radius.

I have a limiter when sizing cases, I call it the shell holder. My shell holder will not allow the die to size the case head. My shell holders have a deck height of .125”.

Then there is one of those ‘and then’ moments. The belted case head spaces on the belt. If that is true the case ahead of the belt is supported, or is it?
 
Are you measuring the CASE HEAD, you know, the part below the extractor groove/belt, or the pressure bulge above the case web? Very different animals, since the case head should have NO expansion and almost all cases will show a pressure bulge above the extractor groove about ¼".
Clarification is needed.
 
Post #7

Sorry, I didn't read post #7 before posting about The Ken Waters method...However I`ve read it twice now, (post #7) and it keeps getting more confusing.

Too much info ...my arm started to go numb after scrolling 18 pages..

I believe the Waters method is a whole lot simpler, and a lot less confusing.
 
I tried the Ken Water case head measurement technique and came to the conclusion he was selling snake oil.

I consider positive indications of high pressure: pierced primers, leaking primers, sticky extraction and expanded primer pockets. Other indications, such as flattened primers, not as reliable but an indication something is going on.
 
Case expansion

Measuring accurately at .0015? With what equipment? How many of you guys have equipment and sufficient technique capable of repeatably measuring in that range? Repeatably is the operative word.

Sometimes I have to scratch my head and wonder.
 
slamfire, I totally agree!!! I don`t shoot max loads in anything anymore.
I`ve learned to back off when I get a sticky extraction or maybe a really flat primer. I don`t feel the need to load to borderline dangerous conditions anymore...I started keeping a notebook for my reloads back in 1972...I started out with a Lyman Spartan press and all American dies in 30-30 win , and 222 Rem in 1970, or 1971...back then if you pierced a primer or flattened the primer, or couldn`t read the headstamp, you just backed off a couple grains, and started over.

I still believe in loading manuals, and I like to check 2 or 3 for a given bullet and powder load.

I don`t hunt anymore...bad hips, but I still like to go to the range and shoot!
 
I'm using a Starrett outside micrometer 0-1". The case head, below the extractor groove and the belt expanded from .5298 to .5335. The area just above the belt, (with the mic butted against the belt) went from .5091 to .5161. The case body at the shoulder radius grew from .4893 to .4942.

It is new factory loaded cartridges in Weatherby brass. I'm not trying to use expansion to guess the pressure of hand loads.

Maybe this is a normal result of fire forming.

I'm sure the shoulder moving forward a bit and getting larger in diameter along the case body, back to just above the belt is quite normal and to be expected.

Its the expansion of the belt and the web area that I wonder about.

Again, these are not hand loads.
 

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Measuring accurately at .0015? With what equipment? How many of you guys have equipment and sufficient technique capable of repeatably measuring in that range? Repeatably is the operative word.

Sometimes I have to scratch my head and wonder.
Click to expand...

I have lots of tools that will measure much more accurate than one and a half thousandths. OD is the most simple tool of all a regular micrometer will get you into the tenths of a thousandth. For reloading all you would need is a 0-1" but they make them hat will measure much larger OD's as well.

This is a 0-24" set

IMG_20150105_141304_010_zps3b8e6ae7.jpg


If you are trying to measure say neck thickness to .0001" you would use a different style micrometer that can handle the radius.

IMG_20150105_113038_076_zpsb7d8bb3a.jpg


For bores, bore mics are what you need for that kind of precision.

IMG_20150105_155220_620_zpsf1a1c311.jpg


If you have standards and learn how to use them you can do better than .0015 with regular calipers.

IMG_20150104_133015_996-1_zpsbabb46c4.jpg
 
- Blown primers (all the way out): 20-25,000(+) psi too high [Immediate Stop]
- Ejector marks: 15-20,000 psi too high [Immediate Stop]
- Loose pockets after 2-3 firings [8-10,000 psi too high [drop charge 5-6%+]
- Loose pockets after 5 firings 3-6,000 psi too high [drop 2-4%]
 
Dang it JM, that just looks WAY too much like work to be posting up on a weekend.....;)

Yep use those quite a bit and have for 30+ years. You can get down to the frog hair if you have a good feel for the equipment you work with. I get a little iffy sometimes though measuring ID's on things getting up over about 15-20" and bigger though. Something about finding that perfect center on that wide flat radius of a wear ring or pump case...
 
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