Thread: Shoulder Bump Advice

Originally Posted by grandpamac

Greetings,
The tight spot on the shoulder in the chamber may not be where your comparator is measuring so go with the measurement where the case chambers freely. There is one thing to watch on belted cases is a tight spot developing on the body of the case just in front of the belt. This is due to loose tolerances for chambers and dies. The case can chamber with resistance but the shoulder is well short of the chamber. From your description you don't have a problem. Be thankful, others are not so lucky. Check your cases each load for signs of head separation as this can be a problem with belted cases. Cases grow in length when FL resized. The diameter of the case is reduced and with the press ram hard up its bum there is nowhere else for the brass to go, don't worry about it. Just trim to the right length. There are a number of reasons for cleaning and lubricating the inside of the case necks including keeping the necks concentric. Cases stretching due to a lack of lube is an old fable that refuses to die. Frequent tests have disproved this fable but it lives on.
Being an OCD type of chap I do decapping, case sizing and neck expansion as three different operations. De capping the case with a punch set allows the primer grit to be kept away from the die. Expanding the neck from the outside in with the standard button keeps the neck straighter than some standard dies. John Barsness did a test on this a while back. Keep asking questions and developing your skills. There are no stupid questions.
Regards Grandpamac.

"The old fable " thing may occur , I don't like to discount any possibility but not to the degree often quoted . Hence , my advice regarding sizing with the expander removed to eliminate that as the cause . It's often easier to appease the doubters than battle with them and I don't like to give the impression of being a know it all , I'm not .
I started a thread on the subject , even with a visual demonstration on YouTube some still thought it witchcraft .

I agree with the above, my experience differs. It easy to try and discount if no improvement.


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Originally Posted by PipIstrelle

"The old fable " thing may occur , I don't like to discount any possibility but not to the degree often quoted . Hence , my advice regarding sizing with the expander removed to eliminate that as the cause . It's often easier to appease the doubters than battle with them and I don't like to give the impression of being a know it all , I'm not .
I started a thread on the subject , even with a visual demonstration on YouTube some still thought it witchcraft .

Greetings @Piplstrelle,
Mostly for my own benefit a short test was carried out. Two once fired .308 cases, previously fired in the .308 were selected and deprimed with a punch set. Case lengths were measured with one at 50.9mm and the other 50.92. Both measured 42.17mm on the comparator with the .375 inch chamber (I don't have a .400 inch one). Case 1 was sized with the expander assembly removed and a +0.006" shell holder. Case length grew to 51.18mm. The second case was sized with a dry expander replaced. It measured 51.15mm. This was without any neck lube and took quite a bit of force. Last the first case was neck expanded with the expander button, just in and out. Case length was now 51.5mm same as the second case. Both cases measured 42.22mm with the comparator and chambered snug.
This test pretty well agreed with what I had read elsewhere ie: Case stretching takes place when the case is sized and not when the neck is expanded. Expanding the neck shortens the neck and case slightly. Case shoulder length in the comparator was slightly longer after sizing so the shoulder was not set back. The Winchester cases had previously been fired in a test on powder speeds done a few years back. They had produced low single digit velocity variation and excellent accuracy. QED.
Regards Grandpamac.

.2 of a mm give or take..so a flyshit more than a zigzag rice paper......

Originally Posted by Micky Duck

.2 of a mm give or take..so a flyshit more than a zigzag rice paper......

A gnats whisker indeed Micky. Still 0.2mm works out to 8 thou in the old money or most of the tolerance between max and trim to length for cartridge cases. Those of us that use light loads and neck sizing in cartridges like the .222 or .303 never have to worry about it. Regards Grandpamac.

But had the brass been fired multiple times without annealing?

With old hardened brass it makes a huge difference if you’re short on lube inside the neck.

Maybe on softer brass not so much


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2.1230 sounds like the one, no need to resize smaller than you need to.

Originally Posted by Dicko

But had the brass been fired multiple times without annealing?

With old hardened brass it makes a huge difference if you’re short on lube inside the neck.

Maybe on softer brass not so much


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Greetings @Dicko,
The brass was once fired and Winchester brass. This is some of the thinnest brass and it was not FL sized before loading. its only prep was to chamfer the inside of the mouth. Any case mouths with dings have the expander button run in and out of the mouth. My brass is annealed after every third firing, after every firing for target brass. The test cases were not annealed to remove one more variable. To me the evidence is clear.
Regards Grandpamac.

Clear but perhaps not relevant GPM if the OP has brass that has been used several times, and is brittle.

You size it down based on individual rifle chamber specs and then alter the specs as you almost flip the bench over trying to get the case out of the fls die. The brass is now over size. A bit of lube and some annealing fixes this.

I’ve had it happen with both .270 and .257 AI brass.


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Around the third firing, no annealing as of yet.
Interesting to see some suggestion to size to 2.1230" to avoid working the brass, when this is quite a big change compared to post firing at 2.1200".
Cheers for all the suggestions, I am reading them!

Originally Posted by Sonicjoe

Around the third firing, no annealing as of yet.
Interesting to see some suggestion to size to 2.1230" to avoid working the brass, when this is quite a big change compared to post firing at 2.1200".
Cheers for all the suggestions, I am reading them!

It may be worth annealing 2 or 3 cases and fire forming to get a better picture of your chamber dimensions . Unlike rimless cases that stretch from the shoulder backwards to the boltface, rimmed magnums stretch forwards from the rim first .
Not all brass comes from the factory annealed , some are annealed mid' forming .