Thread: Shoulder Bump Advice

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.

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 .

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.