EDG
01-22-2015, 03:22 PM
Multiple sizing passes and brass rotation during sizing
Grumpa mentioned this technique in another thread. I think it is used by more than a few people but is not more widely used because people cannot see the benefit without good measuring tools and techniques.
I have been using the multiple pass brass rotation technique for FL case sizing for maybe 30 years. What I found was my ammo seemed to shoot better. Later I acquired the Hornady caliper mounted case gauge and found why my ammo shot better. The shoulder was in exactly the same location on every round.
If you resize your brass with one quick workman like stroke you have a "mess" of variables that you are adding to cause variation in the case shoulder location. You cannot detect these variations unless your bolt gives hard chambering now and then. People do not understand why some cases are tight and others are not so they just screw down on the FL die until it goes away and they are happy. At least that is what I did for a long time. When I formed fired 30-06 to 25-06 I always had a few tight cases.
I had a project about 5 years ago to form some .303 British cases to 6.5X53R Dutch Mannlicher brass. I had exactly 100 new cases that I was going to put a lot of trimming and forming effort into and I did not want to lose a single one. (Now with today's brass prices no one wants to ruin a single new case if they can avoid it.)
To form the .303 cases I pushed the shoulder back in several diameter steps. Then the cases were formed with a trim die - I had NO reloading dies.
A few old crappy once fired 303 cases were formed and trimmed for a particular purpose.
1. Several cases were trimmed short a few thousandths and were used to set the length of the shoulder when doing the final sizing. This was carefully tuned to .000 clearance in the rifle chamber. I could feel a light drag with each dummy case in the chamber. Because they were trimmed short the neck length could not interfere.
I wrote down this measurement for later reference.
2. Then several cases were left long but were formed back to the finished shoulder length. These would not chamber due to the case mouth hitting the end of the chamber. I carefully trimmed and tried until I found the chamber was 1mm or .040 longer than the case specification.
Once I had all of this information recorded I started forming the new .303 brass. I pushed all the shoulders back and measured what was going on. I finally got to the last step. Before forming the last few thousandths in the trim die I trimmed all the cases to the exact length of my chamber minus .002.
Then I started the final forming with the trim die. I measured each case with the Hornady tool and tried each case in my rifle as I went. This was very slow and tedious but I learned a lot. I found that the amount of lube on the case and how well it was distributed affected the shoulder location. I found that the speed of the sizing stroke affected the shoulder position - too fast left the case long from head to shoulder. If I did not let the press dwell at the top of the stroke for 3 or 4 seconds the case might vary. If I did not make multiple passes it might vary. These variations would be about .002 max with my Rockchucker. Sometimes they were .001.
When I combined all the technique improvements here is what happened.
I used a consistent application of case lube - both amount and distribution.
I used multiple sloooow sizing passes on the same die setting. The multiple passes included rotating the case twice for a total of 3 slow passes. Each of the passes had a 3 to 4 second dwell time at maximum stroke to allow the brass to quit creeping. The early variations, as I experimented and learned, were simply erased by running a case back through the trim die one or more times. Once the lube, speed, dwell and multiple passes were put into the process control, the variation from case to case went to zero. This was verified by the rifle bolt having the same exact light drag on the cases, time after time for 100 cases. This process could not have been perfected without the ability to see very small changes in the sizing process with the Hornady tool.
About the long case necks???
Well the .303 shoulder diameter is smaller than the body of the 6.5 Mannlicher. The maximum length cases went from almost exactly the same length as the chamber to shorter when fired. Most cases were .004 to .007 shorter. I now use 2.145" in my rifle knowing the chamber is 2.150" long. I am not recommending this practice to anyone but that is how I do it for this one rifle. These cases have only been neck sized and fired. I have a set of 6.5X53R Dutch Mannlicher dies now. If I ever FL size these cases they will get longer when squeezed down and will probably require trimming to avoid hanging up on the end of the chamber.
About the neck diameter ???
The neck of the 6.5X53R trim die was .295 or about .010 larger than needed for a loaded round.
All of the cases formed in the trim die chambered at .295 because the rifle chamber neck was .300 in diameter.
When sized for loading I neck sized part of the neck with a 6.5X55 FL die which was .286. There was lots of room for the .303 brass in the Dutch Steyr neck. Early Mannlicher ammo was known for split necks. I think the oversize neck is part of the cause. It shows the need for keeping your brass annealed.
Grumpa mentioned this technique in another thread. I think it is used by more than a few people but is not more widely used because people cannot see the benefit without good measuring tools and techniques.
I have been using the multiple pass brass rotation technique for FL case sizing for maybe 30 years. What I found was my ammo seemed to shoot better. Later I acquired the Hornady caliper mounted case gauge and found why my ammo shot better. The shoulder was in exactly the same location on every round.
If you resize your brass with one quick workman like stroke you have a "mess" of variables that you are adding to cause variation in the case shoulder location. You cannot detect these variations unless your bolt gives hard chambering now and then. People do not understand why some cases are tight and others are not so they just screw down on the FL die until it goes away and they are happy. At least that is what I did for a long time. When I formed fired 30-06 to 25-06 I always had a few tight cases.
I had a project about 5 years ago to form some .303 British cases to 6.5X53R Dutch Mannlicher brass. I had exactly 100 new cases that I was going to put a lot of trimming and forming effort into and I did not want to lose a single one. (Now with today's brass prices no one wants to ruin a single new case if they can avoid it.)
To form the .303 cases I pushed the shoulder back in several diameter steps. Then the cases were formed with a trim die - I had NO reloading dies.
A few old crappy once fired 303 cases were formed and trimmed for a particular purpose.
1. Several cases were trimmed short a few thousandths and were used to set the length of the shoulder when doing the final sizing. This was carefully tuned to .000 clearance in the rifle chamber. I could feel a light drag with each dummy case in the chamber. Because they were trimmed short the neck length could not interfere.
I wrote down this measurement for later reference.
2. Then several cases were left long but were formed back to the finished shoulder length. These would not chamber due to the case mouth hitting the end of the chamber. I carefully trimmed and tried until I found the chamber was 1mm or .040 longer than the case specification.
Once I had all of this information recorded I started forming the new .303 brass. I pushed all the shoulders back and measured what was going on. I finally got to the last step. Before forming the last few thousandths in the trim die I trimmed all the cases to the exact length of my chamber minus .002.
Then I started the final forming with the trim die. I measured each case with the Hornady tool and tried each case in my rifle as I went. This was very slow and tedious but I learned a lot. I found that the amount of lube on the case and how well it was distributed affected the shoulder location. I found that the speed of the sizing stroke affected the shoulder position - too fast left the case long from head to shoulder. If I did not let the press dwell at the top of the stroke for 3 or 4 seconds the case might vary. If I did not make multiple passes it might vary. These variations would be about .002 max with my Rockchucker. Sometimes they were .001.
When I combined all the technique improvements here is what happened.
I used a consistent application of case lube - both amount and distribution.
I used multiple sloooow sizing passes on the same die setting. The multiple passes included rotating the case twice for a total of 3 slow passes. Each of the passes had a 3 to 4 second dwell time at maximum stroke to allow the brass to quit creeping. The early variations, as I experimented and learned, were simply erased by running a case back through the trim die one or more times. Once the lube, speed, dwell and multiple passes were put into the process control, the variation from case to case went to zero. This was verified by the rifle bolt having the same exact light drag on the cases, time after time for 100 cases. This process could not have been perfected without the ability to see very small changes in the sizing process with the Hornady tool.
About the long case necks???
Well the .303 shoulder diameter is smaller than the body of the 6.5 Mannlicher. The maximum length cases went from almost exactly the same length as the chamber to shorter when fired. Most cases were .004 to .007 shorter. I now use 2.145" in my rifle knowing the chamber is 2.150" long. I am not recommending this practice to anyone but that is how I do it for this one rifle. These cases have only been neck sized and fired. I have a set of 6.5X53R Dutch Mannlicher dies now. If I ever FL size these cases they will get longer when squeezed down and will probably require trimming to avoid hanging up on the end of the chamber.
About the neck diameter ???
The neck of the 6.5X53R trim die was .295 or about .010 larger than needed for a loaded round.
All of the cases formed in the trim die chambered at .295 because the rifle chamber neck was .300 in diameter.
When sized for loading I neck sized part of the neck with a 6.5X55 FL die which was .286. There was lots of room for the .303 brass in the Dutch Steyr neck. Early Mannlicher ammo was known for split necks. I think the oversize neck is part of the cause. It shows the need for keeping your brass annealed.