How much should the neck portion of the die be sizing the brass? My case necks before sizing measure .296 outside diameter and after sizing measure .283. The inside measure .266 before sizing and .253 after sizing. Then the expander sizes them to .261. I feel this is why my necks are splitting. It's a 6.5 prc.
Dies
- Thread starter sako2
- Start date
Standard dies are designed to put enough sizing on the thinnest neck the cartridge drawing allows for. The average neck is thicker and is over-resized by it, so the expander is needed to correct for the over-resizing. From the SAAMI drawing, the neck has a 0.004" thickness tolerance, which is 0.008" in diameter. That is, the neck over a seated 0.2644" bullet can be 0.289" to 0.297". Since your case necks are 0.296" before resizing, and allowing for 0.001-0.002" of spring-back from the chamber size, your chamber is not loose. It will accept maximum diameter cartridges. The die is designed to reduce a 0.289 case with a -0.004" thinner wall and have it spring back out some. You are correct that this overworks the brass. How much depends on your actual wall thickness. The best way to find that is to measure the neck over top of a loaded bullet whose diameter you have measured before loading it.
There are four cures.
One is to get the neck of your sizing die honed out by the 0.008" to remove the extra steel (assuming you aren't going to change to a different brand of brass with a different neck thickness later). RCBS and Forster both offer this service for their dies, IIRC, but I think RCBS only does it when you are ordering a new die from them.
A second approach is to buy a neck bushing type resizing die and buy a neck bushing the right size for the neck to come out only as wide as you need it to be, thus only lightly rubbing the expander. Indeed, you really need no expander with this unless your case mouth is dented and needs rounding on the way to the neck bushing. Even then, the next size smaller expander is usually adequate for dent removal (a 6 mm expander in this case).
The third is to use a Lee Collet Die to size the neck separately and a separate Redding body die for resizing the case below the neck in a separate step.
The fourth is to outside turn your necks down by 0.004" to fit them to the current die. That's more brass removal than is normal in one step, so it might take several passes and does weaken the neck's hold on the bullet, altering start pressure. It is the least attractive of the alternatives to me. Also, thinner brass will expand more in your chamber, to the amount the brass is being worked doesn't change; just the direction of it does. But it will lessen the expander drag.
There are four cures.
One is to get the neck of your sizing die honed out by the 0.008" to remove the extra steel (assuming you aren't going to change to a different brand of brass with a different neck thickness later). RCBS and Forster both offer this service for their dies, IIRC, but I think RCBS only does it when you are ordering a new die from them.
A second approach is to buy a neck bushing type resizing die and buy a neck bushing the right size for the neck to come out only as wide as you need it to be, thus only lightly rubbing the expander. Indeed, you really need no expander with this unless your case mouth is dented and needs rounding on the way to the neck bushing. Even then, the next size smaller expander is usually adequate for dent removal (a 6 mm expander in this case).
The third is to use a Lee Collet Die to size the neck separately and a separate Redding body die for resizing the case below the neck in a separate step.
The fourth is to outside turn your necks down by 0.004" to fit them to the current die. That's more brass removal than is normal in one step, so it might take several passes and does weaken the neck's hold on the bullet, altering start pressure. It is the least attractive of the alternatives to me. Also, thinner brass will expand more in your chamber, to the amount the brass is being worked doesn't change; just the direction of it does. But it will lessen the expander drag.
jetinteriorguy
New member
I’ve been using UN’s third option for a few years now and it not only extends case life but with a Forster seating die has kept runout to .001” or less consistently.
big al hunter
New member
Uncle Nick covered the die solutions pretty well. I am wondering if you have been annealing your case necks? This would soften the brass, preventing splitting. Just another option if you are already happy with the results you are getting for accuracy.
Thanks for the response's guy's. Yes big al I've been annealing after every firing and still loosing case's after every firing do to split necks. That's why I started looking at the die I'm looking into this die.sizing.https://www.precisionreloading.com/cart.php#!l=WHID&i=SIZSB65PRC
scatterbrain
New member
My number one reason for annealing was to prolong the life of hard to get brass. I seldom throw away brass now for split necks. The problem now is loose primer pockets.
That die or the Redding S die is available at the same source for a few dollars less. It's also a bushing type. Either should be good quality.
I am surprised the annealing didn't help. Be sure you don't overheat during annealing. If you get it too close to visible red, it actually weakens the brass.
I am surprised the annealing didn't help. Be sure you don't overheat during annealing. If you get it too close to visible red, it actually weakens the brass.
Unclenick the adg brass comes annealed from the factory. After the 1st firing when I resized the cases I thought I was going to rip the press off the bench pulling the expander through the neck. I didn't start annealing them until the necks started splitting. 300 win mag cases size easier. I sized a case yesterday without the expander and it was much easier. That case measured . 252 inside the neck the expander measures .261. Even after annealing the cases were hard resizing. I ordered that die and 2 bushings a .290 and a .291.
jetinteriorguy
New member
Have you tried lubing the inside of the necks?
I know it may be mixing apples and oranges, but my two lots of ADG .308 Win brass have walls that are 0.014" thick. So I was wondering how you measured yours? Calipers tend to have poor precision measuring the ID of small holes due to the small flats on the inside of the jaws (see illustration below). Getting a number that is low by one or two-thousandths is pretty common measuring holes in the bullet diameter range. A big diameter hole or the distance between two pins or flats is what those ID jaws do better. I either use a pin gauge on the inside of a case or use a small hole gauge for a transfer measurement to an OD thimble micrometer or just measure the OD of a bullet and seat it and measure the OD of the neck over top of it and divide the difference by two, as I described before.
OK. So its thick. Not quite SAAMI maximum (0.0163"), but thick. The bottom line is just too much over-resizing, so the solutions I listed before still apply. The only other thing I can think of to look at is how close the top of the expander is to the neck portion of the die. You can adjust that on some designs by changing the decapping pin position, and if it gets too close to the neck, the brass gets jammed between the expander and the die shoulder trying to come out. That would also weaken the case. Setting the decapping pin a little deeper would change the feel if this is the case.
That said, something pulling that hard on a neck can stretch the shoulder forward and cause a chambering problem or pull the neck off the case centerline, so stopping the problem is a good plan.
That said, something pulling that hard on a neck can stretch the shoulder forward and cause a chambering problem or pull the neck off the case centerline, so stopping the problem is a good plan.
I use the hornady headspace comparator and set the shoulder back .002. I lubed the inside of the necks made it easier but still hard. The expander is down about a 1/2" from the neck sizing portion of the die. I sized a case without the expander in the die. It measured .252 inside diameter. The expander measures .261.