Redding Bushing Dies: How to Select the Proper Bushing
Looking for a simple explanation of why we use bushing dies, or how to select the proper bushing for your Redding Type S, or Redding Competition Neck Sizing die? Here’s my take on it.
The advantage a bushing die has over a standard die is the amount of stress placed on the case neck as it’s sized. A standard full-length sizing die is machined to size a case to standard dimensions, regardless of case thickness. As far as the main body of the case goes, that’s no big deal. Once it’s fired to fit the chamber, the main dimensions of the case don’t change much in a die, even a full-length non-custom die. The problem is the neck.
To accommodate a wide range of varying brass thickness from brand to brand, and end up providing an inside diameter that will securely grip a bullet, a standard die uses two steps. First, the case is forced into the neck portion of the die and sized down, then it’s pulled back over an expander to set the final diameter.
In order to work with cases that are relatively thin, the interior dimension of the neck portion of the die is on the small side of neck diameter specs. That can be tough on brass, especially if it’s thick brass, like Lapua. It tends to cause concentricity problems, hardening of the brass, and muzzle velocity inconsistencies.
The bushing die eliminates the second step, and allows us to size the outside diameter of the neck to precisely where we want it. I prefer and recommend the Redding Type S FL sizing die. Click HERE to see why.
What diameter should the neck be sized to? I’ve had consistent success with brass that is sized .001” to .003” smaller than the loaded round’s outside diameter. This is commonly known as neck tension.
I now aim for .001” neck tension when working up a load. It provides enough grip to securely hold a bullet, is easy on brass, and doesn’t induce runout on a sized neck. Some of my older recipes still use bushings that squeeze the necks .002” or .003”. They work well, too.
I’ve tested different tensions within the same load, and even neck-turned some 260 Remington brass to see what difference it made.
I’ve found that as long as I don’t go over .001” of neck tension disparity, I can’t measure the difference. For example, .001” to .002” doesn’t affect anything, but .001” to .003” does. Neck turning has made no difference. I sort new cases for .002” or less thickness runout, but don’t turn them as a rule. I’ve since tested that process on a 7 WSM and 300 WM with similar results.
I concluded that the overall thickness of the brass was more important than small thickness variations when choosing a bushing.
To determine which bushing to use, you need to know what brass you’re going to use and how thick it is.
This is important. Brass can vary as much as .003” across different brands of the same cartridge case. The difference in thickness between Lapua and Remington 260 Remington brass is .002”.
The easiest way to measure for a bushing is to load a bullet in the brass you’re using and measure the outside diameter with a digital caliper. Subtract .001 and order that number bushing. For example, if my loaded round’s neck diameter is .294”, I’ll order a .293 bushing.
If you don’t have a loaded round, you can measure the case neck thickness, multiply it by two, then add the bullet diameter. For the round we just measured, it would look like this:
Neck thickness= 0.015”
Bullet Diameter= 0.264”
Neck Thickness (x2) + Bullet Diameter = Loaded Round Diameter
0.015”(x2) + 0.264” = 0.294”
To get an accurate thickness value, a ball micrometer works best. You can use a caliper, but because you’re measuring a curved surface with a flat anvil, it won’t be accurate. Mine come out .0015-.002” thicker when using calipers.
For reference, here are some of the cartridges I loaded last year, the brass I used, and the Redding bushing number:
- 260 Remington/ Remington brass/ .288 bushing
- 260 Remington & 260 Terminator/ Lapua brass/ .293 bushing
- 300 Winchester Magnum/ Winchester brass/ .333 bushing
- 7 WSM/ Winchester brass/ .312 bushing
- 338 Edge/ Remington brass/ .364 bushing
I’ve only had one Redding bushing not match the dimension it was marked for. It was off by .001”. I ordered another one of the same size that was spot on. There are tolerances in everything, I guess. Don’t try to measure the bushing with your internal caliper jaws—it’ll be inaccurate because of the radius. Just size a case with it and see where you end up. These numbers are all relative anyway, and results on target are the ultimate measurements!
Check out this short video demonstrating how to measure for the proper bushings:
Here are some other things I do and have learned while using Redding bushing dies:
- I use the plain steel bushings and lube the cases with Hornady One-Shot Case Lube before sizing.
- I remove the decapping rod and expander from the Type S dies. An expander IS NOT needed when using a bushing die.
- Don’t get wrapped around the axle about the exact amount of neck tension. Pick a value between .001” and .003” and run with it.
- I’ve tried the bushings number up, and number down in the die. I insert the bushings with the numerical marking facing up. That makes it easy to look down in the die with a light to check which one is in it.
- I clean my sizing dies before starting a big batch. I squirt a little One-Shot into the clean die before the first case gets sized, then leave it alone.
- Keep notes on all bushing/die/brass combinations used, and always check the bushing number before sizing.
- A Redding bushing die will not size the entire neck. Because of how the die is machined, it’s impossible. There will be a portion of the neck close to the shoulder that never gets sized. It’s normal. I set mine up so the bushing just barely self-centers in the die before locking the nut down.
- Brass thickness dimensions vary from brand to brand, but calibers stay the same. If you’re using Lapua brass, you can use one bushing for 260 Remington, 6.5 Creedmoor, and 6.5-284.
- I’ve ordered most of my bushings from Sinclair or Midway.
I think that’s all I have to say about using Redding bushing dies and choosing the proper bushing. As usual, I probably missed something important. Send me an email if you find something or have a question. Remember, results on target are all that matter to me. This is how I do it, but I won’t hold it against someone who does it differently. Question everything and try different methods until you get the results you want!