For those that use bushing for neck dies,

what size bushing do I need?

Do I need at least .003 smaller diameter bushing then the loaded cartridge?

Please keep in mind that this is for a 338 R.U.M and I am concerned that the bullets will slide back into the cartridge during recoil inside the magazine box.

Bullet is .338,

The unturned neck wall thickness is .015,

The fired case neck diameter is .370

So this means that .338 + .015 X 2 = .368

Should I trim more off the neck? reasons why I asked is that about 30% of my virgin brass neck wall measured at .013

Thanks for responding.

One of your better sources for this info will be found in "Tech Notes" on the Redding website.

Good luck-

flaco

I don't keep up with the RUMs and I do not have a set of the latest design bushing dies. However the bushing are not able to run to the very bottom of the neck as do the common FL sizer dies.
With a cartridge of considerable recoil and a short neck I would recommend that you err on the side of tighter and you may need to try several bushing sizes.

For the Remington brass in my 300SAUM the .003 smaller bushing worked best. The the Norma brass the 336 works better. Gets a little pricey adding extra bushings but that is what it takes.

What I find with my bushing dies is that I get some spring back in the brass after sizing. This varies a little bit with the physical properties of the brass,(hardness, alloy, etc) typically I will use about .002" smaller bushing than I calculate to get the correct finished neck tension.

Norseman, I would uniform my brass so that all necks have the same finished/loaded diameter and then try the .002, .003 and .004 bushings below the loaded neck diameter. As the brass ages it will loose it's spring, and it will also begin to thicken in the neck area. Because it is a reasonably large caliber I would think that more tension is better from an ignition and accuracy standpoint, however that is just a wild ass guess as each rifle is a law unto itself. good luck and good shooting.

quote:

Originally posted by Norseman:
For those that use bushing for neck dies,

what size bushing do I need?

Do I need at least .003 smaller diameter bushing then the loaded cartridge?

Please keep in mind that this is for a 338 R.U.M and I am concerned that the bullets will slide back into the cartridge during recoil inside the magazine box.

Bullet is .338,

The unturned neck wall thickness is .015,

The fired case neck diameter is .370

So this means that .338 + .015 X 2 = .368

Should I trim more off the neck? reasons why I asked is that about 30% of my virgin brass neck wall measured at .013

Thanks for responding.

see Redding List here Take the measurement from the smallest neck diameter of all your loaded rounds, and pick a busing .003" smaller. If your are going to neck turn, take the measurement after neck turning is done. I would take a guess and say start with the .363" bushing. You will end up buying more then one bushing.

Load up three bullets and measure the outside diameter. Then subtract how much neck tension you want.

For my 270s and 7mm Rem I use .001in, for my 340 Wby I use .007in.

For a heavy hitter like a 300 RUM I'd go up a bit.

I've got the type-s bushing neck sizer from Redding for my 338/378 Wby. Cost me a small fortune (die was custom order) but it works like a charm. In the past I had problems with insufficient neck tension, even after annealing, when I was doing full or partial sizing with the full length RCBS die that I've got. Since I switched to the Redding, that's all in the past. Occasionally I'll have to run the cases into the FL sizer to set the shoulder back slightly, and I'm sure you'll have to do the same at some point (if you're using the neck sizing die), but other than that, they're an excellent piece of equipment. Obviously this will vary from case mfg. to case mfg. but I use a .361 bushing on my 338/378. I purchased a .359 bushing just in case the tension problem ever returned, but I've never had to use it!

I was just on the Forster site and they supply 3 bushings with their bushing die which would cost quite a bit less than buying a redding and then buying the bushings.