Neck Sizing Bushing

[R. G. Amos]

For those who use only neck sizing dies or full length body sizing dies including neck sizing bushings, how do you determine the size of the neck sizing bushing. How many thousandths do you back off of the desired final bullet seated neck diameter.

 

[bigedp51]

I'm a big fan of Forster non-bushing full length dies and get the least neck runout with them. Too much of what benchrest shooters do with their custom rifles with tight neck chambers filters down to the people with off the shelf factory rifles. When you reduce the neck diameter .005 or more with a bushing die you will induce neck runout. This is why it is recommended to reduce the neck diameter in two steps to prevent induced runout using a bushing die. A bushing floats in the die and can move from side to side and even tilt. On top of this if you do not neck turn your brass you need to use the expander to push the neck defects to the out side of the case neck.

Also at the Whidden Custom Die website they also tell you they get the least neck runout with their non- bushing dies.

Sorry for raining on your parade but bushing dies with standard SAAMI chambered factory rifles in my opinion are a waste of money. The case neck expands to much when fired and reducing the neck diameter with a bushing die increases neck runout.

I would rather buy a Forster full length die and have the neck honed than use a bushing die.

Bushing Dies and Honed Full-Length Sizing Dies
http://bulletin.accurateshooter.com/2012/11/bushing-dies-and-honed-full-length-sizing-dies/


Neck Tension — Not Just Bushing Size
http://www.accurateshooter.com/technical-articles/reloading/neck-tension-not-just-bushing-size/

TECH TIP: How to Select the Right Bushing for your Neck Die
http://bulletin.accurateshooter.com/2009/05/tech-tip-how-to-select-the-right-bushing-for-your-redding-neck-die/

NOTE, if you look at a Forster bushing bump die for the caliber rifle you have they list 3 bushing sizes that come with the die. The different size bushings compensate for varying neck thicknesses of the cases you might buy. Example below.

Forster Precision Plus Bushing Bump Neck Sizer Die with 3 Bushings 308 Winchester
Bushings included: 0.336", 0.334", 0.332"


Forster Precision Plus Bushing Bump Neck Sizer Die 3 Bushings 308

 

[bigedp51]

R. G. Amos

Below is a average Remington .223 case with .004 neck thickness variation. Cases like this are not worth neck turning and if sized with a bushing die the expander must be used to push this type neck defect to the outside of the case.

Below neck turning a case like above is a waste of time, as you can see below the case even after neck turning the case is not centered with the axis of the bore.

The best results from a neck bushing die are with a tight neck chamber and high quality brass like Lapua. And again the average shooter does not need a bushing die and they might even increase your bullet runout.

 

[Ivan the Butcher]

There are a lot of opinions about why or why not to use neck tension / bushing dies. There didn't seem to be much info on how to pick which size bushing to use.

1) Start with a fired case from the gun you are going to be using.
2) using a tube wall micrometer (or caliper) measure the wall thickness of the neck.
3)now measure the outside neck diameter.
4) Now the math: 2 times the neck thickness plus the bullet diameter, minus the desired neck tension (usually 2 to 5 .000ths")
5) Now you subtract step 4 from step 2, and you have the amount the neck will expand when you fire the round.

An old trick for excessive chamber neck diameter is to size the neck only half to 3/4 of the length. This leaves an additional shoulder to help center the cartridge in the chamber.

I use Redding Bench Rest dies for many of the precision cartridges. The Micrometer adjusters help (but are not a necessity) with getting the length of the neck sized and the bullet seated from the lands a specific distance. These help in peak accuracy tuning of ammo for that one gun/case/bullet combination. Change one component and start over!

This is all a lot of work and expense, but done right the results are often astounding. On the other hand, good normal die reloads, with good charge weight control can produce sub MOA accuracy in many if not most rifles at 100 yards. That is about 1" groups at 100 yards, the is about 4" at 400 yards! One MOA at 400 yards will kill most things bigger than mice! But if sub MOA is your quest, here you go! (I like my Varmint and Target guns to be in the 1/4 MOA area or better) All it takes is money and time, and more money and usually more money and time.... you get the ides.

Ivan

 

[10mm_Shooter]

Redding says - .002 for their "S" type titanium nitride bushing... example with LC brass and Sierra match 168gr HBTM I use .336 bushing for desired .338 final diameter