Concentricity , what seater die should I get ?

[Metal god]

Accordingly, an expander is required for full length and neck only dies, with or without bushings. Is that correct?

No , technically you don't need an expander button at all with a lot of bullets , boat tail being one of them . Standard FL or neck only dies generally size down the neck WAY more then is needed on the up stoke of the ram . The expander button then resizes/expands the neck to the correct-ish size as it's pulled back through the neck on the down stroke of the ram .

A bushing die both FL & neck uses size ( diameter ) specific bushings that only size down the neck to a specific size/diameter of your choosing .

Example : Lets say you want a .002 bullet hold . You measure the outside diameter of a loaded cartridges neck ( bullet already seated ) and use the bushing that measures .002 smaller . The fact you are custom sizing down the neck to it's final size on the up stroke , there is no need to use the expander button because your neck was not OVERLY sized down like it is using a standard die .

I don't remember the exact number but my standard 308 Redding FL sizing die sizes the neck down something like .010 more then is needed . The expander button then has to resize the neck again as it's pulled out . This is working the brass way more then is needed to accomplish the same task as a bushing die does .

If you don't use the expander on a standard die you likely wont be able to seat flat based bullets at all and when seating BT bullets the bullet it self will be resizing the neck as it's seated likely throwing off concentricity .

I'll go see what the actual diameter my standard die sizes a neck to with out using the expander button .

 

[Metal god]

My standard FL die sizes the case neck down from .342 to .327 that's .015 of movement , because the neck was sized down that much an expander needs to be used to stretch the neck back out . Which when used with the standard die , expands my neck back out to .335 which is another .008 of movement over working the brass IMHO . It is that stretching/expanding that many believe is what throws off the neck alignment with the body . Now cw308 ( a member here at TFL ) has found the opposite to be true and has more concentric necks when using a standard die compared to a bushing die .

My bushing die using a .336 bushing sizes the neck down from .342 to .335 that's .007 of movement clearly showing the bushing die works the brass less on the up stroke and does nothing on the down stroke because it's at it's final size already resulting in not needing the expander .

 

[oley55]

thanks MG, I think I got it.

Without going into great detail about sorting, measuring, and trimming efforts for my 7.62 LC (11) brass (different same year stamps??), using only a caliper to measure wall thickness, I am getting a consistent thinnest wall at .015" on one side and up to .018" on the other side.

So after outside turning I expect to end up at or just under .015". Before reading this thread and understanding what the Lee collet die would do, I had ordered the Forster Precision Plus Bushing Bump Neck Sizer die (not planning to use the bump until it is needed). It comes with three popular sized neck bushings (.336, .334, .332), I am pretty certain I can turn to a size that will work with one of these bushings.

168gr Hornady 308 HPBT= .3079"+.015"+.015"= .3379"- 002"=.3359"(.360"). I plan to process a few cases and seat a couple bullets to see how I'm doing.

As I keep thinking through this process, I have just about convinced myself (ignorance is bliss) that all will not be truly consistent until the newly processed batch has been fired again in it's intend rifle. Then the next neck sizing and bullet seating will produce much more physically consistent reloads.

 

[cw308]

Hi Guys , just chiming in . I went back in my notes . Using the Standard F/L RCBS Sizing die , my fired Federal cases OD on neck .342 case thickness averaged .014 - 015 Sized neck OD ..333 my expander ball measured .306 With the bushing dies I sized the necks down in two steps was suppose to help in runout , the case body with the bushing setup was like two different units working together , never worked well for me .With the standard full length die is one unit the only wiggle room is I leave the expander shaft with alittle wiggle to self center the ball in the neck , I lube the inside of the necks with a Q tip to help guide the ball through the neck . Bought a Hornady Concentricity gage to check runout , used alot when I was using the Redding Bushing S type dies . Full length sizing with the standard dies I hardly use it , my runout is average .001 .Seating with the Redding Competition Seating die , which I used also with the bushing dies , so my problem was coming from the sizing .I only shooting 200 yards so runout may not be noticable , you most likely are shooting long range . Hope I added some in some way .

Chris