RCBS Neck sizers bumping my shoulder a few thousandths??

[jwc1080]

What would cause my neck sizer die to push my shoulders back? A once fired case measures 2.265, a reized case measures 2.258, a twice fired case 2.261. I turned the sizer die 1/8th turn down from contacting the shell holder. I only fired one reload loaded with the starting load for my 210s. Case looks fine to me. I'm just worried I overworked those 15 peices of brass and may have a premature case head seperation.

 

[Red hunter]

Are you putting any lube inside case neck? What is you fired case length compared to max case lenght? The once fired may be long and bottoming in the die???? The expander ball may be shortening the case when it goes into the case if it's not lubed??? That is my WAG.

 

[jwc1080]

I angled the Hornady One Shot when I sprayed the bodies of the cases so the inside was lubed. I can feel the expander ball enter the case mouth when sizing with very slight resistance, so I don't think thats it. I'm not sure that the overall max case length is on a .300WM. Does it vary on each chamber? I'm reloading factory hornady cases.

 

[Red hunter]

Max case legth is 2.620 on the 300WM. Back you die out. I set my neck dies so the die just touches the shell holder and see what happens when you size one. I Have a couple neck dies that don't touch at all but neck size just fine. After sizing it make sure it is correct OAL and head space then try to chamber it. If it chambers and all measurements are good you are set. IMO

 

[Gene]

If you want to neck size only, keep the die up far enuf that it will size about 80% of the neck only. That will not bump the shoulder back. And, the 20% that is not sized will provide a good alignment of the case with chamber.

 

[jwc1080]

I'll back the die out on the remaining cases. How will i know the neck is sized correctly? Should i expect to see short case life in the the cases where the shoulder was bumped?

 

[Gene]

The neck is sized correctly circumferentially if there is enuf tension to hold the bullet securely. A loaded round should be about .002" larger at the neck than an sized round after bullet is seated.

Eventually case necks will split from sizing many times. You can make them last longer by annealing necks only.

 

[Red hunter]

I would only do a couple of them till you get a set up that is working the way you want it.

 

[Bart B]

I agree that the die may not have been set high enough in the press.

I do not agree that a larger case neck diameter at the back of the neck helps center it in the chamber neck. On fired .300 Win Mag cases that are only neck sized, it's their shoulder that centers them in the chamber shoulder when fired. Case necks float in the chamber neck and don't touch the chamber anyplace when fired. Most of them center that way before they're fired anyway when the bolt's closed on them.