Case neck runout problem?

Neck thikness is not even all around.
Yes lapua is good, but there is still some little imperfections. If you want to use a bushing neck die without expander ball, be aware that being sized on the outside, all imperfections are inside the neck.

This is why necks must be turned true at all the same thickness before to use a bushing die
 
168bergersapper said:
Insite, Im getting .001- .008 run out and using an RCBS rock chucker press
Click to expand...

Buddy of mine had the same problem with a rock chucker press. You could see the ram move when the handle cammed over. We returned it to the Cabelas he bought it at and took these videos of their display model:






He replaced the press with a CoAx and his runouts dropped to under 0.002
 
Tips I give customers that get bushing neck dies from me...

Outside neck turn - brass flows, so even if the case is even now.. it will not be in a firing or two. As was already mentioned, bushing push neck defects to the inside and into the lower portion of the necks, and that can cause all manner of problems in the seating process. Turning your necks often (ie every firing or two), gets rid of this problem AND added bonus to stopping donuts from forming

If you have a standard shouldered angle case that doesn't flow, either your pressures are low or your necks are hard like a rock.... one is ok. the other, not so much

Annealing - brass work hardens with each firing. PROPER annealing keeps the brass elasticity consistent so you have a chance as consistent neck tension. Consistent neck tension is the point of all these fancy die and steps. If you are not willing to do it properly, don't do it at all.... it is far easier to screw this up then do it right and then you are chasing ghosts.

Shellholders - make sure the case has lots of play in the shellholder... Yep, the case has to wiggle so it can center in the die. The die is what controls case alignment. The only thing the SH does is let you extract the case.

Press - sorry, but there is quite a bit of stuff outsourced and sometimes QC is not good. You want the ram on the press to travel in a straight line. A little play is normal and needed but moving in a curve is bad.

Keep the stroke length as short as possible.. the further that ram can move, the more it can move out of alignment. I much prefer a press with as little "intervention" as possible. Simple is good for precision. Some of the most accurate dies can be used with a "mallet"..... Ironically, some of the least expensive presses work the best.

The mounting of the press should support the entire circumferance of its footprint. Some new presses are bolted at the rear and will actually HINGE with operation... how this can lead to consistency is beyond me.

Simplify, measure each step, correct what is wrong... stuff that works the best don't always cost the most.

YMMV

Jerry
 
".329 is wayyyyy to much. I think you found your problem."

As mentioned, .002" smaller than loaded neck diameter is correct.

Regards,

Peter
 
The root of this problem is not the reloading die itself, it's the amount of resizing you are doing.

When you have a chamber neck diameter that is close to the loaded round neck diameter, the case does not need to expand very far when discharged before it gets support from the barrel chamber. Unless someone butchered the chambering job, your fired case will have no run out. So let's suppose the chamber neck is .002" larger than the neck of the loaded round. You fire the round and the neck expands .002". Now you resize the neck... You only need to reduce the neck diameter by .002 to .003 to hold a bullet. In this case you are not changing the size of the neck very much between firing and resizing. As a benefit of this efficiency you minimize the amount of work hardening of brass and you reduce the opportunity to induce run out as a result of the resizing process. I mean seriously... you cant possibly end up with .003 run out when you are only resizing the neck .003.

Now since factory chambers are typically cleared more like .008 to .012 or so... Your fired cases expand a lot when fired and need to be reduced a lot to hold the next bullet. These cases will work harden quickly and work hardening increases spring back, so you need to resize smaller and smaller after every firing to get the same neck tension.

Also when reducing the neck diameter by more than .010 per resize you open the window to run out. It would be far more difficult, if not statistically impossible to reliably maintain .001 run out when resizing the neck by more than .010".

So as mentioned above the OP appears to be reducing the case neck diameter more than the minimum required and therefore maximizing the introduction of run out.

So in conclusion, with a factory chamber, use thick neck brass to minimize neck expansion when fired, and resize the neck no more than you need to get the case to hold your next round.

Now I will throw in one further tidbit to chew on and that is the introduction of taper to the case neck when doing heavy resizing. When reducing the diameter by .010 in one resize the neck will be smaller at the opening than it is toward the shoulder. The solution is a two step resize. Resize by -.009 and you will have some taper, then resize a second time at -.010 and then you'll take out the taper. You may also find that the neck opening is actually larger after the second pass at -.010 than it was after the first pass of -.009. At the very least you will find that you will have less overall neck tension on the two step resize than the single step resize to -.010.

Anyway I hope that makes sense.
 
Well fellas I think I've got this issue beat for the time being. I picked up a .336 bushing (.002) tension and a light clean up with the neck turner and I'm seeing less then .002" run out with most around the 0.001". I definitely was resizing more then .010 actually .015 give or take so It makes sense now that I would be experiencing the run out as I was. Thanks for all the great info, gents, I definitely have a ways to go in achieving my reloading goals but feel that much closer tonight. winning!!
 
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