Case Neck Runout!

[BoydAllen]

http://www.sinclairintl.com/.aspx/pid=33148/Product/Imperial_Application_Media

Just remember, dip. and twist before lubing the outside of the case. They also sell the lube to recharge the ceramic balls.

 

[25AI260]

very interesting post

 

[fdshuster]

phil3: You hit on the reason why many of us do not use the inside neck expander, when possible. I've opened a new box of factory dies, never used, looked at the underside of the sizer die & saw an off-center decapping rod. They are very easily bent, and all but impossible to straighten. Even at that, start out with one that is perfectly straight & run it into a case that has an off center primer flash hole (very common with some brands of brass), and in the blink of an eye, the rod is forever bent. My main use brass for the AR's is G.I. Lake City. New, first time loaded brass will have runout, even happens with my Lapua in 222 Rem., 223, 220 Russian, 6BR & 308. With the first firing all but a very few will straighten out nicely. Those few may require 2 or 3 firings to fully straighten, and on rare occassions I may get 1 or 2 that will never straighten, and I write those off as defective from the time the brass was formed. I'm using the Sinclair concentricity gauge to segregate the rounds according to runout severity and use them accordingly, keeping those at .002" and less for precision & longer distances.

 

[BoydAllen]

I just full length sized 50 new Winchester case, with a Redding FL die, floating carbide button in place. Results are not good. For Winchester brass, the cases did not look too bad (or great) averaging around .0015" neck wall thickness variation and .0035" neck runout, right out of the bag. After the resizing, virtually all cases had runout of at least .004", with some at a whopping.008". Is this just endemic to full length sizing dies, or is there something amiss with my procedure? Or, are bushing dies the only way to improve runout? Since it was stated above that bushing dies may not work in ARs, I wonder what AR users are doing to minimize runout.

Thanks.

- Phil

Just for grins, pull the expander mandrel out of your die and size a case, then measure the runout. After that, measure the diameter of that case (sized without the mandrel) and compare that measurement to one that was sized with the expander in place. FYI if you want to get less runout the answer is not to eliminate the expander, but rather to do it as a separate step, with a die and expanding mandrel, lubing the insides of the necks with some sort of oil and inserting the mandrel carefully, to minimize the axial force on the case neck. Years back I discovered this working with a one piece .22-250 FL die.

 

[markm87]

I went through this a while ago. Best thing i ever did was dump the expander ball. I still use the sizing die and then follow up with an RCBS neck expander to open the neck back up after the sizer squeezes it down.

This is much straighter and also reduces the trimming due to not PULLING the ball out on the up stroke.

Bushing dies were horrible for me. Donuts, runout, etc.