Redding 'carbide' expander ball too small? Bullet is bulging the case

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Marcos

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Hello,

I am new to reloading and currently working on a 308 load development. My first batch of 20 rounds was reloaded and shot without issue. I used unfired Lapua brass, Lapua scenar L 175 gr (got them for a good price in 1000 unit bulk), VV N550 between 43 and 46 grains. Velocities were slightly higher than expected, but no pressure signs, etc. I identified that between 44 and 44.8 gr the velocity curve is rather flat and am happy with the velocity.

Today, I reloaded a second batch, this time to experiment with various seating depth, again using unfired brass. I am missing a piece for my expander mandrel so haven't been able to use it yet. Therefore, my 2 choices to expand the case mouth on new brass are to use the expander on the neck die or the "carbide" expander ball on the FL die. I went with the "carbide" ball as is supposedly glides better on the brass.

Unfortunately, when came time to seat the bullet: CASTASTROPHE, the mouth was totally deformed/bulged by the bullet. Just to make sure, I recreated the problem with another unfired Lapua brass, expanded with the ball and again a bullet would bulge it.

Long story short, the "regular" expander on the NK die is larger than the "carbide ball" by 2 thousands.

Is it possible that the Lapua brass is thicker and "springs back" excessively to original shape after passing the mouth in and out the "ball" as opposed to the other one? At least I have a working solution with the other expander and am confident that a quality mandrel won't cause this problem.

Just curious if others had similar issues before? Is it worth an email to Redding or something?

Many thanks!
 
Not doing the full resize on the unfired brass, just opening the case mouth using the ball/button from the die so the bullet can fit (otherwise it is impossible). I believe the carbide ball has a .306 diameter and the button was about 2 thousandth bigger, which seems to make a huge difference: bullet deforming the mouth and compressing the neck vs. seating with normal resistance and no brass deformation. Once I have the missing part for the expander mandrel I will do a test with it too.

I have a FL bushing die for resizing fired brass, but have not used it yet. I chose a .335 bushing (3 thousandth smaller than the OD when bullet is seated). I hope it will work!
 
Just thought of another (better) explanation; I had initially setup the micrometer seating die way up (the micrometer part), so maybe the case mouth ended up hitting inside the die during seating, thus crushing the neck downward in the case. The bullet seamed to fit in the mouth without much effort until the last part of ram travel (must have been resistance from the case being crushed).

"Learning every day" they say... Will still experiment with various expanders see what ID they give to new brass.

Marcos
 
Most expander balls that I have measured are .3062 to .3069 (measured with a micrometer), if yours is at least .306” then you have other issues.

I’ve seated many bullets into brand new Lapua brass and never had a problem.
 
You are encountering a phenomenon called buckling, due to excessive downward force. Normally, the expander ball does its work on the upward pass. If you are trying to establish the COAL to the lands, there are much easier ways to do it.
 
I corrected the issue by screwing-in the seating stem further and screwing-out the die body. It was a clearance issue between the case mount and the seating die. Thus far have loaded 60 new Lapua brass, expanded with carbide ball or regular button without issue. Contrary to my initial post, it was not changing the ball/button that solved the issue as I had also played with the seater in the meantime (forgot at time of posting…).

Thanks everyone!
 
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