Brass problem in neck area.

[jkehley]

Hi members, has anyone ever had this problem. Started with new unfired Federal 300rum brass, full length sized without expander ball. Next I expanded with a K&M expander then trimmed all to the same overall length, then cleaned up neck thickness with K&M neck turner just to remove thick areas. Then I proceeded to neck size and load and shoot. All went well until after the cases were fired and neck sized for the second loading.
This is where the problem came into play. I cleaned the cases and neck sized as usual but the necks are flairing out about .010 in diameter at the very edge of the mouth for a length of aprox .040 to .050. The remainder of the neck length has retained its sized diameter, it is only on the very end of the mouth that is flairing.
Any ideas on a fix? Annealing???

 

[ddgo]

neck turning

Is this a factory chamber? And how much did you turn the necks? ddgo

 

[jkehley]

Yes it is a factory chamber. My finished thickness is .0125. I just clean up the thick spots to try to obtain a consistent neck tension.

 

[P KUNDA]

In the future-Anneal the necks before sizing

Peter

 

[jkehley]

I have also taken a closer look at the fired unsized brass and the mouth is tapered in, as if a crimp die was used. The effects are very noticeable to the naked eye.

 

[Black Diamond 408]

Brass is too long or the chamber neck area is too short. This will cause pressure spikes.

 

[Quarter Round]

Started with new unfired Federal 300rum brass,
full length sized without expander ball.
Next I expanded with a K&M expander
then trimmed all to the same overall length,
then cleaned up neck thickness with K&M neck turner just to remove thick areas.
Then I proceeded to neck size

Any ideas on a fix? Annealing???

Your problem might have occurred during the length trimming step. Try trimming your next batch of new brass after the last neck sizing. If you used a trimmer with a piliot you probably expanded the brass neck at the very end more than the K&M expander and this resulted in thinner brass at the mouth of the neck.