I'm loading up some new 6BR Lapua brass for initial testing in a Savage LRPV. Based on advice from the 6BR site I ordered an expander ball for my Forster Bump Bushing resizing die, to open up the Lapua unprimed brass.
Only measured 11 cases but the neck OD before using the expander ball averaged 0.2672", with a standard deviation of 0.00013". After expansion, average and standard deviation increased respectively to 0.2683" and 0.00016". So, yes they were a little tight.
After loading with Berger 80 grain Varmint bullets, the OD increased to 0.2692". So, it looks like I have about 0.001" of tension. Standard deviation significantly reduced to 0.00007". I'm thinking the bullet has a mandrel effect and reduced the ovality of the neck without a bullet.
So my question would be, whether I should continue to use this expander ball in resizing the fired cases? Have not shot any yet. I plan to use the .267 bushing, so I'm thinking resized cases without the expander should be about 0.268 after springback. So the expander ball may open them up another 0.0003", or essentially very little. Do you see any harm or benefit in doing that?
It seems to me that the ID of the neck is a more critical dimension than the OD. The use of the expander ball would seem to offer a way to make this ID more uniform. The extra working of the brass, compared to bringing it down from .271 or so to .267, would seem trivial.
Only measured 11 cases but the neck OD before using the expander ball averaged 0.2672", with a standard deviation of 0.00013". After expansion, average and standard deviation increased respectively to 0.2683" and 0.00016". So, yes they were a little tight.
After loading with Berger 80 grain Varmint bullets, the OD increased to 0.2692". So, it looks like I have about 0.001" of tension. Standard deviation significantly reduced to 0.00007". I'm thinking the bullet has a mandrel effect and reduced the ovality of the neck without a bullet.
So my question would be, whether I should continue to use this expander ball in resizing the fired cases? Have not shot any yet. I plan to use the .267 bushing, so I'm thinking resized cases without the expander should be about 0.268 after springback. So the expander ball may open them up another 0.0003", or essentially very little. Do you see any harm or benefit in doing that?
It seems to me that the ID of the neck is a more critical dimension than the OD. The use of the expander ball would seem to offer a way to make this ID more uniform. The extra working of the brass, compared to bringing it down from .271 or so to .267, would seem trivial.