6x47 Lapua neck tension issues

[distantfoe]

Having some issues with more neck tension than I want when sizing newly form 6x47 brass with a .268 bushing. Loaded ammo measures .270 and the bushing takes brass all the way down to .266. (No expander button involved)

I'm going to guess I need a .269 or .270 bushing? Ideas??

 

[alf]

It's been noted before that you can't always trust whats stamped on the top. So unless you have a set of pin gauges to measure the bushing you have, order several to cover all your bases.

In the mean time, radius and polish the upper portion of the expander ball, and use it. You might be surprised.....

 

[mikecr]

What do your unloaded fired necks measure?
Resultant bushing sizing changes from stamped with >5thou sizing. This situation is not a bushing 'problem', but a result problem to expect and plan for.

You should also plan to pre-expand necks with hardened expansion, instead of soft bullets (which make terrible expanders).

 

[distantfoe]

Rifle is at the gunsmith for a new barrel. It wore at 6.5x47 barrel, switching to 6x47 so I'm not sure of the neck dimensions but it should be a "no-turn neck."

Since the current bushing set up yields .003 tension, you're saying I should use a expander to slightly over size then try resizing the brass to simulate fired brass?

 

[mikecr]

A .268 bushing wouldn't put .270 necks down to .266.
This combo should take a neck to .268 with outward springback leaving it at ~.269. This is about all the actual tension that matters. Any more undersize is just more interference fit to seating, which provides no function other than to vary your seating depths.
Pre-expansion drives thickness variance outward -away from bullet seating. It also biases the stored energy inward(direction of last springback), rather than outward(something that comes into play when ammo is not immediately used).
Best expansion runout-wise is with a Sinclair expander system(merchandised for neck turning).

What size are the necks before sizing with the .268 bushing?
How did the necks get from 6.5mm to 6mm?

 

[distantfoe]

I sized from 6.5 to ~.274 with a bushing die with the bushing removed. Then sized with a .268 bushing in place which resulted in .266 without the expander and almost .267 with expander ball in place.

Just tried a Sinclair expander (.241"), it brought necks to .268.

 

[Jeff Conover]

Annealing is critical to controlling neck tension. using a .266 bushing and a .270 my seating pressure will run 32-36 LBS. Fire case and on next loading pressure creeps up to 55 LBS range. Anneal necks for 4.2 seconds and seating pressure is back in the 30's. For 600 benchrest most guy anneal after every firing.

 

[Scott Harris]

A .268 bushing wouldn't put .270 necks down to .266.
This combo should take a neck to .268 with outward springback leaving it at ~.269. This is about all the actual tension that matters. Any more undersize is just more interference fit to seating, which provides no function other than to vary your seating depths.
Pre-expansion drives thickness variance outward -away from bullet seating. It also biases the stored energy inward(direction of last springback), rather than outward(something that comes into play when ammo is not immediately used).
Best expansion runout-wise is with a Sinclair expander system(merchandised for neck turning).

What size are the necks before sizing with the .268 bushing?
How did the necks get from 6.5mm to 6mm?

+1

I recommend using the Sinclair Gen II Expander die with a carbide turning mandrel to ensure more consistent neck tension. If you want less neck tension, use an expanding mandrels and PMT sells carbide versions which are a LOT better than regular steel ones.

 

[stroked96s10]

No neck turn would put you at .272 i believe. My barrel is .267 and i'm using a .264 redding bushing in one of my smith's dies. I haven't checked loaded/unloaded unfortunately, but it works. There's enough tension there to hold the bullet still that i can't pull it out.

 

[SecondsCount]

I had the same issue: Link to Post

I ended up neck turning .001" off the parent case and using a .269 bushing.

 

[distantfoe]

I thought about neck turning, just too much brass to mess with.

I ended up necking brass back up to .257 and necking down in smaller increments. The .269 bushing produced .2685 necks so seems like it's gonna work.