Expanding with a mandrel

[jsthntn247]

I didn't want to hijack the other thread so I'll ask on another one. Do most of you use a bushing die to size necks down before running through the mandrel does the unsized portion not touched by the mandrel effect anything? How far do you size down under mandrel size and does going too far undersized seem to induce runnout?

 

[Lapua40X]

My turned necks are sized in the Redding bushing die .001 under my mandrel size. I run the mandrel the full length of the neck. I rarely find runout above .0005 but excessive runout in my shop is more commonly attributed to lack of care in seating than any other factor.

 

[Joe R]

I run the mandrel the full length of the neck.

+1

 

[snakepit]

My turned necks are sized in the Redding bushing die .001 under my mandrel size. I run the mandrel the full length of the neck.

+1 I follow this same procedure except mine are no turn necks.

 

[jsthntn247]

Just got these in to play around with neck tension. I finished loading 150 rounds for a match. The only mandrel I had gave neck tension less than .001. It was just enough to grip the bullet where it would not spin in the neck. However 12 of the 150 would not grip the bullet and would allow it to spin in the neck. What would make these cases different from the other 150 when the same prep was done and the same mandrel was run through the necks? All cases were tubmled, deprimed with bushing neck sizing die reducing neck diameter 1/2 of intended, ultra sonic cleaned, dried, annealed, graphite added to necks, bushing f/l die to bump shoulders and size necks .001 under mandrel diameter, trimmed, expanded, loaded.

 

[Joe R]

jsthntn247 said: What would make these cases different from the other 150 when the same prep was done and the same mandrel was run through the necks?

First off, I agree with everything that Donovan said.

I am also looking to improve neck tension consistency and I would also suggest that you consider dwell time when resizing the brass, both with the die and the expanding mandrel. I am now stopping for five seconds before lowering the ram. Just a thought....

Kindest regards,

Joe

 

[jsthntn247]

My input is, you do not have to run your brass over a mandrel after sizing the neck with a bushing.....
Not saying no body does, but very few that I am aware of do. Most just size with a desired bushing and seat the bullets.

The reason why you were getting inconsistent grip to some cases could be several reasons.
I suspect one of three reasons:
1 - inconsistent neck wall thickness
2 - inconsistent neck turned (heat being a culprit when turning)
3 - brass is not on the same cycle
I suggest to do a slight neck-turning clean up of ALL the brass, of say a 1/2-thousandths or less.
My 2-cents
Donovan

I was thinking the same thing and re-turned the brass taking .0002 off per side before loading these, I took about .001 off on the first turning. I went very slow on the turning this time making sure not to get the mandrel even the slightest bit warm. They have all been 2x fired. I am having to use the mandrel because I couldn't get consistent seating pressure using the bushing alone. Using a hydro bullet seater the seating forces were all over the place.