When do you use an expander mandrel?

[Chaotik]

I am hoping that by using an expander mandrel I am reducing run-out and getting more consistent neck tension.

So I have some questions for the experts on this forum:

When do you use an expander mandrel?
- do you use on new brass only?
- do you use it every time you load the brass?
- do you use it only once before neck turning fireformed brass?
- do you use it before or after neck sizing?

And, while we're at it:
When do you neck turn brass?
- do you neck turn only new brass or after it is fireformed?
- is this just done once in the life of the brass or is it repeated, and if so, how often?

Thanks in advance for your help!

 

[DennisH]

Their's two different types, or sizes. I use one to make sure all my necks are uniform. I would really have to pull out my notes to be exact on this question as I want a certain tension on my bullets when reloading. I have been using them for years, I have them all set up, just don't remember why I have it set up the way I do. I will have to dig into it to give an answer.

 

[hdbiker1]

When I open up a new box of Lapua, I always use an expander. Lapua necks always seem pretty tight when new, and some have small dents in the neck. I also use one before neck turning.

 

[searcher]

First off - I don't hold myself out to be an expert. That said, expander mandrels are of great use in shaping your necks so that they will fit onto your turning mandrel without (when all is working well) any slop between the mandrel and your necks. This "friction fit" greatly aids in evenly cut necks. The idea is to start with necks sized smaller than the diameter of your turning mandrel, then running them through the expander which opens them up to the desired size for a good fit on the mandrel. Most people cut their necks one time when brass is new and is, of course, a requirement to do this before firing when using a tight-neck chamber. I have turned necks on brass that has been fired multiple times in no-turn necks and it is best done after annealing as the necks tend to harden after multiple firings and can make turning a bit more difficult - or at least to take off a lot in one pass of the cutter. Once the necks are turned, it can be a one-time procedure on your brass - but I have also found that going over them again when half way through the life of the brass has proven worthwhile for me. you would think that brass will stay the same once cut to the same thickness - but it can become slightly off over time in my experience. As a rule though for most folks -it is a one-shot deal for that set of brass. Personally, I don't use the expanding mandrels for much more than when neck turning or perhaps making a dummy case for the Hornady tools.

 

[Dave Berg]

You use it with new brass just to open the neck up to a reasonable diameter and to avoid the curled lip that you'll find on some cases. Then chamfer the inside of the neck a little. If you run a 0.2430" expander in a 6BR case then seat a bullet you'll still have plenty of neck tension.

It would be great to neck turn after fire-forming and trimming but with tight neck chambers that's inconvenient. Most do it on virgin brass which will usually have significant run-out and the amount you cut into the shoulder won't be uniform. I take the lazy way out now and call Ron Hoehn but check the last paragraph anyway.

There was a school of though ten or so years ago that said the way to get the most concentric rounds with very consistent neck tension was to size the neck slightly smaller than normal then run an expander in to push the irregularities to the outside. This wisdom came from the IBS 1,000 yard shooter of the year the previous year. Ken Markel, founder of K&M, made a set of expanders for me in two ten-thousandths increments for both 6mm and 6.5. Five expanders in each set with the middle one measuring what I thought the ideal neck ID would be. I tried them for about a year. Bullet run-out was reduced a little, at least enough that I could measure the difference which is a couple ten thousandths at the point the rifling starts to engrave the bullet. I used Ken's arbor press with the force measurement gauge and really didn't see any difference in seating force variance (one round to the next) vs. normal bushing die sizing. I didn't shoot any better or worse doing it that way and it added an extra step so I had a bunch of extra expanders that never got used again. I would guess there are folks who still do it that way.

Once brass is turned it stays turned but... I used to turn it a couple ten thousandths thicker than what I wanted then turn the last little bit off after the cases had been fired once or twice and trimmed to the same length (my K&M neck turners index off the case mouth so the trimming is kind'a important). Don't know if that helped either so now I just call Ron.

 

[SWRichmond]

Every time.

 

[amlevin]

When I open up a new box of Lapua, I always use an expander. Lapua necks always seem pretty tight when new, and some have small dents in the neck. I also use one before neck turning.

I too use a mandrel to straighten the necks on new Lapua brass. I also find that it can use a little more chamfer to ease bullet seating.

 

[Barlow]

I use them to vary neck tension, and push bumps to the OD. Barlow

 

[mikecr]

I use them for turning of course, and I only turn new brass.
I use them to neck up brass a cal or two as needed.
I use them always after neck sizing. This, with expander against a load cell to measure pre-seating forces.