SmallCaliberCentral

I am just beginning to do some neck turning with my recently purchased Forster equipment.

Just curious as to how "snug" the case neck should fit onto the mandrel.

Most of my FL resized cases take a fair bit of effort to slide them onto the mandrel, and I can feel the resistance when turning even with a bit of oil or sizing wax to aid it.
To make it easier I extended my expander button in my resizing die to the very bottom and then run the case neck over this once or twice and it makes it easily slide on the mandrel.

As long as there is no play or slop that I can feel am I okay?? Or should the neck be tight on the mandrel use a bit of lubricant to assist it?

Is your barrel a custom chamber?

Is this new or fired brass?

If fired brass, you will need to clean the necks before sizing.

If new brass, you will need to size at least the necks.

Brass has been FL re sized, annealed, trimmed to length, primer pocket uniformed, and flash hole deburred.

The brass I am working with will probably not be neck turned. I have yet to check neck thicknesses on the majority of my brass but the ones I am testing the neck turning on (discards with dented shoulders and the like) are relatively consistent at around .012"-.013", so it is not likely to make a difference in my SAAMI chamber.

I just am trying to get the proper technique mastered so that if/when I get some brass that would benefit from this treatment I will be ready for it.

Some of my tests have turned out pretty good with about 70-80% cleanup and reducing it to a consistent .0115 thickness but I don't want to go below .012", especially in my SAAMI spec chamber.

I just am not sure if the neck should be fairly snug on the mandrel or just enough that there is no play.

New or fired brass?

I am assuming fired brass if you are FL sizing them.

Should be just enough clearance to let the mandrel turn freely. Otherwise, you end up with a sticky spot on every piece of brass where the cutter stops...and this leads to split necks soon.

Did you inside neck chamfer yet? If not, do that and try again.

Another problem to watch for if you've spun a few tight fitting necks on the mandrel is galling.
I had quite a bit of trouble with that on my Forester. I cleaned it up in a drill press with some steel wool.

Running just the expander ball through the neck will loosen them up a little as you said. You'll now have a different neck tension than you will get normally later on.
Resizing after turning again should be in order. Use whichever die you intend to use for this FL or neck.

Eventually I spun the mandrel in the press with some 400 grit paper and polished slightly with steel wool to get a snug fit but no galling.

Another problem to watch for if you've spun a few tight fitting necks on the mandrel is galling

This is actually what I was concerned with. While it hasn't happened yet I thought that it could happen so that is why I run the expander ball through it before placing on the mandrel.

Did you inside neck chamfer yet?

Yes I did that, this brass is all prepped and ready for loading. Some of the brass may have been previously reloaded 5-6 times others only once, I annealed them all so that they are closer in consistency than they would otherwise be.

I just received 200 once fired brass that are from the same lot, so these are the ones that will get all possible case prep done to them. The plan is to just clean up the necks a bit, (maybe 50-75%) to gain any extra edge I can, these will be used for my goal of some 500 yard kills on Skippy this summer.

I recently had a similar problem and removed the expander from my die and compared its diameter to another expander from a similar die. I found a .001" difference in diameter and I switched to the larger expander. It worked for me and the mandrel now slides in snug but not forcibly tight. I also use "IOSSO case lube (licquid) only on the edge of the mouth of my cases before they enter the mandrel. I do this by pouring a tiny amount into a thimble size plastic cap and partially dipping the mouth into it prior to neck turning. This not only lubes the inside but the outside of the neck so the cutter as well as the mandrel have lubricant. Sinclair sells an expander mandrel to use in addition to their neck turner pilot but if you have a correct size expander you wont need to buy theirs. I personally prefer the Forster to the hand held neck turners. (IOSSO lube has no stickey residue and no offensive smell. It is WATER rinseable, biodegradable and non-flammable. It inhibits corrosion and rust.) The preceding was taken from the IOSSO label for your info. Available from Cabela's.

I found the use of lubricant made a difference. By running the case mouth over the expander in the dry condition I found about half of the trial cases slid easily over the mandrel, not sloppy but a bit looser than I wanted. But when I lightly lube (Imperial Sizing Wax) the expander ball I get a nice consistent snug fit. I am pretty happy with my results so far. The cutter adjustment is kinda a delicate on the Forster unit, but after plenty of trail and error, I have gotten a consistent 0.012" with about 25-50% of the neck being cleaned up.

I dunno if it will make a measurable difference in accuracy but I enjoy case prep on the cold winter days, I reminds me of springtime fun with skippy