@ 07:25 am (GMT)
Nathan FosterHi Francis, no worries.
Both the 7 and 8x57 rifle chambers can at times be somewhat oversized at the neck, especially old military chambers.
If you skim the shell holder or try to use extra force, it will make matters worse and you will likely ruin the die (the threaded cap section).
To remedy this situation, you need to sand the mandrel as shown in the Reloading book. The mandel I was sanding in the book was actually an 8x57, same issue.
You may also like to order a second spare mandrel now, just to give you some piece of mind (in case of mistakes). Some reloading suppliers keep spare mandrels in stock. Alternatively, you can order an undersized mandrel from Lee. This will be .002" smaller than your current. This may or may not be narrow enough. You will just have to see how you get on.
Try not to over do it. If you go too tight, it will create poor concentricity when seating bullets. If your first 18 were fitting OK, I would suggest that you may only need to drop down .002" to get a tight neck with all cases.
Hope that helps.