24hourcampfire: I want to measure case necks, need advice.
Originally Posted by Winchester 69
I've recently seen a thread, probably on another forum, that shows a tandem inside reaming/outside turning process, I believe using Forster equipment. Using their handheld tool, a reamer replaces the mandrel, and the neck is turned normally. I don't see anything about it in their catalog, but you might inquire at Forster to confirm/obtain info.
.021" neck thickness is very thick indeed. I turn a lot of necks and before your posting the thickest I had seen was on my 6.5 rem mag brass which is Remington and varies from .015" to .017". With a .292" neck on my rifle I have to turn down to .0125", the math is .292"-.264"=.028"-.003" (recommended clearance)=.025"/2=.0125". In turning from .015"-.017" down to .0125" I had to do it in 2 stages cause the case can not be gripped hard enough to keep it from spinning when trying to turn too much brass off at one time. You will have your work cut out for you going from .021" down to your target of .016".
I have the Forster hand turner
which I like because it has a wide blade and makes a smooth cut
In regards to your question, Forster makes a reamer also that will fit in the hand turner
shown here next to the hand turner mandrel
The Forster reamer is .0025" to .003" larger than the caliber diameter. This enables you to inside ream a fired/unsized case if you have set your brass up for the .003" recommended case neck clearance. You can attach it and ream the inside of the case at the same time as you touch up the outside of the case
I say "touch up" because you can not ream the inside until you have fired the case and created the .003" inside neck clearance which means you have already turned the new cases to create this condition. Trapping the neck brass between the outside turner and the inside neck reamer makes for a very consistant neck thickness. It is also useful to remove do-nuts completely back to the level of the rest of the inside neck brass.
The K & M is an excellent tool but it is more expensive, more complicated and has a narrower blade. They have a cutting mandrel (also expensive) which will remove any do-nut that protrudes into the sized case neck. This mandrel has the cutter on the end and because of the springback in the brass I did not find this as consistant as the Forster since the Forster has a blade that covers the entire neck at the same time.
As someone has said, in your case you would need to ask for a .259" neck if you want your brass to have a neck thickness of .016", the math is .224"+.003"= .227"+2*.016"=.259". Gunsmiths very seldom hit that number exactly, IME, but even so you would be able to adjust for the .003" neck clearance by varying the thickness you turn the necks to.