How much "room" does the neck of loaded round need to prevent a pressure spike from the brass not being able to expand enough to release the bullet?

For you guys with "tight neck" chambers, what is the difference between the measurement of your loaded round and the chamber itself (at the neck of course)?

Thanks!

Roger

.002" difference favoring the throat will keep you out of trouble. I've read of some using .001" or even a hair less, but your "pay close attention" index goes up very quickly as the dimension shrinks. Some release is required but I'm not certain what the absolute minimum would be.

rogerinneb,

My benchrest rifles have .262 necks in chambers cut with precision reamers. I turn my case necks to .0089. The bullets that I shoot mic. at .2432 to .2433. The loaded round mics about .261 All that adds up to a clearance of around a half a thousanth. Keep in mind that even temp (expansion and contraction) can change things quickly here. Everything in the rifle is straight and square. It took me quite a while to arrive at this dimension. And for those of you who say that no one can measure that close I agree. These cases are cleaned meticulously inside and outside on the necks when loading them. I spent a lot of time in trial and error changing the neck turner just a tiny bit at a time. I would recommend that you give yourself at least .002 or more of neck clearance. I would not hunt with or use ammunition with this tight clearance for any use but target shooting.
You asked about tight neck clearance and I told you what works in my rifles. But it takes a lot of thought,experience, and caution to make it work safely and correctly.

knobmtn