I am trying to understand how much difference is appropriate between the outside diameter of the neck of a loaded round vs the neck diamater of your chamber.

I.E. if your chamber's neck is .307 and the diameter of a loaded round with your preferred components is .3045 is that enough difference or 'release'?

I know there should be some minimum difference, I am just trying to learn what it should be.

.0025 is enough. The smallest benchrest shooters go is .0015" with outside neck turned brass.This can be very dangerous if you dont know the exact diameter of your chamber. For factory chambers look up the maximum neck diameter of a loaded round here. http://www.stevespages.com/page8d.htm The loaded rounds neck diameter should not be larger than this for a factory gun. To get an idea of your chambers neck diameter of a factory gun, measure a fired cases neck diameter, then add .001" for brass spring back.

Yes, that is enough difference for bullet release. I think .002" is a minimum for bullet release.

Just curious why you would need .002 for proper bullet release??

Seems like the info about benchresters is useable.

I guess I could see .002" is a good idea for your basic factory hunting rifle as far as loading lots of wierd factory and reloaded ammo with varying brass manufacturers.....but certainly not necessary if brass dimensions are known and kept to tolerance?

Hmmm... I think I'm figuring it out, but in short, I have a rifle with a neck that is .307 and the ammo I want to shoot in it is to the best of my ability to measure, .3045
If this is marginal, I will go to a different brass, I have some Winchester brass that is thinner in the neck, and a loaded round with it measures .303 to .3035. I prefer the brass with the slightly thicker necks....

3 things to keep in mind. 1. Your difference of.0025" is not the true clearance on each side of the loaded rounds neck as it sits in the chamber. 1/2 of .0025" or .00125" is your real clearance. 2. When you measure a loaded rounds neck diameter, makes sure the measurement is taken over the "pressure ring". The pressure ring is found on some match grade custom bullets. Berger is one. It is loacated near the base of the bullet. This ring is from .0003" to .0008" larger than the bearing surface of the bullet your using. When outside neck turning for custom tight necked chambers for benchrest, this must be considered. 3.Some have loaded ammo with 0 neck clearance, the spring back of the brass holds the bullet for the next loading. This is for the very expert shooters like Varmint Al. Varmint Al's Website

quote:

Originally posted by Fish30114:
Hmmm... I think I'm figuring it out, but in short, I have a rifle with a neck that is .307 and the ammo I want to shoot in it is to the best of my ability to measure, .3045
If this is marginal, I will go to a different brass, I have some Winchester brass that is thinner in the neck, and a loaded round with it measures .303 to .3035. I prefer the brass with the slightly thicker necks....

You are OK with a difference of .0025" Nothing to worry about there.This is very close to factory ammo and chambers. Remember the factory ammo and brass most times will not be at the maximum neck diameter that is in the drawings at Steves website. Your loaded rounds will all most always be smaller in diameter than what is shown in the drawings. For 243 win, i am very happy when a loaded rounds neck measures .276" the maximum for the caliber.

quote:

I.E. if your chamber's neck is .307 and the diameter of a loaded round with your preferred components is .3045 is that enough difference or 'release'?

Yes.

Yes, my .002"(.001" per side)suggestion is a guideline for a factory rifle using standard factory brass. If you have a known custom tight neck chamber and outside neck turn brass you can set the cleareance at what your rifle likes.

A country boy way to avoid all of the measuring (unless you're into that stuff) is to take your fired case and a bullet. If the bullet will slide reasonably, easily butt first into the case, you have enough chamber clearance.
As you fire your brass, metal migrates forward and the brass gets longer. This is why you measure your brass and occassionally have to trim it. But the necks also grow thicker and after a period of time, there isn't enough room for it to properly release the bullet and pressure is climbing and you're getting thin spots in your case.

OK guys, I think I'm feeling better about this, my smith will be looking at this rifle for a couple of other issues, so I'll check on his opinion too...

wasbeeman, I want to make sure before I fire this rig

Buliwyf, I don't have a pre-determined goal, I just know what the neck on this rifle is, and I want to be sure that the differential between the cartridge with my preferred components and the neck is good! I don't think I would want a hunting rifle with any tighter tolerance than this, I don't intend to shoot anything but my custom loads in it, so shooting some loads I don't know the loaded neck diameter on isn't my intent....I just want to make sure I am not in a dangerous zone with the components I intend to use.

Thanks a lot guys--Don