pressure ring ?

[garyw]

whilst trying to expand my knowledge of all things relating to reloading i keep reading about the pressure ring on bullets.can you guys offer an explanation on this and where would i find it in various calibre bullets.
thanks garyw

 

[Kodiak99317]

The pressure ring exists on flat base bullets only, at the base.

 

[Twud]

Do all bullets have a ring, or only match bullets? Why only flat base? Never could understand how you can push a 2438 bullet down a 243 bore.

 

[Preacher]

Twud-
a 243 bullet in a 243 hole will fall right through, a 243.8 will have really nice grooves in it from the rifling, and thats the best I can come up with ........

 

[BoydAllen]

Typically, a pressure ring,a slightly larger diameter adjacent to the base of a flat base bullet) is present on match bullets that are of the custom hand made variety. I have been told that production bullets have their pressure rings "ironed out" in order to facilitate their use in automatic loading machinery.

As to comments about bore diameter, that is the diameter of the circle that includes the tops of the lands. It is the groove diameter that determines bullet fit. For example a .30 caliber bore will typically have a .308 groove diameter, a good match for bullets of the same diameter. Many times there are small differences in bullet and groove diameter. This does not pose a problem because the gilding metal jacket,mostly copper) and the lead core are sufficiently malleable to be deformed to the dimensions of the barrel, particularly when you consider the 50-60,000 PSI pressure that is driving the bullet.

In a 6mm barrel it is the groove diameter that is .243. Depending on the height of the lands of a particular barrel, the bore diameter will usually be somewhere in the range of .236-.237.