Throat Realtion

[Wolfdog91]

Anyone mind explaining why having a bullet sized to fit the throat of the chamber is more important then having it fit the rifling ? Always thought having it fit the rifling was the most important

[Winger Ed.]

It will be aligned & compress as it leaves the case, and fit/seal the bore better.

If it's too small, it may or may not obturate(squish/compress) enough and you can get some 'blow by',
lose speed, and maybe get some gas cutting on the boolit. Sometimes that will cause leading.
If it's on the larger side, the first 1/8th inch of the bore will make it right and give a perfect fit.

[Tar Heel]

At shot-start, when that case neck opens up, the bullet is no longer supported. You do not want it canting and entering the tube at an offset angle. It's one of those minor details which when taken as a community, affect precision of the shot.

In the world of precision rifles, half a thou is like the grand canyon. A whole thou is like the Marianas Trench.

[country gent]

When a cast bullet is fired it compresses and swells. Unsupported it may not swell evenly and stay straight but when supported in the throat it stays square and expands evenly and accurately

[reddog81]

The throat should be the same size or a smidgen larger than the rifling. If the bullet fits the throat it will fit the rifling. If the bullet fits the rifling it might be smaller than the throat.

How much does this matter? It depends on what type of gun / cartridge we are talking about.

[JWFilips]

I shoot a lot of Mil Surp rifles. The throats are always worn! The only way to make them shoot well is to use a cast bullet that is sized for the throat!
I have a beautiful JP Saure & Son 8 mm Mauser 98 It Needs a .338 bullet to shoot good groups.
Fit the throat and it will go down the bore fine and will improve accuracy.
Now if the chamber dimensions will not allow a "fat bullet" to chamber in the case ...you need to neck turn the brass! Usually .009" thick is the magic number

[DougGuy]

Two things..

First, a revolver's dimensions need to read much like a common kitchen funnel, larger diameters in the back, getting progressively smaller toward the muzzle. This way, the boolit stays tight as it travels from case mouth to muzzle.

Second, in a perfect world a revolver's boolit is sized .001" to .002" greater than the groove diameter of the barrel. (This insures there is enough excess so that the boolit is swaged into the rifling and makes a good seal. A boolit sized the same as groove diameter may or may not seal well in to the rifling). The cylinder throats should be sized .0005" to .001" greater than boolit diameter, this insures the boolit is presented to the forcing cone sized as it was loaded, OR obturated to throat diameter.

The cylinder will serve as nothing more than a multi-port sizing die when throats are too small.