chamber and die dimentions

[Bart B.]

The unsized (neck) part centers the round in the factory chamber.

If the bushing sizes all of the neck that it can, accuracy is not as good.

I disagree. See post #19.

The only way a case neck can center in the chamber neck is to have matching diameters of the chamber neck. That doesn't happen.

Measure both to the nearest .0001" and you'll see why.

 

[gunsandgunsmithing]

I disagree. See post #19.

The only way a case neck can center in the chamber neck is to have matching diameters of the chamber neck. That doesn't happen.

Measure both to the nearest .0001" and you'll see why.

Are you saying than the unsized portion never contacts the chamber?
Here's a pic of a cross sectioned 222 barrel stub with a bunch of rounds. It's not pretty and wasn't intended to impress anyone but it clearly shows where the bushing die sizes and where it doesn't, at the bottom of the neck. It looks like there is a sharp edge there but it's just the glare from the flash, but the wear is evident with the naked eye. That barrel shot very well for a long time for him.

 

[Bart B.]

Are you saying than the unsized portion never contacts the chamber?

...sharp edge there but it's just the glare from the flash, but the wear is evident with the naked eye.

Yes. Not while the bullet is being pushed out of the neck.

If a 30 caliber bullet needs 15 pounds of force to push it out of the case neck (typical for some match rifles), at about 200 psi in the case, the bullet starts out. That won't expand the case neck to a larger diameter.

Same force needed for a 26 caliber bullet to move, about 280 psi needed in the case.

It's possible that some case points where the neck meets the shoulder may have caused that shiny spot touching the chamber at that point. Precise measurements of cases and chambers will verify. As will a squeaky clean sized case with layout dye around that point then pushed into the chamber; if it wipes off, it is touching.

And there's the possibility the case rubbed that part when it was chambered as the case was resting on the bottom of the chamber but slid up and centered being pushed into the chamber shoulder by one of the external forces.

 

[mrjdasr]

Yes. Not while the bullet is being pushed out of the neck.

If a 30 caliber bullet needs 15 pounds of force to push it out of the case neck (typical for some match rifles), at about 200 psi in the case, the bullet starts out. That won't expand the case neck to a larger diameter.

Same force needed for a 26 caliber bullet to move, about 280 psi needed in the case.

 

[gunsandgunsmithing]

Yes. Not while the bullet is being pushed out of the neck.

If a 30 caliber bullet needs 15 pounds of force to push it out of the case neck (typical for some match rifles), at about 200 psi in the case, the bullet starts out. That won't expand the case neck to a larger diameter.

Same force needed for a 26 caliber bullet to move, about 280 psi needed in the case.

I suspect it's more than that, particularly if seated into the lands and I believe it will depend some on neck thickness and tension.
As far as neck tension alone goes, lots of BR shooters use very little at all. You can move it with your fingers. I prefer more but some don't

 

[mrjdasr]

hooray, solved my problem dug out a redding bushing full length die i havent used in 20 years
stuck it in the lathe, opened the hole in the bushing shelf up to .300 put in a .288 bushing and wallah
sized 3/4 of the neck and got the .454 dia shoulder
must be that die was made before we got lawyerized

 

[fguffey]

try to keep this generic and not step on toes

As Bart B. has implied; "It can not be done nor can it be understood" I am hoping you do not plan on making a full length sizing die and with a chamber reamer; same thing, according to the experts on this forum, "It can not be done and it can not be understood. To find that information a reloader has to go back to a time before the beginning of the Internet.

And then there is the rational.

F. Guffey

 

[fguffey]

The only way a case neck can center in the chamber neck is to have matching diameters of the chamber neck. That doesn't happen.

That is not true; a reloader could choose to neck size; meaning the case fits the chamber. And then; the reloader could partially sized the neck. The un-sized part of the neck would center. and then there is the other excuse for the case not centering; Seems there is always something wrong with the extractor shoving on the rear of the case etc. etc.

I am the fan of having nothing between the case body and chamber but air, when it comes to air I do not want a lot of it but the air I have between the case and chamber must be clean. So I suggest reloaders learn to control the amount of air between the case body and chamber; and that is the question the OP asked when he started this thread.

According to Bart B. that creates another problem with the fit between the chamber and case, Bart has claimed the firing pin shortens the case .005" when the firing pin strikes the primer.

F. Guffey

 

[243winxb]

All this does not matter if you fire for score on the wrong target. You know who you are.

 

[fguffey]

All this does not matter if you fire for score on the wrong target. You know who you are.

And I am the only one that remembers you claiming the firing pin strike shortens the case .005" between the shoulder/case body juncture and case head before the primer ignites the powder; reloaders that are able to keep up should be asking all kinds of questions.

F. Guffey

 

[hogpatrol]

Now you've done it!

 

[Bart B.]

And I am the only one that remembers you claiming the firing pin strike shortens the case 5" between the shoulder/case body juncture and case head before the primer ignites the powder;

No. I, too, remember, but it was 5 thousandths of an inch. Not 5 inches.

Why else would a 308 Win dud primed case with headspace .001" shorter than that of chamber have .005" less after the firing pin that primer? Or the same amount less from a 15% reduced powder charge, bullet and live primer?

What was the other reason H&H put a belt on rimless small shoulder angle magnum cases?

Hatcher mentions .007" 30-06 shoulder setback before firing in his book.