inside neck diameter of cases

[atr]

Call this a new "discovery" for me.....but I was measuring the button on the sizing dies which forms the inside neck diameter....

for 303 Brit (.311) measured was .309
for 30Cal (.308) measured was .306
for 7mm (.284) measured was .282
25 cal (.257) measured was .255

all were .002 under which is what is providing the friction fit of the bullet to the neck....

I thought it was interesting that dimensional difference was a uniform 0.002
It would make sense to me if we followed this pattern when we loaded cast rounds...

[beagle]

Yes, and you can bet that when you seat a cast bullet in it that that bullet is being sized down at the same time.

I found this out when I pulled some Ah Shi_t .30 Carbine loads one time. My bullets had shrunk during loading from .310" to between .308 and .309"./beagle

[405]

Yep,
Kind of a standard to be .002" under nominal bullet diameter. Most of this is a "one size fits all" thing. The problem with cast bullets especially those of softer alloy is that the .002" under sizer buttons and expanders WILL cause a reduction in the size of the bullet as it is seated as beagle stated. Of course this .002" is standard for Jbullet reloading and won't affect them. Also, that .002" under button after running through the neck.... the spring back in brass may leave the neck ID a full .003" under nominal bullet size.

Many of the BPCR shooters using soft alloys, in single shots only want enough neck tension to gently hold the bullet in place. Custom sized neck expander dies or custom sized re-sizing dies are used for a specific bullet diameter to prevent this unwanted bullet distortion or sizing during the seating process.

[runfiverun]

that .002 is a nice neck pressure for flgc's though.
now you know why the m-die is recommended so often. or an oversized button. for cast

[Boerrancher]

For many some of my black powder 45-70 loads I don't resize any portion of the neck. I compress the powder a bit with the boolit and hold it in place by a light taper crimp. Since my rifle is a single shot all the crimp has to do is keep the boolit against the powder until it is fired.

If you don't have a Lyman M die, a lee universal case expander die will work also. I use the Lee, because it is universal, but I think the M die will work better because it seems to be more caliber specific.

Best wishes from the Boer Ranch,

Joe

[joeb33050]

My M die shanks-below the beller swelling- measure:
.30 = .307"
7MM = .2815"
.45 = .4547"
This suggests that the M die doesn't expand the neck, since the M die shanks are about as big as the expander buttons.
Are my bullets being sized down?
joe b.

[pdawg_shooter]

I paper patch so I tend to reload unsized cases. The patched bullet is usually enough over sized to work. I neck turn all my bottle necked brass uniform. In my straight wall cases I size to the bare minimum.

[Bret4207]

This is part if the reason I tend to neck size, but no more than absolutely necessary. I have a few oversize buttons that work pretty well.

[Boerrancher]

since the M die shanks are about as big as the expander buttons.
Are my bullets being sized down?
joe b.

Depends on how work hardened your brass is. If the brass is hard enough it could possibly shrink the boolit some. Only way to find out is to pull a loaded one.


Best wishes from the Boer Ranch,

Joe

[atr]

thanks guys,,,
this is food for thought
another variable to be accounted for,,,,,and I will take your suggest and invest in an M die

[joeb33050]

Depends on how work hardened your brass is. If the brass is hard enough it could possibly shrink the boolit some. Only way to find out is to pull a loaded one.
Best wishes from the Boer Ranch,

Joe
Seated 311299s, wheelweights, sized to .3120" in ~ 6-times shot FL sized and M died brass. Pulled them out with a pair of pliers-they were in there tight!!
Measured the bullets at .3117" to .3119", mostly .3118" or .3119".
So they did get sized down, .0001" to .0003".
joe b.

[Bret4207]

Anneal your cases Joe and it may be less than that. I've often wondered if the Lee FCD isn't the answer to this. Lets say you size your annealed or new brass and use and oversize expander button. What happens when we seat the boolit? We stick it in a standard seating die and mash the boolit all to heck. Seems wrong to me. Using a Lee FCD we can adjust things so the minimum amount of "crush" is applied. I don't know for sure it'll work, but in theory the collet should offer some "leeway" (pun intended).

If you read Dr.Manns book or "The Modern Shuetzen Rifle" you'll find some info there. The Shuetzen boys have a lot of info on this.