Why No Case Expansion?

[doc540]

I've reloaded my .223 brass three times now.

Resized on a Dillon 550B using RCBS dies.

Shot all of it in a Savage Model 12 bolt gun.

Case length is still only 1.751 - 1.755

They don't seem to be expanding to a length requiring me to use my new, Little Crow case trimmer.

Under what conditions should I expect them to need trimming?

Thanks, I'm having fun now!

 

[slippingaway]

Since you're using a bolt gun, you might not see your brass grow as much as someone using a semi-auto might. Bolt guns seem to have tighter chambers on them, so the brass doesn't expand as much. Semi-autos tend to have looser chambers to help with reliable feeding, which means the brass expands more when fired. Sizing that brass back down is what can lead to the cases "growing." Also, the specifics of some rifle chambers, especially in relation to the shoulder and neck, can cause more of an issue than others.

Also, are you using a full-length sizing die, or just a neck sizing die? If your ammo is only being used in this one firearm, you might want to just neck size it. The brass is now fire-formed to that gun's chamber, and neck sizing can give you even better life out of your brass.

 

[doc540]

Thanks

I'm assuming the RCBS die is a full-length die since when adjusting it, I bring the shell plate all the way up to the bottom of the case.

And after sizing it appears the die went nearly all the way to the bottom of the case.

New at this, so bear with me.

 

[slippingaway]

Sounds like it is. The label on the box for the RCBS dies should tell you, it should either say "F L Sizer" or "Neck Sizer." The die should also have a part number stamped into it, 11129 is the full length sizer, 11130 is the neck sizer.

 

[doc540]

Yep, full size it is.

thnx

Will a Lyman 5.56 neck sizing die work for .223 in my Dillon?

 

[Kevin]

Slippingaway:
I do believe you when you state neck sizing dies will make your brass last longer, than full length sizer. I've seen that before many places. What I don't understand is why? What does the full length sizer do vs a neck sizer? You make a good point, when you said the same brass from the same gun and that the brass would be sized to that chamber. That makes sense.

 

[slippingaway]

Every time you work brass, it gets a little bit more brittle. It's called work hardening, and has to do with the crystalline structure of metals (yes, they have a crystalline structure ). Think about what happens when you take a paper clip and bend it back and forth a few times. The less you work the brass, the longer it will last. With new brass, or brass that has been full length sized, the entire cartridge is just smaller than the chamber to ensure that the round will chamber in a firearm with a chamber that is machined to the very small end of the SAAMI specs. Since most chambers fall in the middle or even toward the top end, it leaves a lot of room between the chamber and the brass. When you fire the round, the pressure expands the brass outward until stopped by the chamber, and the brass then springs back just a tiny amount, allowing it to be extracted.
When you full-length size the brass, the die returns it to that small size again, working all that brass. Every time you fire and full length size, it works the brass on the entire cartridge, including reworking the shoulder of the cartridge.
In comparison, a neck sizer only works the small neck of the cartridge, and leaves the rest of the brass alone. Because the tolerances on the neck area of the chamber are generally held tighter, the neck doesn't expand as much. It just needs to be worked a tiny bit to hold tension on the bullet. Because you're only working a small amount of the brass, and you're working it a relatively small amount, it doesn't work harden as much or as quickly.

I hope that makes sense.

 

[mattsbox99]

Pretty well explained Slipping.

Just to add, you will still have to FL size every third or fourth time if you only neck size. Also, the brass work hardens over time from firing, so annealing combined with the neck sizing is the best way to achieve long case life.

Using that process I've seen a 338 Lapua case be reloaded nearly 40 times. With straight FL sizing and no annealing you would be lucky to get 6 reloads out of it.

 

[M'BOGO]

Last night I composed a pretty good set of instruction, quick and easy way to use a standard full length die to neck size, and it's not here? Stoopid puters....Insert angry faced fist shaking guy here...

Try again tomorrow...

 

[Kevin]

Slippingaway: Thank you for that detailed explanation. I have been curious about this matter for a while. I reload for .220 swift. The die set I bought several years ago was a Full Length set, because, at the time I didn't know the difference. I'll be looking for a new set.

 

[6gun]

Cases as small as a 223 just really don't expand much length wise, even my 30-30's never expand enough to need trimming, there is no rule that says cases will need trimming.

 

[doc540]

I've been told I can readjust my full length die to only resize the .223 neck.

Tested it using a felt tip pen today and, sure enough, it just resizes the a portion of the neck.

 

[mattsbox99]

I do that with my .22 Hornet, although I only resize the part of the neck that holds the bullet.

For the most part, I do what is known as PFLR, or Partial Full Length Resizing. That basically accomplishes the same thing as neck sizing but screwing the die all the way down like full length sizing, but then backing it off 1/4 turn.

A word of caution though, you can cause a 'donut' in the neck if you aren't careful. This 'donut' is where the brass flows to and thickens instead of just lengthening the case neck. It can result in a very high pressure situation. If you see a 'donut' form at the joint of the neck and shoulder, you need to outside trim the case to get rid of it.

 

[M'BOGO]

Doc, the post of mine that dissapeared had to do with the marker technique. Personally like to size about half of the neck, which will also kiss the body of the case.