Sizing everything I know .

I've been inspired to address case sizing.

The inspiration come from "all of the top Bench Rest guys FL size every time" . Well they probably do , but they also have a FL sizer , dedicated shell holder if not cut and fitted as part of the ram on a roller bearing dial indicated press . The die is cut and finished to something most likely -.0015 all over , with a -.0025 on the on the neck from actual chamber dimensions and they fire a whole match with 1 case ...... .

In the real world a first cut chamber can be as much .002 over the standard drawing in every dimension and under by .0015 . The ideal is .003 under but a first cut die might be only .002 under standard and only.003 on the neck while a last cut dia might leave brass as much as .004 under standard all over and size the neck down .006 .
The possibility then is that a First cut die and a last cut chamber could come together and be somewhere perfect minimum sizing and "why won't the bolt close on 1/3 of my loads?". At the other extreme we get the short case life , frequent head separations , and flat primers .

Handloaders with some time in often practice bump sizing also referred to as short sizing , not to be confused with neck sizing in a FL sizer . They first discover when looking for that next -.5" that they have a long or fat body , long or fat shoulder , or even a short neck . Next they find that the die isn't exactly the same shape as the chamber , generally when they start buying 1x or have 2-3 arms in the same cartridge.

Spring back . Annealing will minimize this but it's a thing that happens even to very soft , thin brass . Here's where the guys that FL every time be cause the bench rest do say "I don't worry about it. I throw the brass after 3 cycles because it's going to crack necks , have head separations, or loose pockets after that anyway.". Typically this is a result of running top loads and having the fat chamber and skinny dies .

This all relates to new arms .

Make no mistake there are arm and cartilage combinations that are just really hard on cases , 303 Britt and Enfields come to mind immediately. Here is also a classic example of the chamber not being the same shape as the die . Many have sharp high angle shoulders vs the 30-30 like shallow angle .

When we get into older arms we sometimes find that wear takes a toll . In particular in the neck area and down to the shoulder l/body junction. I had an 06' that was about .001 off the minimum Go Head Space gauge , up to .004 is generally allowed it had a little throat erosion but on demand it would put 5 150 gr SPBT inside a half dollar at 100 yd . The shoulder measured .440 . New brass and factory ammo had literal wiggle room in the chamber, a fired had a .330 neck OD . Factory and full length ammo shot about 8" at 100 . This just 1 of a dozen or more examples I've had in my possession over the last 30 years . There was a 7.62×39 that in the course of a single firing cycle the neck moved .1 inch in dia , never mind the body . Of course that one is closer 8 mm than 7.62 . So when I champion neck sizing or leave .08-.1 of an 06' or similar neck unsized in an FL die it's experience not me say this is best .

Minimum sizing is the best for brass life .
If you need to FL size like another 06' I had needed, that's fine .
In many instances neck sizing works very well and it doesn't always need to be done every 3-4 cycles. Make notes and see where it leads you .

As for the tools obviously a FL die sizes everything that goes inside die .
Neck dies only do the neck .
Then you have the collet sizer that as I understand it sizes a portion of body , takes care of the shoulder length , and has a mandrel to limit the ID sizing in the neck .
Redding makes a body die presumably it sizes only the body .
Then there are bushing neck sizing dies . They allow one to not only only size the neck alone but to select dia for your specific needs . In my case I use one for a 6.5 to get the neck sized with a .270 ID to accommodate the .272 cast bullets.

I think I've covered all of the ground , but like all things I don't know it all and I am open to real applied experience and knowledge.

What a great post! You covered a ton of ground.

When I shot benchrest in the late 90’s early 2000’s everybody was neck sizing only, I forget what year full length sizing became popular on the benchrest circuit.

I neck sized everything up until about 7 years ago, I hated full length sizing and avoided it like the plague. I would deal with hard to chamber and heavy bolt lifts just to avoid the dreaded FL sizing die.

These days I just love the process, every part of it. I still neck size cases for particular rifles, mostly for reasons like you explained above. Most of my rifles receive partially FL sized brass, with the shoulder bumped .002”-.004”. This suits the majority of my rifles very well.

I did an interesting write up on the Swiss rifles page on Facebook. It is in three parts as I got time to play with things. It’s mainly about chamber dimensions and sizing dies and how it affected the ammo ballistically. It had some pretty interesting results, so if you like that kind of stuff it may be worth the read.


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