Neck Expanding Die for 300BLK needed?

[MFInc]

I already have the RCBS FL die set. I've seen videos where they weren't used, and then read that a neck expander die is necessary for proper bullet seating with that cartrdige. TIA

 

[45/30-06OKIE]

I already have the RCBS FL die set. I've seen videos where they weren't used, and then read that a neck expander die is necessary for proper bullet seating with that cartrdige. TIA

The only difference in a full and a neck sizing die is the neck sizing die only resizes the neck. They should both give you proper neck tension. In a semi auto you need to full size though.

 

[Varminterror]

The only difference in a full and a neck sizing die is the neck sizing die only resizes the neck. They should both give you proper neck tension. In a semi auto you need to full size though.

He's talking about neck expanding, not neck sizing vs. full length sizing.

 

[Varminterror]

If you're shooting cast in 300blk, you might want a "lip" flaring die. It's also beneficial to have a mandrel expander for 300blk if you're forming from 5.56/223 brass, since you may either end up neck turning, OR choose to live with thicker necks than you might otherwise find in factory BLK brass.

"Necessary?" Eh, probably not. A good idea? Yup. Cheap? Yup...

 

[Click_Here]

May depend on projectile type. I could not get flat base projectiles properly into the case mouth without flaring. BT, no problem.

 

[45/30-06OKIE]

He's talking about neck expanding, not neck sizing vs. full length sizing.

Hmm OK, sounds like you know more about that than I do, lol! I have only ever used a standard sizing die and other than two separate bad 308 and 30-06 dies from the Red H company, I haven't really had many issues with neck tension.

 

[Varminterror]

May depend on projectile type. I could not get flat base projectiles properly into the case mouth without flaring. BT, no problem.

Bingo.

I tend to chamfer my mouths enough to let flat base bullets start into the case freely, but if guys aren't trimming 300blk brass (and a lot don't), then adding a slight "lip" flaring step can help a lot. I don't really want to flare enough that I consider it to be flaring the "mouth," but only just enough so the "lip" of the mouth will let a full diameter flat base set into the case mouth, or "lip". I don't crimp my bottleneck rounds, so it does kinda stink to need to run the seating die deep enough to iron out that flare as well - so generally, I prefer to chamfer a hair more and ensure the bullets will get started that way instead of adding two relatively unnecessary steps to the sizing and seating processes.

 

[EricBu]

I already have the RCBS FL die set. I've seen videos where they weren't used, and then read that a neck expander die is necessary for proper bullet seating with that cartrdige. TIA

I only expand the necks when I'm loading on an automated press and using a bullet feeder, OR if loading cast bullets. I can't recall if I'm using an M Die or not, I've been switching to m-dies for everything, don't remember if I've gotten to 300blk yet or not.

 

[Click_Here]

Bingo.

I tend to chamfer my mouths enough to let flat base bullets start into the case freely, but if guys aren't trimming 300blk brass (and a lot don't), then adding a slight "lip" flaring step can help a lot. I don't really want to flare enough that I consider it to be flaring the "mouth," but only just enough so the "lip" of the mouth will let a full diameter flat base set into the case mouth, or "lip". I don't crimp my bottleneck rounds, so it does kinda stink to need to run the seating die deep enough to iron out that flare as well - so generally, I prefer to chamfer a hair more and ensure the bullets will get started that way instead of adding two relatively unnecessary steps to the sizing and seating processes.

That reminded me of my first conversion attempt.

I'll just add this for a good read (or not). Theres some tutorials and random forum posts out there about cutting your brass to a shorter length before forming so you don't need to trim to proper length. Speaking from experience its fine but if you use a combo seating/crimp die you're most likely going to run into problems. Cutting Jigs and Harbor Freight Mini Chop Saws are not precise tools, the jig may have some play, the base of the saw may not be square, the blade can flex etc.... Take your pick of non-precise features to not get a square case mouth.

TLDR - non square or varying length case mouths are not friendly to seating/crimp dies. Dial it in on a short case and the next long case activates too soon buckling the baby 300 blackout shoulder EASY and its hard to tell unless you have a tight case gauge from Sinclair.

YMMV, but thats one of my noob events.....did I ever tell you guys about the time I dropped a powder charge in a case with no primer in it?...Maybe some other day.

 

[mcb]

I have not in my loading of 300 BO including flat base bullets like Barnes 110gr TAC-TX and Speer 125 gr TNT. I do my 300 BO loading on a Dillon XL 650 but without a bullet feeder if that matters.

ETA I do trim all my 300 BO brass and chamfer them lightly.

 

[MFInc]

I failed too mention I'm currently going to be using already formed 300 brass shot by me. A mix of factory and converted brass. Not converting any 5.56 brass yet. Figured I needed to chamfer the cases anyway after trimming. But reading these replies I think I'm ready to go with the gear I have. Thanks for the reply's.

 

[Walkalong]

I have used factory and converted .223 cases for 300 BLK. I use the standard expander ball in the sizer die, but I do deburr and chamfer the cases, have had no need to use a separate expander or anything to lightly bell the case mouth. Most have not been flat base, but I have loaded the flat base 110 Gr V-Max and the 130 Gr Hot Core FP (2nd and third pic) with no issues. I mostly don't use flat based bullets, but it’s not on purpose.

 

[BW460]

I use a Lee universal expander to just kiss the mouth of the case. I only expand it a few thousands but that small amount makes a huge difference in how my flat base bullets seat.

 

[Click_Here]

I have used factor and converted .223 cases for 300 BLK. I use the standard expander ball in the sizer die, but I do deburr and chamfer the cases, have had no need to use a separate expander or anything to lightly bell the case mouth. Most have not been flat base, but I have loaded the flat base 110 Gr V-Max and the 130 Gr Hot Core FP (2nd and third pic) with no issues.I don't remember using any flat based bullets though.

What die are you using for the modified roll crimp? Its possible those with needing to expand are using small base dies. I am, thats 1.

 

[Bcwitt]

Flaring makes it much easier & less likely to damage or make the bullet go crooked. A badly crooked bullet leaves a distinct bulge on one side of the neck. It is definately worth the extra operation. Makes much better ammo.

 

[Kaldor]

I just have always sized with a Hornady FL sizing die after cutting with the HF mini saw. I do tumble the cases in SSTL media before sizing just to take the rough edges off. After FL sizing and trimming, they get trimmed and tumbled. I do use an M-die and Lee FCD while loading for a flare and light crimp to remove the flare.

The only real care I take is using all LC brass. The rest is pretty simple, even more so now that we convert using a Dillon 650 and RT1500.

 

[Walkalong]

What die are you using for the modified roll crimp? Its possible those with needing to expand are using small base dies. I am, thats 1.

I’ll have to look when I get home, but fairly sure it’s a Hornady seater/crimper.

 

[jmorris]

and then read that a neck expander die is necessary

Size dies generally make the case mouth “under” and the expander opens them back up. This takes care of wall thickness variation. If you had different wall thickness and size just by the OD, your ID would vary along with wall thickness, as Would neck tension.

Straight wall rounds often do have expander dies but most bottle neck rifle die incorporate the expander in the decapping stem. They can do this because they are down inside the body while the neck is being sized and then pulled back through.


Straight walled rounds don’t do this because you can’t expand the ID at the same moment you are sizing down the OD.

This is a Sinclair expander dir for rifle rounds, very few use dies like these, certainly not necessary.