Case Necks Aren’t Uniform

[Vyx313]

Alright, got my die cleaned up so it isn’t scratching the brass anymore…please tell me what I’m doing wrong now.

I left my dies setup the same way they were when I sized my virgin Lapua brass. Using a RCBS Matchmaster FL Bushing Die and a .287 bushing.

After running a few through I noticed the neck wasn’t sized all the way down. I started adjusting the die down so it sized more of the neck and the result are the attached pictures. Left to right is as I adjusted the die down more.

The right most case is about as far as it will go down while still allowing the bushing to move.

What the heck am I supposed to do at this point?

 

[CK1.0]

Maybe stop overthinking this?

Bushing dies don’t size the whole neck by design, don’t worry about it.

Adjusting your die down means you’ve probably bumped your shoulders too much creating a new issue that might actually matter and show up on target.

Before you over correct, remember, do no harm.

 

[Edsel]

Probably not what you want to hear, and I sense you’d want a solution for your dies - but it’s probably best to stick to regular FLS dies without the bushing and use a mandrel to dilate the necks.

Personal opinion - it achieves a better result and cuts down on the “complexity of the gadgetry.”

 

[Vyx313]

Maybe stop overthinking this?

Bushing dies don’t size the whole neck by design, don’t worry about it.

Adjusting your die down means you’ve probably bumped your shoulders too much creating a new issue that might actually matter and show up on target.

Before you over correct, remember, do no harm.

Overthinking myself into paralysis is my superpower. Lol

Thanks for clarifying that it’s not meant to size the entire neck. I’ll make sure the neck is in the same spot and that the rounds chamber and that’s pretty much it right?

 

[Edsel]

Thanks for clarifying that it’s not meant to size the entire neck. I’ll make sure the neck is in the same spot and that the rounds chamber and that’s pretty much it right?

The Forster Bushing Dies I use can size almost all of the neck, though - and depending on how one adjusts the bushing (usually to dodge donuts), you can choose size the upper 1/3 to 1/2 (typical settings).

 

[Rocketmandb]

I agree that bushing dies aren't supposed to size all of the neck, but the pics are showing less than half getting sized. I prefer more than that. On one of my dies, I remove the locking ring on the top of the die to get a little more space.

 

[Edsel]

@Vyx313

Can you show us a picture of your dies, and how they're set up?

Also, to ascertain just how much of your case necks are actually making contact, could you use a sharpie on them (sharpie on case necks > dry > run through bushing die)?

 

[Haney]

Does your die contact the shellholder , or come close to touching while sizing ? Have you tried taking the bushing out and setting it up for bumping the shoulder and then replacing the bushing ?

 

[CK1.0]

Set up your sizing die to bump your shoulder your desired amount (I use -0.0015” to -0.002”), don’t worry about the rest until after you’ve shot the stuff you make (and if there’s an issue).

FWIW/BTW, don’t get too OCD measuring things without considering that brass is Play-Doh as far as metals go, and things like shoulder bump probably won’t measure out truly consistent case to case until after 3-4 firings/load cycles on the brass (so don’t make yourself crazy).

 

[R_A_W]

but the pics are showing less than half getting sized.

It's probably too small a bushing. I think what is happening to the part that you'd expect to get sized is he is seeing really bad spring back towards the bottom portion of the neck, as that lower part resists sizing & the shoulder/neck junction "pulls" it back out. He's got a 0.287 bushing in there, which is pretty small for any .264 cartridge. That would give 0.000" neck interference on brass with 0.0115" neck thickness, or 0.007" interference for 0.015" (assuming no spring back)

@Vyx313 Lapua is pretty consistently right around 0.015", which would means you probably needs a 0.291 bushing if you're going to follow with a mandrel, or possibly a 0.292 bushing if not. Also, new Lapua is usually undersized, meaning you could just mandrel it out to the appropriate diameter, but you shouldn't need to run it through a neck bushing. Many just load it & shoot though.

Out of curiosity, what are the ODs of the neck about 2/3 the way down from the top on a sized piece of brass & an unsized piece of brass?

edit - bad at math this AM

 

[spife7980]

Adjusting the die in its external lock ring controls how far the body gets sized by shortening the case head to shoulder dimension. Set that up for sized brass to come out .002” shorter than the fired on the shoulder datum.

The bushing is installed in the die itself. Empty the die, paper towel it dry so there’s no lube, put the bushing in the die print side down and tighten down the top plug into the die until it bottoms out and the bushing stops wiggling. Then back out the plug ever so slightly so you can just hear it having room to click around when shaken which ensures it can move to self center.
It’s got a chamfer in the bushing so the case mouth doesn’t bottom out and jam on a square perpendicular edge inside the die. You won’t ever size the “entire” neck with it so there is always going to be a bit of unsized neck.

 

[Edsel]

Lapua is pretty consistently right around 0.015",...

0.0145" to 0.0150" from my notes...

 

[Vyx313]

This is a great community to get a lot of good input based on experience!

It sounds like I need to setup the die first to bump the shoulder .002". From there I'll get the die bushing setup so that it sizes at least half of the neck (this is roughly where I ended up with the rightmost case).

I am using a .262" mandrel after sizing. I may need to use a busing larger than the .287" bushing that was in there. That is just what I used on the virgin brass to give me some engagement with the .262" mandrel. This was giving me pretty consistent neck tension and the load I worked up had single digit SDs. I'll try a larger bushing and see if it's still getting consistent neck tension.

 

[Rocketmandb]

This is a great community to get a lot of good input based on experience!

Except for the few that are just batshit crazy.

 

[Edsel]

Except for the few that are just batshit crazy.

There’s a good many of them - racist, xenophobic trash…

Try using the site’s search function to look up common racial / ethnic expletives - results will yield page upon page of them. An endless stream of ugly bigotry and vitriol.

All this despite having a (token) “no hate will be tolerated” warning from Lowlight himself.

The more traffic, the more ad revenue - so in reality, it’s probably encouraged.