mandrel for case necks...can somebody please explain

[Benman73]

Not sure how to properly word this question, so bear with me. When you guys use mandrels to set the neck tension, are they stand alone mandrels, like the old Sinclair mandrel dies that contain a mandrel that's inserted into the top of the die, like what is used prior to neck turning? Or are you using body dies that contain a mandrel that would hold the cartridge case in place when running the mandrel into the neck? I have an old set of Sinclair neck expanding mandrels labeled "E" and "T" and the die they go into, but am unclear if this or something similar is what you guys are using when using mandrels to set neck tension.

Also, from a consistency perspective, would initial case neck turning followed by full length sizing with a custom honed neck (Forster die) give similar results to the mandrel operation after using a bushing die?

I don't have any way to measure run out and I'm not a bench rest shooter so I probably couldn't shoot the difference, but I am both genuinely curious and unclear about the mandrel sizing operation.

Thank you

 

[Beluebow]

When you guys use mandrels to set the neck tension, are they stand alone mandrels, like the old Sinclair mandrel dies that contain a mandrel that's inserted into the top of the die, like what is used prior to neck turning?

Yes....E is for expander and T is for turning arbor.

 

[Dragoon300]

The mandrel is mounted in its own holder and is used like a die, and is the last sizing operation. I don't turn my case necks, not that it's bad, I don't need to yet. I select a bushing that brings my case neck approximately .002 under my target ID. Then run the mandrel to size the neck up to my target ID. This pushes the inconsistent wall thickness outward, and leaves the neck at the proper ID. As has been said many times in this discussion, pushing a mandrel in is less likely to distort the case shoulder / neck and cause run out, than pulling an expander ball out of the neck. This and neck tension are the primary reasons for using a mandrel.
Hope this helps, cheers!

 

[Benman73]

Thanks for the info guys, that does help clear things up.

 

[sedancowboy]

Not sure how to properly word this question, so bear with me. When you guys use mandrels to set the neck tension, are they stand alone mandrels, like the old Sinclair mandrel dies that contain a mandrel that's inserted into the top of the die, like what is used prior to neck turning? Or are you using body dies that contain a mandrel that would hold the cartridge case in place when running the mandrel into the neck? I have an old set of Sinclair neck expanding mandrels labeled "E" and "T" and the die they go into, but am unclear if this or something similar is what you guys are using when using mandrels to set neck tension.

Also, from a consistency perspective, would initial case neck turning followed by full length sizing with a custom honed neck (Forster die) give similar results to the mandrel operation after using a bushing die?

I don't have any way to measure run out and I'm not a bench rest shooter so I probably couldn't shoot the difference, but I am both genuinely curious and unclear about the mandrel sizing operation.

Thank you

To help clear things up a little more. The "E" expander is .001 smaller than nominal bullet dia and the "T" expander is .002 smaller. So with a .264 bullet dia. you would expand with the .263 "E" and turn with the .262 "T" expander. To get the grip I want I use the T expander mandrel when only sizing cases to reload.

 

[Shawn Carverelli]

The mandrel is mounted in its own holder and is used like a die, and is the last sizing operation. I don't turn my case necks, not that it's bad, I don't need to yet. I select a bushing that brings my case neck approximately .002 under my target ID. Then run the mandrel to size the neck up to my target ID. This pushes the inconsistent wall thickness outward, and leaves the neck at the proper ID. As has been said many times in this discussion, pushing a mandrel in is less likely to distort the case shoulder / neck and cause run out, than pulling an expander ball out of the neck. This and neck tension are the primary reasons for using a mandrel.
Hope this helps, cheers!

great explanation...I can hardly wait to try this out when my new mandrels show up by carrier pidgeon

 

[Shawn Carverelli]

I haven't pulled an expander button/ball up through a case neck in decades. Doing so can definitely create inconsistencies. I have been using bushing dies for quite some time and have had excellent results. Virtually all of my rifles will shoot <.5moa @ 400yds with carefully tailored handloads. I only own "hunting" rifles and the level of accuracy that I'm getting actually exceeds my needs.

Using mandrels might make my ammo a bit more consistent, but I doubt I'd be able to see anything on paper at the distances I shoot. If you're shooting competitively at long range than the use of mandrels may show some on-target improvement but beyond that, I don't see the benefit.

seems like we aim for accuracy @ 1/2 MOA when all we actually need is MO prairie dog.
Then again...sometimes all them little buggers give ya for a sight picture is the top of their head and an eye over their dirt mound

 

[FEENIX]

When you guys use mandrels to set the neck tension, are they stand alone mandrels, like the old Sinclair mandrel dies that contain a mandrel that's inserted into the top of the die,

Yes Sir, same concept. I use the 21st Century version.

 

[DUSTY NOGGIN]

Please pardon my ignorance, one camp says bushings push any variance in and the other says mandrels push it out, okay I got that.
If my bushings push the inconsistency to the inside doesn't the bullet push it back out, like a mandrel?

both are right , consider neck wall thickness variations between different brass
some can be .011 @ 6 oclock but .015 at 12 oclock .. if measuring runout , you could be at .002 off ( .004 split ) , just because the neck isnt in-line with the body ,
a full length bushing die will push the ID of the neck off center ( compared to case body ) because its sizing the case body and the neck at the same time . if ,with a .004 ( as above ) -- ya gotta split that equaling .002 ... now your jump is .020 off on the 12oclock side and .012 on the 6 oclock side ....... is that gonna engrave the bullet into the rifling straight ??? maybe ???

the 2 camps buying 2 different brass makes , can both be right

even if you mandrel after there is nothing to support the side wall and hold on axis , the damage is already done ( if you had neck wall variation ) if you just expand it it can still be off center

that is why turning uneven brass or using decent brass , before this with bushing , then mandrel , you can end up with good tension and stay on axis

make or verify what youre using is good brass and ignore all that ^^^^^^


that is why i wish they made a 2 stage full length mandrel die -- something you can press a mandrel through while being held in the die during length full sizing

 

[Shawn Carverelli]

if I understand correctly, with new brass no resizing is neccessary except straightening and expanding the brass neck with a mandrel the chamfering the inside of tbe neck and load as per usual.
Fired cases are resized with a neck bushing around .003 under loaded dimension and then expanded a hair with a mandrel then loaded.
But woukdnt the neck of fired cases already be straight if your chamber is cut straight.
Why wouldn't the appropriate neck bushing be enough at this point to set the right tension for fired cases.
My new t7 turret press gets here today and I'll be on the shoo in afew hours putting some loads together.
also, with the press I ordered a set of competition shellholders and Im not sure why I did. What are they for? Seems like they're a tad different by a few 1/1000ths of an inch

 

[QuietTexan]

But woukdnt the neck of fired cases already be straight if your chamber is cut straight.
Why wouldn't the appropriate neck bushing be enough at this point to set the right tension for fired cases.

The mandrel shouldn't be moving the brass much, if any, and is really there just to push any thickness variations outwards and be a more accurate final setting before seating. Mandrels are to the half-ten thou rather than the full thou, and easier to confirm dimensions on.

Comp shellholders work in a specific situation - you set the sizing die on the tallest one, and if you aren't getting the bump you need as the brass hardens you swap in the next shorter one and the die pushes 0.002" tighter (because the case goes into the die 0.002" further) and you should be back to bumping where you were with the first holder. IMO they'll just mess up your other dies if you change them around, I'd personally rather adjust my sizing die.

 

[Shawn Carverelli]

The mandrel shouldn't be moving the brass much, if any, and is really there just to push any thickness variations outwards and be a more accurate final setting before seating. Mandrels are to the half-ten thou rather than the full thou, and easier to confirm dimensions on.

Comp shellholders work in a specific situation - you set the sizing die on the tallest one, and if you aren't getting the bump you need as the brass hardens you swap in the next shorter one and the die pushes 0.002" tighter (because the case goes into the die 0.002" further) and you should be back to bumping where you were with the first holder. IMO they'll just mess up your other dies if you change them around, I'd personally rather adjust my sizing die.

excellent direction. So if you wanted to bump the shoulder back a hair so the cartridge will chamber, you can use a tad shorter shellholder or just adjust the sizing die 1/16 turn lower incrementally until it chambers with no resistence. I think I've got it...Thanks a bunch.
I opened the box for my new t7 press. Looks well made
Looks like 10mm mounting holes. Ill pick up the hardware tomorrow morning and get it set up.

 

[Longtine88]

New brass I only use a mandrel

Used brass I use a FL busing die with a bushing to 0.002" bump of shoulder then mandrel. Works for me several loadings. No problems. No runout. Itty bitty holes

 

[justinp61]

The mandrel shouldn't be moving the brass much, if any, and is really there just to push any thickness variations outwards and be a more accurate final setting before seating. Mandrels are to the half-ten thou rather than the full thou, and easier to confirm dimensions on.

Comp shellholders work in a specific situation - you set the sizing die on the tallest one, and if you aren't getting the bump you need as the brass hardens you swap in the next shorter one and the die pushes 0.002" tighter (because the case goes into the die 0.002" further) and you should be back to bumping where you were with the first holder. IMO they'll just mess up your other dies if you change them around, I'd personally rather adjust my sizing die.

Half-ten thou, .00005" or half-thou, .0005?