Sizing mandrel vs neck bushing

[Jesse Jaymes]

The question would convey much more readily in conversation than in text, but inquiring about using a "Sizing Mandrel" or at least that is how I would term the tool.

I've run FL neck sizing bushings for many years. I generally work with bushing to get a tight enough seat to hold a bullet reliably, yet feel smooth, consistent and easy when seating.

Has reloading advanced to the point of using a neck bushing to undersize the necks a fair amount, but nothing in the realm of Overworked....then run up onto a tapered expander mandrel (which I am guessing in machined and polished to finish under bullet diameter a few thousands of an inch to account for spring back), then finish by seating a bullet?

Believe this makes neck tensions more consistent under the theory of pushing any neck thickness variations or inconsistencies to the OUTSIDE of the bullet seating space/area.....vs.....squeezing the neck from the outside...in (Neck Bushing) and having the bullet displace these variances and possibly having inconsistent seating sides or surfaces around the circumference of the bullet?


I've used a tapered mandrel to "iron" out dented cases mouths from factory new brass, as well as uniform a case neck and mouth for inner and outer neck trimming.

But I've never been educated on using a specific sized mandrel to open up and case to seating dimensions.

Am I way off base with this, or is this NOT a current/upcoming trend?

 

[nhyrum]

In my mind, mandrels have a few things going for them, or specific use cases. When turning necks, they get rid/help get rid of the "donut" that forms. I also believe they help get more consistent neck tension, bit I think that's more to do with turning. People that use mandrels are usually people that turn necks. I also believe they will make a straighter neck.

Now, this is all second hand knowledge for me. I've yet to use any, but I've been looking into them for a while.

Sent from my SM-G975U using Tapatalk

 

[rayporter]

your ammo will only be as straight as your die. if it is straight coming out of the die i would feel you can only damage it by using a mandrel. now if you are searching for a certain neck tension i may have to yield.

 

[nhyrum]

your ammo will only be as straight as your die. if it is straight coming out of the die i would feel you can only damage it by using a mandrel. now if you are searching for a certain neck tension i may have to yield.

My thinking is it's a lot easier to make a mandrel straight than it is to make the die body and the threads perfectly concentric and colinear with the press ram. Now... How much effect does that runout have and where you hit a point of diminishing returns... I think that's what gets me. I can't shoot good enough to require perfectly concentric rounds with neck tension measured to four decimal places ok maybe a little exaggeration there. I just go with decent dies with bushings. If I were to change, I'd get a custom one piece sizing die made with the perfect neck tension built in.

Sent from my SM-G975U using Tapatalk

 

[rayporter]

if you have a die and you push a case in with a very sloppy press the case still gets in and the press has no bearing on the case after it gets into the die. you get a straight case.

i think of it like pulling a case over the sizing button. this will make straight cases crooked.

yes you can make the mandrel straight but then i can see press threads and ram being off as you push a case that was straight onto a mandrel. if the mandrel is off in any way you just undid what the die did.

i bought a set of mandrels but i use them to get perfect necks when i turn necks.

totally agree with you on the rest.

 

[nhyrum]

yes you can make the mandrel straight but then i can see press threads and ram being off as you push a case that was straight onto a mandrel. if the mandrel is off in any way you just undid what the die did.

I think this is why most people that use mandrels use arbor presses.

Sent from my SM-G975U using Tapatalk