using mandrel for neck tension

[kingfamous]

Just had a quick question for using a mandrel for sizing inside neck for proper tension. Is this only done once like neck turning, or is it done after every firing prior to sizing?

[ar15barrels]

It depends on how you are processing your brass.
If you are neck turning to get the necks the same thickness and then using a bushing die or a sizing die with the neck honed to size your brass to a specific size, the mandrel would only be used before neck turning.
If you are not turning or using bushing dies or a honed die to eliminate excess sizing, you need to use the mandrel after each resizing to get rid of the excess neck sizing.

[kingfamous]

I was going to use the mandrel to get the inside necks uniformed and then use a bushing die in a full length sizing die with out the ball. No neck turning.

[J-cat]

Mandrels are used on sized necks, not on fired necks.

[Donnovin]

I was going to use the mandrel to get the inside necks uniformed and then use a bushing die in a full length sizing die with out the ball. No neck turning.

That sort of puts you back to square one without benefits. In brief, since the thickness of the brass at the neck is not typically uniform, for improved consistency, you would either:

1) Use a mandrel to establish uniform neck tension, after sizing,

Or,

2) Use one mandrel to establish a round opening, then a turning mandrel (slightly smaller dia) to turn (cut) the necks to establish uniform thickness at the neck, then a bushing die or custom die when sizing to establish uniform neck tension.

I have done both, and now prefer option 1 as it is much simpler and gives me very consistent neck tension. Faster too.

I have read that there are good reasons to turn necks, as related to tighter custom chambers, etc, all beyond my pay grade and shooting skills.

[kingfamous]

Yes, I will be doing option 2. Mandrel to establish uniform necks, then re size and then with the bushing size the necks for .002 tension.

[kingfamous]

I just wanted to know if Im using the same brass, do I have to mandrel every time or just initially ?

[Donnovin]

Yes, I will be doing option 2. Mandrel to establish uniform necks, then re size and then with the bushing size the necks for .002 tension.

If you do not turn, ie, cut, the necks to a uniform thickness you will be wasting your time.

Think about how a mandrel alone can establish uniform neck tension since it sizes the opening from the inside. Perfectly round mandrel creates a perfectly round opening of consistent diameter. Then contrast that with how a bushing die establishes neck tension as it sizes the opening from the outside.....if the necks aren't turned and the thickness of the necks is not uniform, then the bushing will just push that lack of uniformity into the opening, and your neck tension will not be uniform.

[JagerDog]

What they said. What you've described is nonsensical.

[Meety Peety]

Mandrels are used on sized necks, not on fired necks.

This. If you try to run a mandrel on a fired case before resizing, it will be a hotdog in a hallway, wont even touch the neck.

[kingfamous]

https://youtu.be/l14kN55y5zs

this guy is describing what I wanted to do.

[Meety Peety]

Like any tool, an expander mandrel can serve multiple purposes and be used to solve more than one problem. In your video, it sounds to me like he is using it to repair dented necks. This works because when a neck has a good size dent in it, the dent artificially reduces the diameter of the fired case and when the mandrel passes through, it bumps the dent out. But running a mandrel on a neck that has been fired and is not dented is not going to net much in the way of results. Measure the neck ID of a fired piece of brass and then measure the OD of your mandrel. You will see that in the absence of a dent, the mandrel isn't really doing much prior to sizing.

So based on your video, the answer to your question of "how often do I need to do this" would be any time you need to repair a dented neck. Sounds to me like the guy in the video is running every piece of brass on the mandrel dented or not, and that's not going to hurt anything other than maybe your arm if you prep a lot of brass.

A lot of people will size their brass without an expander ball in the die and then run the sized brass over a mandrel in a separate step. If you are doing that, you would want to do it on every piece of brass to maintain consistent neck tension. Some say that this also helps maintain more consistent neck tension on brass that has not been neck turned by pushing any minor imperfections to the outside of the case neck.

One process is to repair badly damaged necks prior to starting the reloading process and the other is a method used by some to set their neck tension. If you do the latter process, you will notice that minor dents in the neck will work themselves out when you size the brass and then put a mandrel through it afterwards as part of the regular reloading process. Which means you only really need to run the mandrel prior to sizing on the ones that have a severely damaged neck, and in that case you would do mandrel (just to remove dent), size, mandrel again (set neck tension). And a lot of the time if the neck is that badly damaged, guys will cull those from a match lot and use them for practice. But again YMMV. A big part of reloading is doing what you feel needs to be done to give you the most confidence in your ammo. Shooting is mental.

[LynnJr]

His video is good for dented brass only!!!
The guys who are using a mandrel are not annealing there necks!!!
In the video he is annealing his necks so the only thing the mandrel does it remove dents.

The benchrest guys turn there necks and use a tight necked chamber meaning the brass is uniform in thickness it aligns better with the chamber and it moves very little when fired.

The tactical guys who follow benchrest techniques have it right but the vast majority of them would rather act snarky when they don't know why the process is used. I call it your too dumb to reload for a gun syndrome.

When you have a factory chamber the neck clearance is enormous meaning the brass expands five times as much as it does in a benchrest type chamber.
If you shoot brass once twice of three times without annealing the necks will show a huge variation in seating force often called neck tension. And yes it is measurable despite what one crazy guy always posts here who doesn't even own a modern firearm.
The use of a mandrel on non-annealed brass will lessen the neck tension variation case to case when measured using a force gage.
The process is to size all your brass first then use the mandrel to bring the case to case variation down.
You will see it used more and more on the bigger cartridges like 338,375,416 size brass were seating variation due to brass thickness is more common.
I will go and find the article about annealing now and link it here.

Okay here is the article https://www.ampannealing.com/article...he-microscope/

Watch the videos!!!!!
They will show you the variation found in sloppy chambers and why cartridges like the WSSM with bullets seated way past the neck/shoulder junction will never shoot well with a factory reamered chamber.
You will also notice they are measuring and showing tension differences in a graph.
The tactical guys are fun to drink beer with but don't know why they are doing what they are doing.
The benchrest guys are grouchy curmudgeons to deal with but they know how and why everything is done.
Good Luck!!!

[divingin]

I was going to use the mandrel to get the inside necks uniformed and then use a bushing die in a full length sizing die with out the ball. No neck turning.

The neck blows out on each firing. Sizing the neck brings that back to sub-bullet diameter, allowing the case to hold the bullet. Using a die that squeezes the outside of the neck may allow any inconsistencies in neck diameter to show up on the inside. In theory, using a mandrel will move those inconsistencies to the outside (i.e. the neck interior is more uniform.)

If you are going to use a mandrel to set your final (pre-seating) neck diameter, you have to first size the neck smaller than what the mandrel will open it up to.

If you use a mandrel and then size the neck, you're wasting the mandrel step, as you're squeezing the neck back down (and moving any inconsistencies back to the inside of the neck.) Mandrel should be the last step if you go that route.

IMO, it's easier to just size it to your desired diameter directly. If you're worried about thickness variations causing problems, neck turn to remove those variations. That's a one-time process.

To answer the other part of your question, yes, using the mandrel to set neck diameter is one of those every time you reload things.

[JagerDog]

Given the level of questioning, convoluted steps and the desire to use a mandrel, no neck-turning, etc., I might suggest a Lee collet die and call it good.