Mandrel as last step?

Dragoon300

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Speaking from an industrial brass tube forming background, the best way to get a consistent fit in the case neck on the bullet is by sizing the neck OD with a bushing down to where the neck ID is slightly smaller than the desired ID dimension. Then using a mandrel size the neck ID up to where the ID after spring back is the desired dimension. You may need to use a slightly larger mandrel to allow for spring back. This method is not reliant on consistency of the neck wall thickness to achieve the desired ID. So you do not need to be concerned with turning neck OD's to get a consistent ID. That said you may want your neck OD consistent for other good reasons like chamber fit and concentricity. This method is also better in the way expanding forces are applied to the brass pushing down toward the shoulder has more support, opposed to pulling away from the shoulder with an expander ball stretching the shoulder which is a leading cause of excessive bullet run out.
I too have loaded for many years in the traditional way with regular dies, then match bushing dies, and have turned necks as well, all have their place. But why I never thought about using a mandrel until recently when it started to catch on in precision reloading, I will never know. I just was not thinking of how we size tubes on machinery we build, and didn't put that knowledge to use in my reloading. I just did what the experts said to do, using what was being sold. I am very happy using mandrels now, and have had improved my ammunition, improving my rifles accuracy. Either way can acheive accuracy, which way is best? My vote is for the mandrel.
 

GatorTrapper

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Has anyone performed a side by side test of the grouping of cases sized with bushing dies with no neck expander vs mandrel formed cases ?
 

Mram10us

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If you think 1/2" 5 shot groups assure hunting success, God bless you.

I've killed well over 100 big game animals with guns, none of which shoot 1/2" five shot groups.
I wouldn't take a rifle that didn't :) hunting here might be different though. We all take the most accurate rifles (group wise) and take them out to 1000-1500 for dope. If they do well, they go hunting :)
 
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Mram10us

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Has anyone performed a side by side test of the grouping of cases sized with bushing dies with no neck expander vs mandrel formed cases ?
YouTube. Can't remember if the guy took out the expander ball or not but he used a mandrel v bushing dies
 

coyotezapper

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Been using Redding type S bushing dies on 3 rifles for awhile with great results but have seen in different forums people removing the the expander ball and using a mandrel as last step. So if you use a mandrel as a last step, wouldn't that throw off your desired neck tension?
As an example, I have a .310 bushing to use on my upcoming 7SS using ADG brass for desired neck tension. If I get a K&M .284 mandrel does that throw off my desired and planned neck tension established with the bushing?

School me on this please and thanks in advance!
Yes, remove the expander ball and run expander mandrel last. Many benefits including consistent neck tension / bullet release / lower ES SD.
 

Labwhisper

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I'll try an analogy.
While tightening a connection fastener (a bolt), and you reach a point where turning force no longer goes up.
Is it a good idea to continue turning?
Does it make a stronger connection to stretch the bolt shank well passed it's yielding point?
Answers: No, and No
I'm sure most here have experienced this in their lifetime. You just know you're screwed right there, and hoping with all you got that you can get the bolt back out (to replace it) without the head snapping off..

A common bolt connection is in proper tension while it's bolt shank has stretched, but not so far as to yield. When you loosen such a connection the bolt recovers it's form and can be re-used.
Where you go beyond this, the bolt yields, the tension it provides is not going up much, or at all, or is going down, and it will never recover it's form.

Back to reloading.
When you seat bullet bearing into excess interference fit, you cause neck brass yielding(up sizing). While there is high frictional forces required to do this work, the tension that grips the bullet (squeeze force) is not going up. And when you then pull that bullet, you find that the neck does not recover. It only springs back ~1/2thou,, it's normal amount, even if you had overcome fully 5thou of excess interference.
All you're doing with that is over-working the neck brass, while gaining no 'extra' tension.

To understand the futility in this you need to understand that bullets are not pushed out of necks on firing. Friction means nothing in this.
Instead, bullets are released from necks by their expansion, and even a relative few molecules worth of expansion fully frees the bullet.
That firing expansion is resisted by the neck's springback force times the area of bearing that force is gripping (PSI). Doesn't take much.

If pressure did have to overcome neck friction, internal ballistics would be completely different than it is.
In fact, if you were to force this, let's say by having zero neck clearance(not interference, but truly zero clearance), your gun would explode.
That is, unless you greatly reduced the friction to prevent this(so much so that your bullets would never hold set seating depths).
On our scale of things, including timing, it's hard to picture but very real. And you can test it & prove it (without dying).

Ideal mandrel use is a 'pre-seating' operation.
The mandrel would be at cal/bullet diameter. It would perform any neck upsizing so that your bullets don't have to (they're terrible expanders).
When you remove the mandrel the neck will spring back (inward) ~1/2thou, ready for actual bullet seating.
There is no difference in this from what you already do with your bullets.
To adjust your tension go to FORCE X AREA [pounds of force per square inch].
Adjust the LENGTH of downsizing to spring back against bearing (with that force of springback).
I had a wife once. If I did not use the right words (her words) then we could not communicate. Seems there is a lot of that going around. Semantics sure does get in the way of positive information exchange.
 

Mikecr

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We are wrong for taking out the most accurate rifles to long range, build a dope then go hunting? :) Ok.
You had qualified most accurate as (group wise).
So I point out that precision and accuracy are different, ESPECIALLY w/regard to hunting.
If the terms seem the same to you, then I suggest you look them up and consider the differences.

You implied "we all take the most accurate rifles (group wise)"", but we don't all do that.
Some of us develop for best cold bore accuracy -instead of best precision.
This often forces the compromising of best grouping for better accuracy.
And that's what some of us carry into external ballistic development.

Yes, I do not dismiss errors for semantics. Instead, I assume you mean what you say.
Others could as well, so it could be counterproductive to just be a 'nice' guy & let you mess up their thinking.
That's tougher for me to do - because I care.
I actually do not want people(including you) messed up on this stuff.
 

Alex Wheeler

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Groups and cold bore accuracy should be the same thing. Smaller groups, closer to center cold bore shots. If a barrel does not put the cold bore shot in the group its scrap.

Neck tension can be set with bushings or mandrels, winning BR shooters use both methods. Experimenting is what will lead to your success. If you dont try something you wont know. I have rifles that are tuned from .0005" neck tension to .005" neck tension. All verified through testing at 1k for group size and consistency. .001" in neck tension (interference fit) often makes a huge difference in groups size even if its past the yield point of the brass. One thing I do see on a regular basis though is that light NT and heavy NT seem to work, while mid range never seems to end up being the best. Usually I will end up .002" or less or around .005". Rarely does .003-.004" win out. Just an observation, not a rule.

Don't take anyone'e advice as fact, often times a new shooter will stumble on to something great that catches on because us "experienced" shooters wont even try it because we "know" it wont work :) Its happened with me and some of my new shooters over the last few years and they have pushed the accuracy envelope just by trying something totally different.
 

Mram10us

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You had qualified most accurate as (group wise).
So I point out that precision and accuracy are different, ESPECIALLY w/regard to hunting.
If the terms seem the same to you, then I suggest you look them up and consider the differences.

You implied "we all take the most accurate rifles (group wise)"", but we don't all do that.
Some of us develop for best cold bore accuracy -instead of best precision.
This often forces the compromising of best grouping for better accuracy.
And that's what some of us carry into external ballistic development.

Yes, I do not dismiss errors for semantics. Instead, I assume you mean what you say.
Others could as well, so it could be counterproductive to just be a 'nice' guy & let you mess up their thinking.
That's tougher for me to do - because I care.
I actually do not want people(including you) messed up on this stuff.
The "we" was referring to those I hunt with here, not the forum. I would hate to dismiss that error for semantics :) sorry, cant help myself. We will disagree and that is ok. God bless you Mike.

Alex, more replies from you would be nice Since you live thus stuff more than almost anyone I've come across.
 

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