Question on expander mandrel

[josebd]

what size expander mandrel 6.5 creedmoor for .001 neck tension?

 

[6.5 forever]

I use Sinclair.
.263.
It works with Lapua brass.

 

[Tesoro]

,001 less that the diameter of your bullet!!!

 

[Benchrest Braxton]

i’d go with the black nitride mandrel from 21st century, they are 263 (1 thou below bullet diameter). with spring back you will prob be a little closer to a 2 thou interference fit after springback.

 

[Straightshooter1]

what size expander mandrel 6.5 creedmoor for .001 neck tension?

.264 - .001 = .263 But, you'll want to allow for springback. So I wouldn't go any larger than .2625 unless you just don't do any annealing, then .262 would be best. IMHO To be more precise, you can measure what springback you get with your brass and better figure what it'll take to get that exact neck tension.

 

[TylerFromMS]

Try using different bushings without a mandrel if you have a bushing die.

 

[Straightshooter1]

Try using different bushings without a mandrel if you have a bushing die.

The main thing I don't like about bushing dies is that they move the variations in neck thickness to the inside of the neck. Mandrels do the opposite.

 

[rwj]

The main thing I don't like about bushing dies is that they move the variations in neck thickness to the inside of the neck. Mandrels do the opposite.

True, but moot if you’re turning necks…

 

[rijndael]

The main thing I don't like about bushing dies is that they move the variations in neck thickness to the inside of the neck.

That's not limited to a bushing die though, right? Wouldn't a standard FL die do the same thing? It's only undone by the mandrel or the expanding ball.

 

[TylerFromMS]

The main thing I don't like about bushing dies is that they move the variations in neck thickness to the inside of the neck. Mandrels do the opposite.

Hmmm. Does it affect what’s on the target? Also, a bushing is generally allowed to “float”… that is, it never sizes all the way down.

 

[David Christian]

@josebd, short answer. Try using a bushing that sizes down to .261 ish, then experiment with a .262, .263, and a .264 mandrel/gage pin. Shoot them all and see what works for you.

Longer answer: You need to move the brass beyond it’s yield point when sizing, and then you need to move it back out beyond it’s new yield point with a mandel so that you generate consistent sizing across all pieces of brass. See this article on tensile strength testing:

The Science of Cartridge Brass Annealing

Want to know how annealing brass works? We examine the science here.

bisonballistics.com

If you don’t move the brass enough, you will have inconsistently sized brass.

 

[Straightshooter1]

True, but moot if you’re turning necks…

Yup.

That's not limited to a bushing die though, right? Wouldn't a standard FL die do the same thing? It's only undone by the mandrel or the expanding ball.

Yes, a FL sizing die will do the same thing to the neck and why it's best to use a mandrel afterwards and not use an expander ball. And the less you move the neck, the better before using a mandrel to get very low runout.

Hmmm. Does it affect what’s on the target? Also, a bushing is generally allowed to “float”… that is, it never sizes all the way down.

Though a bushing doesn't size all the way down, you still have the variances in neck thickness moved to the inside. That it doesn't go all the way down is good for avoiding the donut issue.

As far as effect on target, yes, there can be an effect on the target. The effect may not be detectable unless one is capable of shooting very small groups at very long distance. Or, is more easily detectable if the quality of the brass is poor, having large variations in neck thickness.

 

[josebd]

.264 - .001 = .263 But, you'll want to allow for springback. So I wouldn't go any larger than .2625 unless you just don't do any annealing, then .262 would be best. IMHO To be more precise, you can measure what springback you get with your brass and better figure what it'll take to get that exact neck tension.

I do anneal

 

[josebd]

Try using different bushings without a mandrel if you have a bushing die.

I don’t use bushings,I use forster fl die,with 6.5 creedmoor I get less than .001 runout on the neck or less

 

[josebd]

True, but moot if you’re turning necks…

I don’t turn necks

 

[TylerFromMS]

Though a bushing doesn't size all the way down, you still have the variances in neck thickness moved to the inside. That it doesn't go all the way down is good for avoiding the donut issue.

As far as effect on target, yes, there can be an effect on the target. The effect may not be detectable unless one is capable of shooting very small groups at very long distance. Or, is more easily detectable if the quality of the brass is poor, having large variations in neck thickness.

Is this capable? I mean, it’s a 6.5x47 and not a creedmoor, but it’s pretty close.

 

[TylerFromMS]

I don’t use bushings,I use forster fl die,with 6.5 creedmoor I get less than .001 runout on the neck or less

Dang. May have to try different mandrels for neck tensions, then. Or switch to bushing die and try different bushings.

 

[Tesoro]

I'd say you would have to be on the top end of the 1% of shooters on this forum to be able to isolate the effects of .001 and .002 nt on one's groups. And I aint one of 'em!

 

[nmkid]

I don’t use bushings,I use forster fl die,with 6.5 creedmoor I get less than .001 runout on the neck or less

I don’t turn necks

That's really amazing. What kind of cases do you use? Do you measure your necks?

 

[Straightshooter1]

Is this capable? I mean, it’s a 6.5x47 and not a creedmoor, but it’s pretty close.

View attachment 1384466

Could uses a little improvement . . .

. . . he says jokingly.