USING A CASE EXPANDING DIE ON 6.5CM CASES??

[chaz]

Hi folks,

I've been reloading for around 7 years now, and learnt an awful lot. Not withstanding there is still an awful lot to learn....

Recently, I've come across a "You-Tuber" by the name of Eric Cortina. Apparently he's a Pro US Shooter, who shoots nationally for the USA through the Lapua Brand in F Class. 

I've watched a lot of his videos, and they seem, (to my low knowledge of long range) ,to make a lot of sense.......

But the one thing I can't get my head around is expanding the neck on a fully neck prepped rifle case. Anything from 6mm to 7mm. Fully necked prepped, and sized case. That's already had the necks chamfered and de-burred. 

I've never heard of expanding the necks of cases just prior to powder drop then bullet seating. Is this less common over here in Europe. Or more common in the states? 

And is there much more benefit from doing this, and by roughly how much of the neck is best expanded???

Any constructive help appreciated....

Chaz.

[Deserttech Europe]

This is done to control neck tension.

An external bushing and internal expander mandrel allow the controlling of neck tension to an exact amount.

ewen

[Popsbengo]

2 minutes ago, chaz said:

Hi folks,

I've been reloading for around 7 years now, and learnt an awful lot. Not withstanding there is still an awful lot to learn....

Recently, I've come across a "You-Tuber" by the name of Eric Cortina. Apparently he's a Pro US Shooter, who shoots nationally for the USA through the Lapua Brand in F Class. 

I've watched a lot of his videos, and they seem, (to my low knowledge of long range) ,to make a lot of sense.......

But the one thing I can't get my head around is expanding the neck on a fully neck prepped rifle case. Anything from 6mm to 7mm. Fully necked prepped, and sized case. That's already had the necks chamfered and de-burred. 

I've never heard of expanding the necks of cases just prior to powder drop then bullet seating. Is this less common over here in Europe. Or more common in the states? 

And is there much more benefit from doing this, and by roughly how much of the neck is best expanded???

Any constructive help appreciated....

Chaz.

I believe it's all to do with neck tension and bullet release.  I have tried expanding .338LM after bush sizing (no button), I do think the batch felt better and more consistent on bullet insertion with an in-line die and arbour press (bags of feel). I measure run out and there was no improvement over just bushing - but again I get good run-out anyway from LE Wilson dies.

 I can't honestly say the on-range performance was noticeable but I have very consistent ammo anyway.  Can't afford to go chrono'ing too many variations with .338LM so no data to share.

I will experiment with 6.5CM when I can decide on exactly what diameter mandril to use.  A lot less costly to gather chronological data

 

[No i deer]

A bushing die sizes the neck on the outside and any discrepancies on neck wall thickness gets pushed inwards.. if you use the custom ground neck tension mandrels after it sets the neck tension from the inside of the neck and any discrepancies get pushed out. I run the neck tension mandrel all the way in the neck which also helps if your brass has donuts forming.. 

I'd recommend them 100 percent.. I use K&M custom ground neck tension mandrels.

If your using a standard seater and not a bushing die you will have alot of neck tension and the custom ground neck tension mandrel will work nicely. If you using a bushing die go down a bushing size so the mandrel works the brass a bit to get more uniform neck tension.

It's a very simple process and the bullets seat real nice..

Got mine from Spud.

There made to order unless he stocks them now.. there is alternate makes.. 

[DaveT]

Ditto the previous post.

I get my mandrels made by a local engineer / machinist.

[Gungrinner]

Been using the SINCLAIR EXPANDER MANDREL die for .223, 6.5cm and 308. Gives more than .001″ of tension, Mandrels can be polished up,  It's cheap and works very well. (Just make sure you get the seating expander mandrels and not the neck turning ones)

 

[Catch-22]

10 hours ago, No i deer said:

A bushing die sizes the neck on the outside and any discrepancies on neck wall thickness gets pushed inwards.. if you use the custom ground neck tension mandrels after it sets the neck tension from the inside of the neck and any discrepancies get pushed out. I run the neck tension mandrel all the way in the neck which also helps if your brass has donuts forming.. 

I'd recommend them 100 percent.. I use K&M custom ground neck tension mandrels.

If your using a standard seater and not a bushing die you will have alot of neck tension and the custom ground neck tension mandrel will work nicely. If you using a bushing die go down a bushing size so the mandrel works the brass a bit to get more uniform neck tension.

It's a very simple process and the bullets seat real nice..

Got mine from Spud.

There made to order unless he stocks them now.. there is alternate makes.. 

THIS ^^

I too also use the Sinclair Expander Die & Mandrels. I remove the expander button from my full length dies because they overwork the brass and rip the neck out of shape. Think about the brass going up into the die; on the upward stroke of your press, the expander button is pushed through the neck, opening it. The die then shrinks (sizes) the neck down. Then on the downward stroke of the press the expander button is pulled through the neck, opening it up again.
With an expander mandrel and die you’re only pushing the mandrel through the neck once, producing a very minimum size (giving normally around 0.02” neck tension). 
Therefore the expander mandrel works the neck less and gives a more precise (and minimum) neck tension.

[No i deer]

I think the button on the die takes out inward dents on the case necks on its way in and any outward dents being sized and neck tension is set really tight and on its way out as the die button is set for about 4 thousanths neck tension. I've not bothered to get a smaller button on my die as my loads shot great even though the brass is getting over work.. I now use a 2 thousanths neck tension mandrel on my 6.5x47 and a 1.5 thousanths mandrel on my 7mm's 

[alpha1]

I use L.E.Wilson neck bushing dies. I have a few neck expanders mainly from NOE bullet moulds over the pond. I also use their moulds for cast bullets I have just ordered a mould for my 6.5 Creedmoor.  I thought it would be fun to see if I can get it to perform with cast bullets as I rarely shoot past 300 yards.

[ds1]

So I’m in a minority of one here, I have a Wilson expander mandrel die and mandrels for 338 and 308. I get the concept but when I test rounds in two 338 rifles and one 308 rifle I find more consistent velocity ES without using the mandrels ( around 15 FPS for 10 shots, so still not ideal). I have tested it with varying bullet lengths ( seating depths) above and below the donut. No ES reduction. Concentricity - measured at the case neck and just back from the bullet ogive is always acceptable ( 4 thou or under) with or without a mandrel.

Bottom line is does it improve anything- ES, accuracy or runout - if yes great I’ll do it , if not I won’t. Just started using an Autotrickler so I will re-test the mandrel process again - it’s possible any benefit was getting lost due to consistency variations from the Charge MasterLite. 

[Popsbengo]

On 1/8/2021 at 12:36 AM, ds1 said:

So I’m in a minority of one here, I have a Wilson expander mandrel die and mandrels for 338 and 308. I get the concept but when I test rounds in two 338 rifles and one 308 rifle I find more consistent velocity ES without using the mandrels ( around 15 FPS for 10 shots, so still not ideal). I have tested it with varying bullet lengths ( seating depths) above and below the donut. No ES reduction. Concentricity - measured at the case neck and just back from the bullet ogive is always acceptable ( 4 thou or under) with or without a mandrel.

Bottom line is does it improve anything- ES, accuracy or runout - if yes great I’ll do it , if not I won’t. Just started using an Autotrickler so I will re-test the mandrel process again - it’s possible any benefit was getting lost due to consistency variations from the Charge MasterLite. 

Not a minority of one.  As I say earlier in the thread, I've tried it but can't say I'm particularly sold on the reported benefit.  I think if all other reloading steps are done well and the case prep is good it probably makes little difference - too little to see on the range in the statistical noise of all the other effects.   It certainly didn't give me worse results in .338LM

[chaz]

Cheers for the info folks. I was reading it wrong.  I thought he meant opening the case mouth like when reloading a 9mm pistol round. That kind of thing. But he didn't....

I'll carry on FL sizing without the decapper/expander ball fitted. Then size the neck with my mandrel die.

Cheers

Chaz.

[No i deer]

You can only but do you best brass prep possible and weigh the charges to the best you can't then it is what it is..

There really must be some testing/proof that the mandrels and other reloading techniques work like neck tension..

My shooting has improved since I started using the custom ground neck tension mandrels,annealing and bushing dies..

[DaveT]

DS1..... 15 FPS on ES is pretty spiffy....  if you mean SD then not so great.

IMHO Most brass prep beyond the very basics comes down to what gives you the most confidence that your rounds are made to the best standard that you are personally prepared to put effort into.

There may well be the 'law of diminishing returns'  as you apply more processes but I feel safe in saying that my shooting improves if I am happy that I have the best ammo I can possibly make.

It also reduces 'excuses' ! 😁

[martin_b]

>>I'll carry on FL sizing without the decapper/expander ball fitted. Then size the neck with my mandrel die

Exactly what i do for 6.5CM