New lapua brass issues.

[Cody Richardson]

Picked up 300 pieces of new blue box 6BR brass. I conducted my standard brass prep procedure: trim to length, run through a 6mm expander mandrel, neck turn and inside/outside chamfer. Upon loading these seemed EXTREMEMLY easy to seat in an arbor press compared to once fired brass. Also I have had 11 of the pieces that would not hold a tight enough grip on the bullet. Should I run them through a F/L die and then through an expanded mandrel. Thanks for the help.

 

[Dusty Stevens]

You should run them into your die then load them. You dont wanna expand em back out after you get em sized- that puts em right back to zero tension

 

[dkhunt14]

I run brass through an expander mandrel. It doesn't open them up that much. Most measure .241 and will give enough tension. Was there lube from expanding and turning in the neck. I have different sized expander mandrels and tune my load with them. Matt

 

[jlow]

Expander mandrel 1st to open up necks more uniformly than they will be straight out of the box, then FL resize to generate the desired neck tension.

Agreed. The only thing I do differently is to size the neck with a bushing die instead of the FL sizer. Think of the expander mandrel as making your new brass like fired brass so that you can size them down to the final dimensions you want. If you don't expand them, Lapua brass can frequently have too much neck tension to start, this is the reason to expand them first but then you still need to size them back down.

 

[nmkid]

You should run them into your die then load them. You dont wanna expand em back out after you get em sized- that puts em right back to zero tension

Rusty...A little thick headed about what you are saying. I run my 6.5-284 brass through a 6-284 die then through an expander mandrel for neck turning. Are you saying I should then run them through the FL die again after neck turning? The OP says he had 11 cases that wouldn't hold a bullet at all. I have never run into that. After using the expander mandrel the case still holds the bullet tight enough that it can't be pulled out by hand.

 

[gsg5pk]

I always FL size new brass

 

[Dusty Stevens]

You should size your necks down after turning for proper bullet tension for forming. If your bullet measured .2435 and your expander is .243 you aint got much tension. You expand to match a turning mandrel thats not sizing your neck to accept a bullet. Of course you can do whatever you like- you can even super glue a bullet in place. For me im gonna size the neck properly before i seat a bullet no matter what stage the brass is in

 

[Shaggy357]

Been loading for 40 years and am unfamiliar with an "expander mandrel". (I don't shoot at paper.) From the conversation it sounds like a die with an oversized expander button used to open up a case neck. I learn something new all the time.

My new 6BR brass comes out of the blue box and onto the debur machine to remove any burrs that could scratch my die. They are then full length sized, trimmed to same length, and deburred again. Most of the Lapua brass have clean flash holes so I do not do anything there. I measure bullet, neck thickness, and ensure I have about .003 clearance in the chamber for expansion. I have 6BR, 6.5BR, and 7BR brass started this way. All are well under MOA out to 500 meters in my pistols.

Will an expander mandrel same me some steps?

Steve

 

[jlow]

This is an expander mandrel:


http://www.sinclairintl.com/reloading-equipment/case-preparation/neck-turning/turning-expander-mandrels/sinclair-expander-mandrel-oversized-prod33134.aspx


As already mentioned above, with new Lapua brass, it can come with too much neck tension and the expander mandrel is used to expand the necks out so that you can size it down to the dimensions you need.

 

[Shaggy357]

Oh, got it. Very similar to my turning pilots. Do these expanders only work in the expanding die, or will they fit the neck turning tool also? I sometimes wish my pilots were slightly bevelled on the end due to those few cases per 100 that are a little tight. The expander will fix that....may have to put one on the wish list and try it out......Only have two tight enough chambers to warrant it, and have @ 500 brass already turned for them...never know tho...probably a new barrel in my future.....

Thanks for the info.

Steve

 

[savagedasher]

Myself I like to shoot my brass one time before I do anything to it. If you have to turn the necks then turn them.
I feel any thing I can do to brass gets trumped by 50,000 psi inside the case.
Larry

 

[jlow]

Oh, got it. Very similar to my turning pilots. Do these expanders only work in the expanding die, or will they fit the neck turning tool also? I sometimes wish my pilots were slightly bevelled on the end due to those few cases per 100 that are a little tight. The expander will fix that....may have to put one on the wish list and try it out......Only have two tight enough chambers to warrant it, and have @ 500 brass already turned for them...never know tho...probably a new barrel in my future.....

Thanks for the info.

Steve

As with any situation where you are thinking of using a tool with another tool that it was not originally designed to be paired with, whether the Sinclair expanding mandrel will fit in your neck turning tool expander die is something you need to find out since we all use different turning tools.


What I can tell you is Sinclair makes a specific die that their expander mandrel drops into. The expander has a larger diameter body that prevents it from dropping too far down and a screw cap on the die prevents it from going too far up. I use a K&M neck turning setup and their neck expander for turning only fits their expander die as they have a threaded hole on the top that a screw on the die are used to lock them in and as such will not accept the Sinclair expander mandrel.


As gstaylorg has pointed out, the two expands to different degree and for good reasons and I would think they are not interchangeable in terms of function.

 

[Brians356]

Picked up 300 pieces of new blue box 6BR brass.

What's the significance of a blue box? I see this reference all the time, must have missed the memo.

 

[dkhunt14]

What's the significance of a blue box? I see this reference all the time, must have missed the memo.

The blue box is newer and the dimensions changed. The necks got thinner. Matt

 

[Dusty Stevens]

And they dont blow out as far on forming. 6br was the only brass that changed all other calibers are exactly the same

 

[Brians356]

You should size your necks down after turning for proper bullet tension for forming. If your bullet measured .2435 and your expander is .243 you aint got much tension. You expand to match a turning mandrel thats not sizing your neck to accept a bullet.

I can only refer to Sinclair's mandrels, but every Sinclair "expander" mandrel I own is exactly .0008" below bullet diameter. There will be some spring-back, so let's assume at least .0010" (and probably a bit more) below bullet diameter. That should be enough to grip bullets. We don't know the make or size of the OPs expander mandrel, so this is just a FWIW.

Now, Sinclair also makes "turning" mandrels, identical to their expanders, but smaller in diameter by .0013", so that would be .0021" smaller than bullet. The problem with prepping unfired cases with the turner mandrel is it just might not fully round out the neck and case mouth (if that matters.)

I would think a reasonable approach with unfired cases would be:

1. Expand with expander mandrel (to round out new neck)
2. FL or neck size
3. Expand with either a) turner mandrel or b) expander mandrel (depending on desired bullet tension).
4. Neck turning would require choosing 2. FL size, and 3.-b expander mandrel, if you follow Sinclair's advice.

 

[Brians356]

The blue box is newer and the dimensions changed. The necks got thinner. Matt

Thanks! I inherited a bunch of Lapua blue box brass. Is there a good thread on blue vs gold box Lapua I could review?

 

[Brians356]

You can check with Sinclair on their "Oversized" expander mandrels, but I believe the shank is the same size as for a neck turning mandrel. The main difference between the two is that the neck turning mandrels are ~.002" under bullet diameter, whereas the expander mandrels are ~.001" under caliber.

FWIW

Every Sinclair expander mandrel I own is .0008" below nominal bullet diameter. The turning mandrels are .0021" below bullet (or .0013" below expander.)

 

[Brians356]

Hence the "~", which means "approximately".

Hence the "FWIW". Some may find the extra precision of value. In this type of work, especially re: neck turning and bullet seating tension, it often is.

 

[Cody Richardson]

Ran the brass through my f/l die then expanded the necks. No issues. Seating pressure was all with in a 5-8 foot lbs. So I'm assuming that should mean consistent neck tension