Somebody help me out with neck tension....

[fw707]

Here's what I've got right now on the neck measurements with my .243 AI:

.277 on the fired cases
.266 after FL sizing in a Redding die
.272 after seating a 105 A-Max

These measurements are the OD measurements of new Lapua brass.

 

[Rthur]

Re: Somebody help me out with neck tension....

How does this load shoot? Maybe a little to much neck tension. A neck sizing die with a .269 bushing(.001 spring back with .002 neck tension)
good luck
Rthur

 

[fw707]

Re: Somebody help me out with neck tension....

Rthur, thanks for the reply.
I posted the specs because I was wondering about the neck tension. It seemed a little too much for me too.

 

[MALLARD]

Re: Somebody help me out with neck tension....

i wouldnt say its allot but im not sure if you need that much ,i think .005-.003 is pretty normal , so if your doing .006., its not "bad" , how are your groups ?

 

[jdgray]

Re: Somebody help me out with neck tension....

To quote the great Richard Lee

"A bullet makes a poor neck sizing tool"

.002"-.003" is all you want, some like less. The brass is just to thin or weak to gain tension after a few thousands.

 

[alton]

Re: Somebody help me out with neck tension....

See if you can get a larger expander ball from Redding.

 

[fw707]

Re: Somebody help me out with neck tension....

Thanks guys.
The load shoots just fine.
I removed the decapper/expander stem from the die, so the neck is getting the OD sizing only. The bullet seating is feeling more consistant now, and the groups are as good or better than before.
I might look into a bushing die.

 

[TexIndian]

Re: Somebody help me out with neck tension....

Another (cheaper) option would be a Sinclair expansion mandrel. They are sized right at .308 so you get about .001 or .002 neck tension after springback.

But the bushing die would be more versatile in the long run, and produce less work-hardening on your necks.

 

[MALLARD]

Re: Somebody help me out with neck tension....

if you only use .002 tension its possible you could develope some delayed ignitions

 

[Mark Walker]

Re: Somebody help me out with neck tension....

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MALLARD</div><div class="ubbcode-body">if you only use .002 tension its possible you could develope some delayed ignitions </div></div>

???

I run .001-.002 in all my barrels and have never had an issue with delayed ignitions. Bench boys often run .0005 or so, no issues there either.

 

[turbo54]

Re: Somebody help me out with neck tension....

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: OldTex</div><div class="ubbcode-body">Another (cheaper) option would be a Sinclair expansion mandrel. They are sized right at .308 so you get about .001 or .002 neck tension after springback.

But the bushing die would be more versatile in the long run, and produce less work-hardening on your necks. </div></div>

The Sinclair expander die is a fantastic tool to have in inventory.

They have two lines of expander mandrels available for the die:

1. "Expander mandrel" - these are sized .001" UNDER nominal.... For a .308 bullet, the mandrel will measure .307"
2. "Neck Turning mandrel" - these are sized .002" UNDER nominal... For a .308 bullet, the mandrel will measure .306"

I always buy the -.002" neck turning mandrels for mine, which normally leaves me with ~.0015" neck "tension".

My sizing regimen includes a Forster bushing/bump die with a bushing that leaves the case ~.004" under nominal. Then the cases go through the Sinclair die, which necks them up to ~.0015 under nominal. Works great.

Remember that for sizing consistency, your brass must always be all the same hardness.

 

[JimGnitecki]

Re: Somebody help me out with neck tension....

I'm not sure I am following this.

Is the Sinclair "expanding die" a completely separate die?

If I am using a Redding match sizing die with bushing of correct size (based on bullet diameter .308" + brass thickness .0155x2 - .003" for semiauto =.336"), do I still even NEED any expander at all?

Jim G