Consistent shoulder set back with a Forster FL sizing die?

[thefitter]

Today I tried to set my Forster FL sizing die to FL size and set back the shoulder exactly .001

After a little trial and error I thought I had it. I measured a case, sized it and then measured again, .001 shoulder
set back. So I tried another, again shoulder .001 set back. Tried one more just to be sure (OCD) and it was .0015???
Tried another and .0015??

So I backed the die up a bit, but it still reads .0015 setback.

What is happening and how does a FL sizing die index for shoulder set back?

Thanks

 

[Heavies]

I've been having the same issue.
I am thinking it has to do with lube inconsisency and/or press flex. I have a Lee press, so I wouldn't be suprized if its the latter.
My other theory is that the cases have differing hardness. I found less inconsisency in set back after I annealed the cases.

 

[thefitter]

I've been having the same issue.
I am thinking it has to do with lube inconsisency and/or press flex. I have a Lee press, so I wouldn't be suprized if its the latter.
My other theory is that the cases have differing hardness. I found less inconsisency in set back after I annealed the cases.

Interesting. I have not got into anealing yet but it's on my list.

This was twice fired brass.

 

[watercam]

.0005" is a pretty darn small variation. You do not have a problem there. Is it possible there is variation in the measuring device(s)?

 

[duanepa]

Dimple in the primer(if it was there) on the "before" measurement?

 

[thefitter]

.0005" is a pretty darn small variation. You do not have a problem there. Is it possible there is variation in the measuring device(s)?

I guess it could be but I use a very good caliper and a base with the nose piece. Other thing is that it's a consistent variation, (if there is such a thing).

 

[thefitter]

Dimple in the primer(if it was there) on the "before" measurement?

Now that is a good call! I will decap separately and see what I get. Thanks

 

[duanepa]

Other ideas are good too. Half a thou. isn't much. Brass hardness varies but not too much on second firing. Slathering heavily with lube can cause it also. DW

 

[RonAKA]

Fitter, what method are you using to short stroke your press? Does it cam over or come to a stop. The stop type may be a bit more consistent if it is a solid stop. The best method probably is to use an over sized shell holder like Redding sells (for a ridiculous price). But even they may need some customization as they only sell them in 0.002" increments. Another approach may be to have a standard shell holder milled down where the head of the case sits, if it is only a thou or two. I think the most positive way to get consistent result is to have the shell holder contact the die to a hard stop.

Redding Competition Shell Holders