shoulder bumping ?

I run a few pieces of 223 brass through my sizing die and it actually came out one or two thousands longer. The die is screwed all the way down to the shell holder. What am I doing wrong and how can I fix it to bump back two thousands ?

 

You die isn't contacting the shoulder, thus the sizing action is making the case datum to case head longer.

You don't say how you set your die up. If you screwed it down until it contacted the shell holder, lower the ram and start adjusting die down in small increments. If you already have done that, you may have to take a few 0.001"s off the top of the shell holder. You could take material off the die, but the hardening makes that more difficult.

 

The shoulder may be longer due to making the case thinner. Are you camming over already?

 

No I am not camming over, I am loading on a progressive press

 

Do they chamber? What gun?

 

Maybe something like Redding's Competition Shellholder Set might help:

https://www.redding-reloading.com/online-catalog/35-competition-shellholder-sets

 

Which is likely not low enough. You need to feel a distinct cam-over; the press handle should pop into a detent at the top of the stroke as the frame flexes just slightly. It will them pop back out on lowering.

Yes, this applies to progressives too.

 

Chamber one of your resized cases. If it.chambers easily its not time to set up a shoulder bump.

 

it is a Tikka T3x in 223 and yes the cases all chanber easily but are longer average 1.766 not 1.750

 

Correct me if I'm wrong, but it appears you are measuring overall case length. Cases will usually get longer each time you fire them. Bumping refers to the shoulder. When cases get hard to chamber it's time to bump.

 

How many times has the brass been fired?

If my die is in full contact to the shell holder ( I use a feeler gage to measure in thousand btw) and my case is growing I must not be fully fire formed (yet), as mentioned by others if my case chambers freely I must not be in need of a shoulder bump (yet) about 3x fired depending on how hard I hit them does it for my rifle.
For a SAMMI chamber, I drop the fired case into a Wilson case gage to determine when to bump, I could also use a field gage or a Sheridan gage.
On my 6 Br I have the reamer print.
J

 

All presses have some amount of spring in them. Run a case into the die and look for a gap on top of the shell holder. The die may need to be adjusted down a bit more. I've never used a progressive press so I can't advise you of any potential problems that could arise.

 

It’s entirely possible that your shoulder moved forward, instead of pushing back, after sizing. This happens when your sizer die isn’t screwed down enough, and the shoulder portion of the die isn’t making contact with your brass. You are squeezing the body of the cartridge down, and the brass has to go somewhere, so it pushes the shoulder forward. As a past responder stated, you may have to grind some material off the top of your shell holder. I have found many sizing dies that were drilled too deep, and I needed to modify the shell holder to allow proper shoulder bump.

 

I think there is some confusion on wording or measurements . Bumping generally refers to the shoulder movement but the numbers you give are clearly for total case length ( head to case mouth ) and not shoulder bump ( head to datum point on the shoulder ) . Which are you referring to because there are different answers to each ?

Or are you saying when you bump your shoulders .002 the cases grow .016 ?

 

If they chamber easily, then just trim them. I usually have to trim after FL sizing. You don't want to push the should back farther if they chamber easily -- you could create excessive headspace..

 

Trim them and look up shoulder datum measures

 

What I meant to say was that when I try to bump the shoulder it actually didn't bump at all, it did got one thousands out further. when I said the cases are 1.766 I am referring to the oal from case head to case mouth. I understood they need to be 1.750. OAL and bump two different things.

 

You only bump the shoulder, you trim for oal.

 

When you full length resize you are squeezing the case smaller in diameter and near the end of sizing you are also pushing the shoulder back. This squeezing action inside the die makes the brass flow upward in the die and makes the case longer. If the die is not adjusted down far enough the shoulder is not pushed back far enough and the case may not chamber. And the OAL of the case increases each time the case is sized and eventually needs to be trimmed.

Look at the image below and the effects of full length resizing and what happens to the case inside the die.

 

New brass or fired brass? New brass may be short so it will actually grow. you need to compare fired brass to sized brass.

If your fired brass is growing, you chamber may be short. You can machine a few thousandths off the bottom of the die and then you'll be able to adjust shoulder bump.

--Jery