Excessive Headspace?

[ElkHunter]

I have a 6mm Rem built on a Mauser 98. It's a beautiful rifle that was my grandfather's so i don't now much about its usage, other than it was built 50+ years ago.

I have reloaded several loads with various powders (not close to max), bullets and seating depths only to get 3-4" groups and sometimes they open up to 6". Primers are flattend, lots of soot on the neck and bad groups. Also, I have had some cases of once fired brass crack about 3/16" above the web. Is this an indication of a headspace issue? If so, what causes it and how easily is this situation corrected? thanks.

 

[clearwater]

Headspace is where I would start. Check the gun or the fired, unsized brass
with a gauge. Then check the resized brass with a gauge to see if you are
oversizing.

The primers and sooty necks may be another issue.

 

[Guest]

The cracking above the case web indicates a headspace or sizing issue. It could be a max spec chamber and you're sizing down all the way to minimum spec, and stretching the cases with each firing. The flattened look of the primers also indicates this - I bet the decapped primers have a noticeable bit of the anvil sticking up above the cup, don't they?

How many times has this brass been loaded and fired?

I'd suggest a good gunsmith check the headspace, and then you invest in a neck die or search for one of the threads on partial full length resizing here on the board and quit sizing all the way to the base and pushing the shoulder back to minimum spec.

 

[Ridge_Runner]

Try this, poke a 257 expander ball down in a case, then screw you 6mm fl sizer up a ways and start sizing it, try it in the gun every time, keep screwing the die down and resizing the same case until the bolt goes down with just a bit of resistance, then screw the die down another 1/8th turn and lock it down, now try your cases see if you still have flattened primers and insipient head separation, if so your need a gun doc.
RR