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Dromia, you have a way with words that always makes me smile. Thank you.

O rings do as you say but really are an unnecessary faff on especially as the OP intends to neck resize after fire forming for his gun.

I see this case head separation propensity for 303 written often, I must have shot tens of thousands of 303 rounds over the years and have never had it happen to me yet, famous last words. Where I have seen it happen has been with old poor quality military rounds and with hand loaded rounds that have seen too many firings.

HXP is usually excellent brass and I suspect that the OPs issue is a function of the expander ball and the previous brass owner miscounting somewhat.

Also have you checked the diameter of the replacement expander to make sure it is for the right calibre, either way get rid of the damned thing.

WelshShooter wrote:Dromia, you have a way with words that always makes me smile. Thank you.

Thank you, it is just a function of striving to keep the Tourette's at bay.

dromia wrote:O rings do as you say but really are an unnecessary faff on especially as the OP intends to neck resize after fire forming for his gun.

I see this case head separation propensity for 303 written often, I must have shot tens of thousands of 303 rounds over the years and have never had it happen to me yet, famous last words. Where I have seen it happen has been with old poor quality military rounds and with hand loaded rounds that have seen too many firings.

HXP is usually excellent brass and I suspect that the OPs issue is a function of the expander ball and the previous brass owner miscounting somewhat.

Also have you checked the diameter of the replacement expander to make sure it is for the right calibre, either way get rid of the damned thing.

I have had case-head separation happen to me using Sellior & Bellot brass (fire formed from factory loading, neck sized twice subsequently), but it's common knowledge that S&B brass is brittle with .303. I use Privi brass which works great. I suspect you have just used good quality brass.

EDIT: I wanted to stress that my .303 loadings are nominal and are not max loadings.

I have had good case life from S&B brass. Kynoch use or used to use S&B brass and I had a few thousand rounds of the stuff, however it is thin brass, like Winchester. I am more attentive in the annealing department with thin brass and usually anneal after first firing ad then every two or three firings afterwards as thin brass seems to work harden sooner and more.

For starters HXP, .303 brass is about as good as it gets for quality (PPU is nearly as good)

I will however, take issue with the Lee expander buttons in the F/L sizing die.

I load 16 calibres, all with Lee dies and have never had a problem, I use Lee case lube for all non-carbide dies both outside and in the neck.

Properly lubricated, the expander button is not an issue, I would suspect that the lube used and/or case length could be an issue here.
As previously posted, maximum case length for .303 brass is 2.222 and the ideal trim length should be around 2.212.

ukrifleman.

If the head stamp is 76 then bin the lot. Once fired 76 HXP were given to me & I had separating issues with that date they went to scrap. I have reloaded HXP 75 83 85 F/L sizing them no problem all using the same Lee die set. I now neck size them.

That is interesting I have 76 HXP brass that is as good as any other year but the OP could well have the same bad batch as you.

Lubing the inside of the case neck will ease the expander abomination somewhat and reduce the neck stretching somewhat however on the down side you then have lube in the case neck that needs removing, consistent bullet to case neck tension is crucial for consistent ammunition and lubes inside case necks won't give you that.

The M style dies can be had in in differing sizes from various sources to ensure a good consistent fit for both bullet and brass, and is a far easier step than removing the lube from the inside of the case neck.