How much case head expansion on Norma 300WSM brass.

[RDavies]

A freind has shown me some cases out of his new 300WSM with Norma brass. With a fairly moderate load compared to what others are running (cant remember load but it is H4831SC with 190gn pills), he is getting .001" case head expansion. Is the Norma 300WSM brass known to be soft, or is .001" case head expansion normal on this case?
I have always limited loads to .0005" but only shoot a 284.

 

[RDavies]

Also, he is using a custom action (BAT I think) with 120 shots through the custom 10" twist barrel.

 

[Larryh128]

I just miced a Norma 300 wsm new & a once fired stiff but not hot load. Both miced the same. .5525.

 

[RDavies]

My freinds cases measured .552 before firing and .553 after firing, so I would say he has either very soft brass or a tight barrel.

 

[NeilNE]

I would check chamber also, to see what size it is. I use 300WSM necked down to 7mm and have had no problems with it. I have three guns chamber for it that I used in 1K BR.

 

[RJ338]

Neil is right on with the question of how big the chamber is. If the chambering reamer wasn't held in a floating holder, ie. center in tailstock not concentric with the bore, it will cut oversize at rear of chamber(and not concentric in the throat).
Most PTG reamers I have used are pretty snug in that dimension.

 

[mikecr]

My freinds cases measured .552 before firing and .553 after firing, so I would say he has either very soft brass or a tight barrel.

You said you have personally "limited loads to .0005"
Does your example here represent that? Was his brass measuring .5525?

When finding MY max load, I expect that my webs will grow and settle ~1thou. Then at some point working up in charges, I'll see another .0005" growth. This is where I stop, log it, & backoff, as it represents the point where body sizing will be needed on every reload.
I use Win, Lapua, and Norma. Haven't seen a bit of difference between them in this regard. This extra half thou typically occurs ~58Kpsi according to Quickload, which is near SAAMI MAX for most cartridges.

 

[RDavies]

Mike. I usualy try to limit my own case pressures to .0005" growth for each shot.
When my freind brought the cases around, they had already been fired and had 1 thou expansion compared to his unfired cases. I dont know the size of his chamber, but I measured it just ahead of the extractor groove and his FLS die doesnt size things down excessively.

His primers dont seem to show as much pressure sign as my medium load 284 and 308 primers, but his expansion is more than mine and some loads are getting ejector pin hole smears on the base.

After one firing he tells me some cases are now getting stuck in the bolt recess though the bolt is easy to open.

I have searched around a bit and some others reported soft Norma brass a year or two ago, maybe he got one of those lots.

 

[Larryh128]

Could be a lot of things but it really sounds like a large chamber.

 

[RDavies]

He has just measured some Winchester brass he was using for running in. After 2 light loads and one firing with the same max load as his Norma brass, the Winchester brass expands .0005" and shows no ejector mark at all.

But then the Win brass holds 3 grain of water more than the Norma so the pressure was lower.

The Norma brass is much heavier than Winchester brass, 228gns VS 244 gns.

 

[lynn]

CR500
I have been using Norma 300 WSM brass and recently bought some older brass in unopened boxes.
There is a big difference in the two brasses.
I am using 64.4 grains of H4350 with the 190 Sierras or 187 BIB's.200 pieces of my brass work great and the others won't hold the flat-based bullet at all even with 0.005 neck tension.Once they are fired once they will hold a flat based bullet but no joy on virgin brass.
Lynn