Factory 308 Norma - usually hot?

[rimfiremac]

Just ran some factory 180gr Oryx thru my 308 Norma and the magnetospeed claimed speeds over 3300fps. No heavy bolt, swipes or craters resulting either.

Hand loads with 7828 were exactly as anticipated for speeds during the same session. So while it could be 'instrument error', both the data and style of error (fast as opposed to slow) doesn't seem to jive to support that.

I'm curious if anyone has crono'd their 308 Norma (not 300, the original classic 308 mag) and found speeds to be surprising.

 

[MagnumManiac]

There has to be an anomaly with those velocities, no way you are getting above 3300fps from a 180g bullet.
That is beyond RUM velocity.
I ran a 300-338WM and 3000-3100fps with 180's was absolute maximum, most powders produced less than 3000fps.
I had a 23" barrel.

Cheers.

 

[cohunt]

Norma claims 2960 fps. For that ammo, if you are pushing 3300 I'd let them know as you might have some bad ammo

 

[can1010]

there would be serious pressure at those velocities that a blind man could see. it is some sort of error in the magnetospeed or possibly not a 180gr bullet, maybe mismarked and is actually only 150gr.

 

[rimfiremac]

It's a mid 90s or earlier production lot, just for clarity and ease of concern with recent production.

I'll pull a few and weigh; if they're actually 150 gr, that would make much more sense - that's a very good thought

 

[Shane Lindsey]

How does the brass look. I would think you would need a mallet to get the bolt open.

 

[rimfiremac]

Bolt had no issues at all and brass no signs of issue, which was counter to my expectation seeing the speeds

What makes the most sense is that they're 150's in a 180's marked box. It'll be a while till I get a minute to take a look at it, but that's probably the most likely explanation**

**for the tldr's, it's a vintage production box