7.62x51 internal neck diameter ?


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SteveW-II
January 1, 2009, 09:53 AM
I just bought 1000 pieces of processed ex military 7.62 brass from 'Top Brass'. Very nice it is too.. Cleaned (even the primer pocket), trimmed and resized.

However, I just put an internal mic on the neck, to measure the diameter to get an idea of neck tension. Average of 10 pieces gives me .302".

I think that's tight. I feel pretty sure that I am going to get jacket material shaving off the bullets as I load them. Performing a survey of all the (308) dies I have (Lee, Redding, RCBS) they all leave the neck internal diameter of sized brass at between .305 to .306 .

While I realise that a good grip on the bullet is very necessary for semi auto 7.62's, .302 just seems waaay too tight.

Has anyone any experience of loading 7.62 with such tight necks ? Anyone agree that .302 is too tight, or am I just getting my panties in a wad about nothing ?

FWIW, my 'cure' would be to use a Lee collet die, screwed half way in to the press to expand just the necks (the brass wouldn't reach the collet) as part of the progressive reloading sequence.

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Oddbod
January 1, 2009, 10:17 AM
.302" does indeed sound tight.
I just checked a dozen or so cases I resized using a Lee die & they're all between .304 & .305"
Check the neck is chamfered in case there's a burr on the inside & then try seating a bullet

NuJudge
January 1, 2009, 11:10 AM
Check your measuring tool against a known quantity. My modern measuring tools are nowhere near as repeatable as my old-fashioned vernier caliper.

That said, .302" does sound too tight. Some kind of "M" die or expander would seem to be in order.

Walkalong
January 1, 2009, 11:45 AM
It may or may not be a bit tight, but it will not shave material if the case mouth has been chamfered, especially with boattail bullets.

Try running one through your sizer and see if the expander ball opens it any more. If it does, and you like that measurement better, it would be easy enough to put that expander rod on a die that won't touch the .308 case and run it through all the brass.

USSR
January 1, 2009, 12:28 PM
Top Brass probably ran them thru a SB die without an expander ball. If you feel it is too tight, then just run them up in your die just enough for the expander ball to open them up as Walkalong suggested.

Don

rcmodel
January 1, 2009, 01:41 PM
+1

Sounds like no expander ball was used at all, so you will have to do it yourself.

rcmodel

SteveW-II
January 1, 2009, 02:40 PM
Sounds about right. So, as I place each peice of brass into the loader, so I will dip the neck in Mica and the first station will have a sizer die just about screwed in enough for the inside of the neck to be sized on the sizer ball.

Thanks !

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