New brass expansion

[outlawjw]

I loaded a ladder test for a 7mm REM mag for a tikka t3 rifle once I shot the whole test ( I didn't experience any signs of over pressure ) , I measured the brass 1/8" below the mag ring for lack of the proper name . It was .007" bigger than when new . All of the brass was bigger , I put this down as the shape of my chamber . I started with 65 gr of retumbo up to 71.2 grs which is compressed in Hornady brass. Is this much expansion normal.

 

[243winxb]

The actual measurementS, before and after would help. How do they compare to SAAMI. http://saami.org/specifications_and_information/index.cfm

 

[Bart B.]

Yes, it's normal.

Chamber diameter will be .001" or more larger at that point. Case bodies shrink back a bit.

 

[243winxb]

http://www.larrywillis.com/ Belted Magnum Collet Resizing Die .
Good reading on the website.

 

[Sunray]

The 'mag ring' is called a belt. As in Belted Magnum. Assuming we're talking about the same part of the case. The case measured .511" right at the belt and tapers to .490" when new. It expanding and staying a 7 thou more isn't something to worry about.
"...71.2 grs which is compressed in Hornady brass..." The brand of brass makes no difference, but 69.5 grain of Retumbo is compressed. All Max loads of Retumbo are compressed. Compressing starts long before you're even close to Max. Compressed loads are nothing to worry about anyway.

 

[Bart B.]

Compressed loads are nothing to worry about anyway.

They are when powder particulates physically break and change their burn rate.

 

[old heeler]

I loaded a ladder test for a 7mm REM mag for a tikka t3 rifle once I shot the whole test ( I didn't experience any signs of over pressure ) , I measured the brass 1/8" below the mag ring for lack of the proper name . It was .007" bigger than when new . All of the brass was bigger , I put this down as the shape of my chamber . I started with 65 gr of retumbo up to 71.2 grs which is compressed in Hornady brass. Is this much expansion normal.

Your reloading die isn't going to size just above the belt. With repeated firing that dia is going to get bigger and mag headspace off the belt. This pretty much explain it.

http://www.larrywillis.com/headspace.html

You can do search on it also.

 

[outlawjw]

I've been without service a few days . Thanks guys , some shot in my other rifle measure the same as the expanded ones , & some I loaded that were once fired also measure bigger than new by .007". Boy if I had half the knowledge that you guys have already forgotten , I'd be in good shape , but I don't remember like I used to . Thanks again & I did read all directives good stuff.

 

[ants]

I measured factory ammo and new factory brass over the last 60 years.
The body of brand new brass (many brands) is often slightly smaller diameter than SAAMI standard.
I guess the manufacturers want to make sure it slides in and out of a tight chamber cut to SAAMI minimum.

 

[outlawjw]

You are probably right