MPA Rim Variance

[MI2600]

I've been converting some 5.56 to 7.63X25 and in another thread noted the flash holes off-centered in a lot of "MPA" brass.
After cutting, reforming, and trimming, I finally got to reaming the neck insides with my Forester trimmer. Out of 80 cases I found 8 MPA pieces of brass that had rims up to .013" larger than the others. As a result, the collet would not hold the brass.
Is this a normal variance? Wouldn't that cause problems in 5.56 weapons?

 

[rcmodel]

Yes, maybe.
But maybe not?

It could be case head expansion to fit the bolt face on the first firing?
Or it could be the weapon they were fired in was far enough out of spec to work anyway?

But regardless, if it is that much larger?
I would not use it!

rc

 

[MI2600]

I don't know what the original weapon was...probably just range brass pick-ups.

Good advice. They are in my junk brass bag.