New Banana shaped brass

[mtang45]

I just bought some Remington brass for my 300 RUM and conducted some quality checks. When I placed them on my concentricity guage I found a significant percentage of them were warped from base to neck, like a banana.

Anyone ever seen this before? Will it straighten out with FL sizing?

 

[Minesweeper3433]

I would first contact the maker of that brass about this particular problem as it sounds pretty bad. I would think straightening it out in the die would cause thin spots to form were the brass had to get stretched to straighten it. Makes me imagine fast case failure.

 

[fdshuster]

mtang45: No, they will not straighten with sizing. Fire them one time & check them again. They could straighten when fired, or at least not be as poor as they are now.

This is typical of defective brass from the time it was drawn. If you have a tubing micrometer, measure the case neck walls & I'll bet you'll find differences of as much as .005". I've seen Remington brass that has these differences so obvious that you can see one side of the case mouth tissue paper thin & 180 degrees around the circumference it will be very thick.

This difference in brass wall thickness will extend from the case mouth all the way down to the base & the main reason for the banana shape.

I've checked loaded Remington factory ammo (.223) with my Sinclair coincintricity gauge & had runouts of as much as .012". Spin the round under the dial indicator & it's moving left & right like the windshield wiper on your car.

And some claim factory ammo is better than carefully made handloads?

I've always had good luck with Winchester brass when Lapua is not available.

 

[TheSnake]

Good info FD. I guess I should be checking for this on new lesser expensive brass. I've got the tools, I just never thought to check for this. Good post.