300 BLK sizing help! Some cases won’t size correctly

[nikdanja]

I finally got my cases today and they are already formed/processed. I went through to use my gauge to see if I need to resize any brass and 3 out of 10 need to be resized. Not that big of a deal.

I set my dies up and some cases are sized and fit great in my gauge AND barrel. Then there’s some cases that I sized but still don’t fit in my gauge AND barrel! I properly set my dies in my press but still don’t know what the deal is.

I’m using a hornady gauge and Lee dies. I’m also using imperial die wax for lube. Mixed head-stamp of already processed 300BLK brass.



Any ideas?

 

[Graye2]

What do the cases measure pre and post resizing (or before for that matter)? Given they are mixed brass when you run them through a die they will likely come out to different measurements given they were likely shot out of different rifles. You may need to turn your die down a little more to size them all or sort them between those that fit and do not and size those that won’t.

After you fire them all in your rifle they will fire form and be closer to the same on the second resize.

 

[J McGriddle]

Are you using a small base die? I recommend them for 300 BLK.

 

[nikdanja]

Are you using a small base die? I recommend them for 300 BLK.

I’m using a 223 shell plate on a 650. It’s almost like the case is to big for the guage and my barrel. The ones giving me problems are all the same head stamp also. Really hope all these cases arnt trash due to this issue

 

[mr45acp2u]

Mixed brass, is there any correlation to the ones that don’t size correct. Some brass isn’t considered optimal for conversion due to inconsistent brass thickness.

 

[Doom]

Try putting the head of the case in the gauge. If the rim fits, then the bottom portion of the case is blown out. Typically require a small base die to correct. Just turning the die down more will increase headspace and create other problems.

If the rim won’t fit, I’d trash that case.

 

[J McGriddle]

I’m using a 223 shell plate on a 650. It’s almost like the case is to big for the guage and my barrel. The ones giving me problems are all the same head stamp also. Really hope all these cases arnt trash due to this issue

Small base has nothing to do with the shellplate. If you use brass from another rifle, especially range brass, you need a small base die. The cases aren't trashed, just need a small base die.

 

[nikdanja]

Small base has nothing to do with the shellplate. If you use brass from another rifle, especially range brass, you need a small base die. The cases aren't trashed, just need a small base die.

Thanks for the suggestion. RCBS dies came in and fixed the issue!