300BLK resizing?

[vanfunk]

Hi Guys:

So I literally just started reloading for 300BLK and am having a weird experience resizing cases with my Lee full length die. When I have the die set to factory standard, the case neck doesn’t look right. It’s more constricted than it should be for seating a bullet and shows a bulge too. Is this a bad die? Do I not have it set right? Brass is cleaned, mixed headstamp stuff from Diamond K brass.

 

[JmacD]

Zounds! Wrong thread! Oops

 

[JohnMc]

Deleted

 

[Walkalong]

How about a pic of the sized case with no bullet?

 

[Blue68f100]

Does the round fit the chamber?

It almost looks like the sizing die stopped short. A photo of a sized case would be easier to see.

Does sized brass fit your chamber?

Have you checked your brass length?

 

[JohnMc]

I just pulled my Lee die sized ones out and looked with a magnifying glass; they look good. I think Blue68f100 is on the right track, FWIW.

 

[mstreddy]

OP, what brass are you using? Is it factory 300 blk cases or converted 223/556? If so, which headstamps are you using? There are some brands of converted cases that have thicker brass and particularly at the neck they end up being too thick to work right for most.

 

[FROGO207]

If you are trying to roll crimp your bullet it looks like your seating die is messed up. Are your brass all the same length and under max length?

 

[vanfunk]

Thanks guys, I’ll get a full answer out to you tomorrow, but briefly here are some details:

Mixed headstamp .5.56 and 300BLK. Washed and polished from Diamond K brass.

I too am concerned that I might not have set the sizing die far enough down, but the resistance was so great (I lubed all the cases with One Shot) I backed the Die out a skosh.

Brass length is good.

Loaded rounds chamber fine in my Rosco barrel.

 

[W.E.G.]

Please get a CHAMBER GAGE for 300 Blackout.

You are only guessing unless you have proper tool for measuring.

 

[Walkalong]

Please get a CHAMBER GAGE for 300 Blackout.

You are only guessing unless you have proper tool for measuring.

I have one, but also did this with cerrosafe.

 

[jmorris]

Mixed headstamp .5.56 and 300BLK. Washed and polished from Diamond K brass.

I too am concerned that I might not have set the sizing die far enough down, but the resistance was so great (I lubed all the cases with One Shot) I backed the Die out a skosh.

FWIW I have a Lee 300 AAC die that will not correctly form a cut 223/5.56 case but will properly size one that has been formed in my GSI trim die.

If you are not sizing enough the BCG won't be flush or a sized case will be "sticky" coming back out. Looks like this.

Setting size die for AR type rifle.

www.youtube.com

 

[vanfunk]

Thanks guys. Embarrassingly I did not have a chamber gauge. I ordered one for delivery tomorrow. JMorris, I think you may be on to this; I suspect the condition you described is the whole or at least part of the problem.

Thanks again everyone!

 

[berettaprofessor]

For some brass, particularly cut down 223, I had to buy and use a small base RCBS die to resize 300BLK properly. I know Lee dies are supposed to be small-based sizers, but mine didn't seem to do that.

 

[kcofohio]

Most of the 300 BLK brass I have is repurposed 5.56 brass. As long as the brass neck wall thickness is .012" or less, they will fit the Lyman case gauge. I use the Lee's sizing die.

For a quick reference.

 

[vanfunk]

Thanks! None of my resized cases are passing, so something’s clearly wrong. That, and that the necks are too constricted to allow easy bullet seating, leads me to believe I have an out-of-spec die. I have another one coming today to try out.
Thanks again!