Blackout sizing issue

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Paddy

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My foray into 300 blackout has led me to sizing cases with a redding pro carbide die set, and I'm having terrible getting finished rounds to chamber consistently and also fitting the case gauge. I started at touching the shell holder plus half a turn, and advanced it to 3/4 turn but that feels like a lot of cam-over and didn't really help size them more. I also started doing an"double tap" on cases being formed from used 223 brass, and that helped, but still missing something. What should I try before grinding down my shell holder .010?
 
Have you tried a smoked case to see where its rubbing? Clean dies? Chamber to spec? Brand of brass? Your decapper / expander set right? Lubed case and inside of neck?

I have converted thousands and thousands 300blk cases from 5.56 and found a process that works very well for me. Basically I pull the decapper from the sizing die and size the full 223 case, then cut and expand the neck with an expanding die. That process works well for me and I have never had a piece of 300 not chamber in several AR's
 
What part of the case isn't fitting the case gauge? I've found lots of variation in the wall thickness of .223/5.56 cases from various manufacturers. This results in lots of variation in neck outside diameter of the finished 300 blk cases.

If neck outside diameter is indeed the limitation, then either 1) stick with headstamps that don't have thick walls, or 2) ream the necks of the oversized cases and resize.

I've chosen to stick with Lake City brass for conversion to 300 blk, and leave my thick walled stuff for .223/5.56 reloading.
 
I originally had issues with my Lee C312-155 bullets not having the right Ogive and getting hung up on the rifling.

Make a dummy and sharpie it (poor mans dykem) chamber it and see whats up.
 
Consistent and enough lube on the cases and inside the neck. Makes a difference with my Hornady and RCBS sizing die. Enough lube and shoulders are consistent and slightly dry and shoulders are left a thousandth or two longer. I roll my cases on a pad. May not be your problem? As mentioned, some brands may have too thick necks. Necks should be less than .334"
 
Do sized cases fit the gauge and chamber OK? What diameter are the necks when loaded? How exactly do they not "fit" the gauge?
 
I'm having a problem where my bullet is causing the round to stick in the chamber. I have them loaded almost below the minimum COAL and it's still hard to extract them. An empty case comes out with no issues. Think I have a burr in my chamber as the Sharpie'd bullets end up with a scar on them. I don't think it's from feeding.
 
Im not totally sure where the interference is. I sharpied a round and it might be too thick neck in some cases, Hard to read the scratches, the sheridan gauge is very well machined! My 147gr surplus pulled bullets are also catching the gauge and possibly the chamber too. I didnt measure them, I should do that.
Sizing with the expander out caused the neck to be very undersize which I thought to be normal since they are changing dimension so much being formed off a 223 case. Oh, maybe I should've mentioned that in the initial post, these are not factory cases, but range fodder trail mix 223.

There seems to be one headstamp, GECO that will not size no matter what. Also PPU was tough, but a triple tap seemed to budge most of them down. Maybe a polish on my expander ball would be prudent? Harder crimp with Lee FCD?
 
sounds like it could be your bullets, if they are pulled they could be out of round. When you pull your expander you still need to expand the necks somehow, I just do it in two separate steps. What does your expander measure? Also, what is your trim length?
 
300 AAC Blackout - Maximum neck Diameter

I sharpied a round and it might be too thick neck in some cases,
Click to expand...
SAAMI's maximum neck diameter of a loaded round is .3340" http://www.saami.org/PubResources/CC_Drawings/Rifle/300%20AAC%20Blackout.pdf From Lee on case forming.
Case forming dies usually need to be made to smaller internal dimensions to compensate for more spring back, because the case dimensions are being altered to a greater degree. Sometimes a full length sizing die will work as a case forming die, but it depends on a large number of variables, and is impossible to predict with any accuracy.
Click to expand...
This means a standard FL die may not push the shoulder back far enough for the round to chamber. May even happen when sizing 308 GI brass to 243 win.
 
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Okay my expander button measure .307, and bullets seem fairly round, and .309. The neck diameter on a finished round of a LC brass is .334, however the PPU neck has measured .337, so that means PPU is thicker brass? Which makes it harder to size, more spring back and wrong neck diameter?

So if a different die is used to form cases from 223 what is that even called? Is that a custom made die? Small base die? Or grind a die mouth down and keep it just for forming purposes?
 
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Walkalong made a chamber cast of his rifle. Chamber may run larger or smaller, same as dies. I would go with the SAAMI standard maximum and discard your loaded rounds that have necks at .337" The brass is to thick in the neck area, you are correct. If rounds still do not chamber in your rifle, remove metal from the shell holder. See where fired brass sits in the gage first.
 
^^^
What he said about thicker necks and lubing the inside real well

Here is my process for forming 300blk brass from 223 case

Rough size with standard Hornady 300blk die with expander removed
cut on mini chop saw
anneal
SS clean (this removes any burrs from the chop saw)
expand the neck with a 21 century expander
trim to final length / chamfer / deburr with Giraud trimmer

As far as I know there is no special die for forming from 223 cases, just removing the expander from a standard 300blk FL sizing die
 
however the PPU neck has measured .337, so that means PPU is thicker brass? Which makes it harder to size, more spring back and wrong neck diameter?
Click to expand...

SAMMI spec for the neck of the chamber is .335 +.002/-.000

.337 can be too big a chamber cut to spec. It definitely seems like it is for yours.

Yes, thicker brass, which does not necessarily size tougher. Spring back is determined by the hardness/toughness/degree of work hardening. And yes, it is on the high end of spec for diameter. Too big.

http://www.thehighroad.org/showthread.php?t=710664
 
Funny how I didn't know how dark the room was until you guys started turning on lights. That makes tons of sense although I'm curious why saami would spec the chamber so tight when the blackout was born of the idea of using 5.56 brass. Maybe the intent was 223 as the brass is thinner? (I've only heard this never measured).

I will say the 223 stamped cases did seem to take the new form better than much of the 5.56
 
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