Another 300aac question.

[Mbaker78]

For those of you that form your own from 223, when running them through the sizing die do you just run it through once before you trim it or do you run it through 2+ times?

I cut mine before it hits the sizing die so that I don't have to remove the expander rod, but when sizing I'll run it through a second time before it gets trimmed. Just curious as to whether this is an unneeded step or if it helps in the long run. I'd imagine that it would just help smooth out the shoulder, which is why I started doing it... But then again, my dad is a millwright and to him anything worth doing is worth overdoing. Maybe I picked up a bit of that habit after all ;)

[Van Ness300blkout]

I cut down my brass before I size as well. I only run the cut down brass through the sizing die once. I've done around 2,000+ rounds this way. If it makes you feel better or you see better results running them through the sizing die 2+ times go for it! I'm sure it won't hurt anything. But IMO it only needs to be done once.

[DaveL]

When I was forming 458 win brass into 416 Taylor brass there was an issue. When I ran the cases into the standard sizing die I was using, the shoulder was offset to the right. I would have to spin the cases 180 degrees and run them through the die again to get a concentric shoulder. But with the 300 blackout I didn't see any inconsistencies with the shoulder as long as I removed enough brass on the 223 case to completely remove the shoulder. I still run the cases into the die twice and spin the cases 180 degrees in-between the two sizings. The cases and shoulder on the blackout are so small that my old eyes aren’t sure if it's concentric or not. So, better safe than sorry. Bottom line? I will continue to run any case I am forming to another caliber through the sizing die twice, with a 180 degree spin just to be sure.
JMHO
Dave
I would add that I trim down the 223 cases with a bench mounted belt sander. It's WAY faster than my Lyman power trimmer and it heats up the case hot enough to require gloves so as not to burn my fingers. I then drop them in water to anneal them. I'm not sure if the cases get hot enough to truly anneal them or not but it can't hurt. I've had no neck splits with this procedure after numerous reloads.

[Mbaker78]

I did 200 of them last night and decided to try 5 each way just for comparison... The shoulder does look to be a little bit more formed on the twice struck brass than the single...

I haven't had any feed issues with them and really the only downside I could see would be that the brass work-hardens faster. But after they've been fired they only get run through the die once, and I'm looking to start annealing them in the future...

Oh well, I guess I'll keep on trucking the way I have been unless anyone has a very compelling argument for why I shouldnt...

Thanks for your input.

[Happyguy]

I cut them, run them through the Dillon 1200 and then run them through a 300 Blackout sizing die to remove the primer and expand the neck. David

[Mbaker78]

I can't afford a 1200 :(

I've found that my lyman bench mounted trimmer does very well when paired with a Milwaukee 18v drill though.

[oldsagerat]

I lube the .223 cases first with imperial sizing die wax. I run them
into a 300 BLK trim die once, cut the case off with a small chop
saw, trim the case to length on a normal case trimmer. Then
To test if the case neck is thick or thin, I lube the case, run it into
a 300 Blk sizing die. I then seat a .308 bullet and measure the
outside of the case neck with a micrometer. If this is thicker than
a factory round I know I must turn or ream the case necks before
I use them to load up 300 BLK. A tedious but necessary process.
Most 300 BLK formed from military .223 has necks that are too thick. They may chamber in your rifle but there won't be enough
room for the necks to safely expand on firing and this can be
very dangerous to you and your firearm. Just a little FYI.

[Mbaker78]

I've run nearly 600 rounds through my rifle. Haven't measured or turned a single neck, haven't had a single issue with it either... Most of the brass I use to make my AAC brass has been fired more than twice though.

[GRUMPA]

I lube the .223 cases first with imperial sizing die wax. I run them
into a 300 BLK trim die once, cut the case off with a small chop
saw, trim the case to length on a normal case trimmer. Then
To test if the case neck is thick or thin, I lube the case, run it into
a 300 Blk sizing die. I then seat a .308 bullet and measure the
outside of the case neck with a micrometer. If this is thicker than
a factory round I know I must turn or ream the case necks before
I use them to load up 300 BLK. A tedious but necessary process.
Most 300 BLK formed from military .223 has necks that are too thick. They may chamber in your rifle but there won't be enough
room for the necks to safely expand on firing and this can be
very dangerous to you and your firearm. Just a little FYI.

If a person sticks with known quality head stamped brass measuring the necks is a wasted step. Military brass isn't specific enough since the Military uses more than a single head stamped round. I know of a couple that are foreign that the Military uses that are to thick to convert into 300BO unless the extra step of reaming is done. Almost all domestic brass with a couple of exceptions are good for conversion. Most folks like the LC head stamped cases due to the fact a person can get them in quantity at a good price.

[oldsagerat]

Grumpa,

You are right. I was just encouraging caution. I have also seen
300 blk chambers with generous chamber dimensions that make
reaming necks generally unnecessary. I like 300 BLK, it's a fun
cartridge and a bit more useful than 30 carbine.

[Mbaker78]

The bulk of what I've converted so far is LC and FC with some WCC thrown in...