JimTom wrote:For those that are interested I did manage to successfully convert the .222 brass into 300AAC. I learned a few things along the way, and now have a pretty good supply of brass for the blackout.
After cutting the brass with an angle grinder, I then annealed the brass as I found I had about 1 in 5 split when expanding if I didn’t anneal.
Next they went through an interim expander die, then through the 300AAC full length die.
Of course then the cases were trimmed to size, champfer and deburred.
Have loaded and fired a few now and have had no issues whatsoever.
In saying that I can now see why most people just convert .223 brass as it would be a far easier process. Still it was a good learning experience and I know have a healthy supply of expendable brass.
JT you inspired me to also try forming my own from 223. I bought a 1.5kg bag of once-fired, mixed hs 223 brass from a popular online store for $40 delivered - about 150 cases, which I thought I was very reasonable. It's a mixture of ADI, OSA, Hornady, Federal, Remington, Winchester, Lapua and a few other odds and ends.
I also bought a tiny dropsaw for $70 from online which functions just fine.
I anneal using a butane torch and a rotating tray of water.
An observation I've made is the brass varied a bit when it came to thickness, which was problematic with regard to headspacing. Using my Lee die, i just wasn't getting the headspace clearance I needed (i.e. the lugs were very tight to lock up).
So I bought an RCBS die which did help, but ultimately did not solve the problem. I did some more research (thanks to sungazer's tip into "shoulder bumping") and found out some ground a shell holder thinner to allow the die to drop just that tad lower.
I ground off 15thou from the shell holder, which allows for the bumping of the shoulder back just a fraction more, thus allowing all brands of brass (except Sako and Tikka) to lock up without any resistance. Neck turning is a consideration, but once fireformed, I'm a big fan of the Lee collet die which is supposed to stop runout - especially if you size three times per shell with a 120° index.
Working with the small-shouldered 300aac cartridge is really really easy - it's almost like working pistol brass. You need only the tiniest amount of lube on the shoulder to FL resize.
I've also been seating the Speer 125gr TNT pill out to 2.1" OAL because I saw a knowledgeable dude do it youtube. This is allowing me to comfortably fit in 18.4gr of 2205, and get that a bit closer to the lands. Generally, I feel a longer OAL feeds better in the RARR.