Thread: New 223

Being the Internet I know I’ll get the normal question and comments; “why not a 223AI, 22-250, 22-250AI etc”, but I figured it was more about me trying to learn a bit about this reloading.

Like a number of Rem700 Short Actions. My 223 has had a few issues feeding. Couple of way to help the situation; new Mag spring and follower, or change to a longer case!!!

I spoke to Robbie at Gunworks and we came up with a plan of attack, make the case 7mm longer and ream the chamber to allow for this. I understand there is a Thompson Contender in NZ with this done, and maybe a few others around.

So I grab a handful of 5.56x45 M200A1 cases that have never been crimped (or similar, ensuring there total length is over 55mm).


The idea is to neck this up to around 7mm or .270 and then reform a 223Rem shoulder and neck 7mm further out than a 223Rem and then fire form the rest to fit the modified chamber.

This is the first project I’ve needed make such significant changes to a case, it was an interesting learning curve! I crushed the first 9 case and then managed to get the next 3 sorted , after this I was away.
This is how it goes:
1. Anneal the cases
2. Apply plenty of case lube to the inside of the neck
3. Running the M200A1 through my Lee 223Rem F/L die pulls the long neck out(using Lee dies as they have a long tapered internal shaft)
4. Ensure there is case lube inside the neck again
5. Run them through a Lee 270WSM dies(using this as it what I already have and the length is ideal)
6. Place a 7mm spacer on the Shell Holder and run through the 223Rem die again
At this point I have a case ready for fire forming in the rifle.

Cases I destroyed in the process:


Ready for Fire Forming - I can now correctly form cases without wrecking any:


Fire Forming
After trying a few case with a 53gr V-max bullet and 25gr of BM2, I found I really need to hit it a bit harder. Stepping up 0.5gr at a time, 25.5gr still has rounded shoulders, found the 26 – 26.5 was ideal and 27.5gr was bad!


Here we have a 223rem, the Parent Case, Ready for fire forming and the end result


This is the end result:


Load Development
Ultimately I want to be somewhere between a 223AI and 22-250 (closer to 22-250 would be nice).
With only a handful of case read to go I loaded them up with 27, 28, 29 and 30gr of BM2. Speed of the 30gr load was 3550fps, but the primer was getting worked pretty hard. Need a slower burn powder as I have a case capacity of around 36gr and for this to be worth the time and I want it to go fast!

I want to run a heavier bullet too, somewhere around 65-70gr. Barrel twist is 1:12, so I might have some limitations here too.

I’ll update again on load development and case life shortly.