Back in the early 70's, I bought a beautiful (used) custom rifle:
Sako L461 single shot action, Douglas 22" bbl, Claro walnut Monte Carlo with flat forend (for bench work), topped with a Weaver K-6.

Anyway, it's a Wildcat based on the .222 Rem Mag. with the shoulder pushed back to .222 Rem location resulting in a long necked case similar in capacity to a .223. Custom in-line hand dies came with it.

I've always used IMR 3031 and CCI primers...it shoots like a dream.

That's all...just wanted to post what I had.

Can you post pictures? Sounds interesting and I'd like to see it!

Rrgeezer: What an interesting "wildcat" you have there. I am an internal ballistics idiot so to speak and I was wondering if you know what the originator of that cartridge was trying to accomplish?
Were they trying to increase the rounds accuracy somehow with the long neck (and yours shoots so well maybe that was accomplished!) or diminish the velocity for some reason?
Those Sako single shot actions were the neatest things. I had a chance to buy a bunch of them way back when and kick myself for not doing so!
Live and learn!
I have had very good to excellent accuracy with the 222 Remington Magnums that I own and have owned and was just curious as to why the effort was went to, to diminish the body and lengthen the neck.
Thanks in advance for any info.
Hold into the wind
VarmintGuy

This sounds like one that I made based on the 222 Mg. brass and sized in the 223 dies.

The result is a 223 with a neck about 1/10" longer than the standard .223.

It was not necessary to cut the throat deeper because the .223 is usually long in the throat anyway, so all I had to do was ream the neck of the chamber thet 1/10" deeper.

What I wanted was a .223 with a longer neck so I could seat lighter bullets out to touch the rifling. Also, I like a longer neck because even longer bullets can be seated deeper for a better bullet pull even while being seated to touch the origin of the rifling.

So far, it seems to shoot significently better that it did with the standard length neck.