What is this case I found?

[some_kid6]

Went shooting and found this while going through my brass. Any ideas as to what it is? It looks like a shortened 5.56 round (1st pic is next to 5.56).

 

[Walkabout Dan]

Some 22 wildcat formed from 556 cases.

 

[303hunter]

Was gonna guess 5.45x39 until I saw the LC headstamp.

 

[GymB]

221 fireball

 

[ronn47]

221 fireball

I don't think so, 221 Fireball case is 1.40".
I checked several others I could think of, so I guessing a wildcat of some type.

 

[Snoopz]

221 fireball

Was thinking that but nope, got one... case length 1.400 in
then 222 Rem, or 222 Rem mag...nope

1.552 mic'd length throws it off..Don't have my Herters Book handy
what ever it is the primers look ...well

close to 5.45x39 length

-Snoopz

 

[Toprudder]

Some 22 wildcat formed from 556 cases.

I agree. The LC Nato headstamp is s 5.56 case.

Perhaps this link will help:

https://firearmwiki.com/wiki/List_of_AR_platform_cartridges

 

[1075tech]

Found a reference to a 25x40. apparently made from 5.56 cases. Can't seem to find a picture though.

 

[scratchmark]

Maybe still a 222 as the brass will stretch upon Firing.check shoulder specs

 

[nbkky71]

I would have guessed 20 or 22 Nosler but I think the OAL is too long on the case