11mm '06 O'Connor?

Is the top round an 11mm’06 O’Connor Wildcat ? (bottom rd 7.62mmx51 for comparison) There is no headstamp and the head which is steel unscrews.

Case length is 68.56 mm / 2.699"
Bullet dia is 11.63mm / .458"

The case mouth is slightly belled out ( the bullet must be 2 dia’s ?)and the bullet is seated to a depth of approx 17mm from the case mouth.

Any info/help appreciated.


I have a little experience with O’Connor. About 20 years ago or so, I was at a Savannah, GA gun show and O’Conner had a factory display set up to push their unformed cases with steel screw-on bases. There were two versions: a belted magnum case and an unbelted rifle case. Nothing was formed; just straight wall unprimed empty unformed cases packed five to a plastic box. A cutaway drawing of a case is shown in Chris Punnett’s .30-06 book on page 274 with the O’Conner write-up. Chris’ mention of “a very few dummies without primers were made up at the factory” refers to my project. I talked the factory rep into making me a small lot (20) of factory .30-06 dummies after I convinced him that for the dummies to be correct, they had to be made and sold by the factory, not by me.

Your cartridge looks like the case mouth is significantly flared, so I think what you have is a normal O’Conner unformed case that someone has just stuck a bullet into, and a poor job at that.

BTW, when I gently explained to the factory rep that screw-on steel bases on brass cases were nothing new, and that O’Connor was going to have an interesting time trying to patent the idea, he looked at me like I was Satan. Only when I returned home and sent him some data and pictures did he believe me.


That case certainly appears to be one of the O’Connor Steelheads.

I have to admit that I have not heard of the 11mm/06. A 458" bullet in an '06 sized case would not work, IMHO. The case head is a nominal .467" which would permit a bullet of no more than .450" diameter, and even that diameter is being very optomistic.

Are you sure this isn’t a joke cartridge?? Mel is right.

You have a very versatile cartridge there. You can leave it as is and catalog it with your other “joke” cartridges. Or you can pull the bullet and, voila, you have one of the O’Connor Steelhead basic cases which has collector’s value of its own.

Just curious. Who told you it was an 11mm/06 O’Connor??


Thanks for the info Gents.

The head is unprimed (boxer). I bought it at an ammo show here in the UK from the same guy I got a couple of the .500 Phantom wildcats. It was marked up as an 11mm’06 O’Connor. I thought at the time that the bullet was wrong as it had belled the case mouth out. As the 2 Phantom rds are correct I assumed there was a good chance that the O’Conner was legit, It could be a joke but why bother to going to all the trouble to make the threaded case and head ?

I’ve looked at Chris Punnetts book and the case would appear to be as he described.

The steelhead basic cases never caught on with shooters and they are a collectors item today. O’Connor was also a rifle maker and moved around a lot. Where he is today I have no idea and he may be retired by now.

There is nothing inherently wrong with the idea of the steelhead cases. Shooters have experimented with them in high intensity cartridges for years. Following WW II when surplus steel '06 cases became available there were a slew of cases using the steel head with a brass front, all made like O’Connor’s.

The danger with them is that there are always a few shooters who will use them to try and push otherwise safe and sane handloads to new heights. O’Connor said he tested his cases to 140,000 psi. That exceeds the strength of most rifles by a good margin. He never recommended that they be loaded to such levels but the figure of 100,000 psi is common when talking about his cases. From a shooters perspective I cannot imagine why anyone would want to put his eyes behind a rifle/cartridge combination generating 100,000 psi but I’m just a girly-man when it comes to anything that might damage my pretty-boy face.

I liken a steelhead to my automobile. The speedomoter goes up to 160 mph but I have never driven anywhere near the red line. But there are drivers who will. They are probably the same guys who will load a 30-06 to 100,00 psi.


Ray/Mel, The possibility is then that I have a case made in the manner of an O’Connor or a very slight possibility that it is a genuine O’Connor.

I’d guess that with my luck it’s one made in the manner of ;) either way no problem.


I think the case is a real O’Connor basic. The length is correct as is the size of the steel base. The base should be stainless steel. Someone simply stuck a bullet in it, as Mel suggested.

l to r

O’Connor Steelhead magnum basic

O’Connor steelhead '06 basic

ca 1950s made from GI steel case head

ca 1950s steel base & case


Ray/Mel thanks for the info and pic’s. I think I can live with “original O’Conner case + Joke bullet” :)

If you would like accurate information regarding these cases I’m here and I hold the patent.
Don O’Connor

P.S. I never received anything from anyone at a Savannah gun show.