Will it fire on semi auto lower,

I should.  IIRC, the only difference is the weight.  Actually, I think Oly has different weight FA bolts available for different rates of fire.  Put any of them in a semi-auto gun, and all you get is a gun that cycles one round with one pull of the trigger a little faster or a little slower (measured in milliseconds).

I assume you mean the full auto bolt carrier - the bolt would be identical.  It will fire as Corvus said, but he forgot to mention that it would be illegal to use in a semi-auto.


Stupid, but I didn't make the rules...

It would not be illegal to use in a semi auto lower. Just like the Colt 9mm bolt which are most all full auto carriers, even when shipped from the factory in the semi auto guns. Since the 9mm's use a spring loaded firing pin rather than a floating pin like in the .223 carrier they can not fire full auto with hammer follow only so will not facilitate a full auto conversion buy just the use of that one part like in a .223 gun.

Quoted: It would not be illegal to use in a semi auto lower. Just like the Colt 9mm bolt which are most all full auto carriers, even when shipped from the factory in the semi auto guns. Since the 9mm's use a spring loaded firing pin rather than a floating pin like in the .223 carrier they can not fire full auto with hammer follow only so will not facilitate a full auto conversion buy just the use of that one part like in a .223 gun.

Actually it is illegal in many states. The reason a full auto bolt/carrier is legal in a Colt 9mm is because they never made two different models. They only made one carrier for their 9mm... but in .223 they made two: A semi, and a full auto.

The BATF calls this "Constructive Intent" and it is a crime. The only reason you would have a machine gun part in your semi AR is because you "intended to construct" an unregistered machine gun. I didn't write the rules but that is how they interpret it.

If it came from the factory with a full auto bolt and was intended to be sold as a semi-auto gun then it is most likely legal and the factory got approval like Colt 9mm's... otherwise you may get yourself into trouble.

The reason a full auto bolt/carrier is legal in a Colt 9mm is because they never made two different models. They only made one carrier for their 9mm...

With all due respect, I do not think this is correct. I recall an old MGN article with pictures of Colt 9mm semi and auto bolts. I remember the comment that John Norrell would mill out a Colt 9mm semi bolt to auto specs.

What I had always heard about it matches closely to what Tommy Brown said. But I've been wrong a couple times before. ;0)