Hi I plan to buy an Olympic 9mm upper soon is it possible to put the bolt etc in the 7 1/2 upper? If so what would I have to put in the 71/2 upper?

Thanks

You'd have to get an oly 9mm 7 1/2" barrel with an oly 9mm barrel extension, and an oly 9mm upper with the oly 9mm ejector.

Then put in the Oly 9mm bolt/carrier and you're done... you could use anyone's ejection port cover, forward assist parts, charging handle and rear sight parts you like.

Anyone's upper can be drilled for the 9mm oly ejector if you prefer to do that yourself, and reuse an existing upper, so the only parts you can't really make yourself from other parts are the bolt/carrier, barrel and barrel extension.