I work with Huglu shotguns frequently, I'm told they have a silver hardchrome finish on the receiver and black hardchrome on the barrel.Would like to remove this finish on the exterior for blueing but do not want to disturb the engraving by buffing.Also would like to keep the hardchrome on interior surfaces as it's good for corrosion resistance.Could case coloring be done without hardchrome removal?
Any advise would be greatly appreciated.

I think the hardchrome rumor on huglu guns is most likely BS.You cant engrave hardchrome, nor can you retain detail by engraving and then chroming. I think that they have a chrome rich finish that they are calling "hard chrome," but it should not be confused with the common process of HARDCHROMEing which is and entirely different and more expensive process.

I may be wrong but thats my belief.

Also, you can NOT color case harden hardchrome(if that is in fact what it is), and you are likely to ruin the gun if you try. You will most likely end up with peeling/flaking chrome if you attemp this.

Also, you should be able to remove the chrome chemically so that you can refinish anyway you see fit fairly easily

http://www.hugluarms.com/new_page_4.htm

The only hardchrome I see mentioned is the bore.