Has anyone attempted a build with a .410 upper on a pistol lower and is it NFA legal?

The bore is less than .50, so I think it would be ok.

you will still have to have a 18" barrel unless you can make it feed 45 LC.

Any way to make one out of this ?

Interesting question. With the resent classification of factory built pistol gripped shotguns not being shotguns it leaves it open for interpretation. It would be reasonable to say that if it is built from a virgin receiver it would fall into the same category as the PG shotgun. If so it barrel length would only be a consideration in the overall length, which would still need to be greater than 26" to remain a title 1 firearm. With a carbine length buffer tube that would be about an 11" barrel.





On the other hand, if you have a lower that has been used as a pistol, adding a smooth bore upper with a barrel under 18" would most likely result in a smooth bore, shotshell pistol which is by definition an AOW. If the barrel was over 18" it still must meet the greater Than 26" minimum length to remain out of the purview of the ATF.  





So, it may be legal to build it on a virgin lower provided it was greater than 26" long overall and it remained only in that configuration, i.e. no swapping uppers with a pistol upper.





But this is just my interpretation, if your considering building one I strongly recommend writing a letter the ATF for their determination.  





ETA: If the .410 barrel is rifled then a short barrel pistol configuration should be GTG.