I think sniffing the silencers for solvent won't work

Needle in a hay stack? But again, the silence the police tested could of had vermin blood in it?
the super glue residue tests, I've heard the solvents break down DNA giving false data?
I've heard to if AP rifle had a barrel change its possible for an RFD to have sent the barrel of to be destroyed or may have it in the back of their shop? every RFD keeps back a record of barrel work done on a firearm?
as long you got the gun make and serial number, you could track the RFD that done such work!
since the RFD will only hand the old barrel back if you got a slot for it on your FAC? as its a compoment part like a silencer....?
But the chances are very slim!