The possibility that hidden away and concealed in the voids of the rifling of the gun there exists victims blood and DNA is very high!
On occasions I had cause to discuss the Mallinson theory together with Glen Smith and Keith Mallinsons in 2003 / 2004, it became somewhat obvious to me at that time, on those occasions, that it could be a pivotal moment in the case...
What Mallinson proposed was that the voids of the rifling inside the lining of the barrel could be cleaned out using a special tool suitable for such a purpose, and the debris collected or gathered upon / in specially prepared paper free of potential contamination! The results of the cleansing process could then be checked for any blood group activity and DNA using the very latest techniques! Nobody has done this during the 32 years since the tragedy! I believe the reason the defence haven't yet got around to doing it, is due to cost! On the other hand, the prosecution haven't done it because they know the results have the potential to collapse the case and set Jeremy Bamber free!