The idea that you would need scientific knowledge to put something inside a silencer is laughable. Planting or manufacturing evidence is criminal and criminals take risks.
Planting blood on the outside is one thing but opening it up and putting it in as far as the 8th baffle quite something else! If the scientists didn't even think to open it up on the first occasion (13th Aug) what on earth makes you think Mrs Eaton would have the wherewithal to do so in order to plant blood, diluted period blood at that, as far in as the 8th baffle! And if she did don't you think she would be saying something like 'Oooo it seems to extend into that little hole I think you had better open it up and have a look inside'!!!!!! But no it was another month before the scientists decided to open it up and look inside!
Mrs Eaton has no history of criminality.
If the silencer was not used then the blood is a result of deliberate contamination. They are both fundamentally linked.
If being the operative word!
I am asking you to challenge it. 
I have.
That brings up another point as to why there is no bone fragments in the silencer also. Nicholas caffel suffered three contact wounds to the head.
"Test shots on live pigs destined for slaughter showed that bone particles are a feature of backspatter from close-range shots to heads. Contamination of nearby surfaces by bone fragments and bone-plus-bullet fragments, as well as other organic debris, appears to be quite heavy."
"Detection of Bone and Bone-Plus-Bullet Particles in Backspatter from Close-Range Shots to Heads," Journal of Forensic Sciences, Vol. 36, No. 6, 1991, pp. 1745-1752,
It depends on many factors. Wound site and muzzle velocity being two. In this case the wound site was wrong for bone fragments and the muzzle velocity too low.