Bea175: I have not shot any of the Sierra 39 grainers in my various 204's as yet but I have a lot of experience with the 35 grain Bergers.
In fact if I had unlimited funds and lived anywhere near a reliable source of Berger bullets I would shoot the Berger 35 grainers, exclusively.
All 6 (six) of my 204 Ruger Varminters shoot the 35 grain Bergers the best of any bullet I have tried in them to date.
And the Berger 35 grain bullets performance on all manner and size of Varmints is wonderful as well.
I had to "settle" on the excellent Sierra 32 grain Blitz Kings as my go to bullet in all of my 204's as they are cheaper and more readily available to me AND very nearly as accurate.
I use H 4895, Federal 205 M (match), and 4 different kinds of brass in my Rifles - it seems to me that my 204's are simply quite accurate no matter what I feed them and that includes factory ammo!
Now this - I am NOT playing "one up's manship" on you with this - my last trip to the range with any of my 204's (Remington XR-100 with Weaver V-16 variable scope) produced for me a group (5 shots at 100 yards) measuring .255". This was in late July of this year.
I noticed that your group was .256" in your photograph - coincidence, I think, that similarity in group sizes.
I highly recommend you trying the Berger 35 grainers in your already accurate 204.
Hold into the wind
VarmintGuy