Why did changing buffers change my POI?

[65Grendelier]

Lol I clean my chamber.

I precision reload.

6.5 Grendel:

123 eld-m MV 2425 SD 9
31.2 cfe 223
Bto 1.658”
Cci 450
Starline brass base to shoulder 1.212” fired cases 1.2165-1.217 (.005” bump)
Trim length 1.510”

Charge master link powder measure

Lots of precision shooters don’t clean their barrels until they stop grouping.

I’m not an amateur, well at least not a noob… just trying to understand what I altered, was it barrel harmonics?