Originally Posted By: spotstalkshootI found the 39 Sierra to be very accurate with imr 8208, however it was inconsistent penetration wise on coyote. After shooting a few, I went back to my 17 rem with 29 gr WCD bullets. Next winter I will run some 35 gr Bergers through a few coyote for comparison. My rifle has a 1/10 twist barrel. The faster twist maybe a factor especially on the frontal shots inside 200 yards.
My experience with the 39SBKs was similar to yours but I was shooting a factory 12 twist.. I’ve since ordered a 1:11 MullerWorks to replace the factory tube. Once that’s installed I’ll be trying the 40 grain Berger’s.
To the OP, I’ve read from many 204 owners that 1:12 is marginal at best for the 40s. I’ve never tried them personally. I can attest to the 39 SBK being very accurate out of both of my CZs in 204.