Twist rate!

[alberta boy]

1:12 struggle with long, high BC bullets. Like 178gr Eld-X. And gives marginal success with 168gr Barnes -ttsx.

The OP stated he was using 140 to 170 gr bullets , while not optimal , a one in 12 twist would stabilise these bullet weights . That's why I suggested a 1 in 10 twist as a better option .
AB

 

[MTheaded but happy]

Faster twist can stabilise heavier bullets, but can also over stabilise lighter bullets.


Regards

I believe that Litz debunked the belief that it's possible to "over stabilise" bullets around 10 years ago and that there are benefits to spinning bullets hard , particularly if they travel through the transonic range . Providing the bullets aren't spun to destruction of course .