Re: 165gr Sierra Gamekings in a 308
Hi Rick, I find the 165gr GK to be a very slow killer out past a couple of hundred yards. It might be ok if you are in open country but is a no go if your animal can escape into cover. Wounding is good but not as vivid as you would get using either the 155gr Amax or Berger VLD bullets at extended ranges. The heavy GK's (including the HP), bore a deep but narrow wound which is about .75" wide through the lungs. The above target bullets give a widely diffused, much faster bleeding wound. Nothing else comes remotely close at lower velocities.
If you need controlled expansion, the 165 grain Hornady Interlock is pretty good/ softer than the GK at this weight. Also, weird as it may seem, the 150gr SST is pretty good out to about 500 yards.
Varget is too slow for the 20" barreled Tactical. If you are using a max listed manual load, velocity will be about 2500fps. You really need to switch to (from fast to slowest) BLC2 or H4895. Approximately 45gr of H4895 will give you 2650fps. Just bear in mind that to achieve good velocities in the tactical, you will have to run higher pressures than in a 24+" tube. I am using either Hornady Frontier of Win brass and case life is fine. I am finding through our accurizing services (and my own M700 Tactical) that 46.5gr of H4895 drives 150 grain bullets at 2860fps and 155gr bullets at 2820fps. I tried lowering the charge for the 155gr bullets by .5gr but accuracy fell off. My particular rifle has three sweet spots when running 150-155gr bullets. The first is at 2500fps followed by 2650fps, and finally 2820-2860fps. Average group size is .4" but if I load to say 2700fps, groups open right up to between .75 and 1".
Hope that helps.