I have used the NBT quit a bit taking deer and in all my experience I have never had one to blow up even at the short ranges here in the mtns.In fact I have taken a lot of deer with several different bullets and never had one to blow up even with making head shots.I haven't used the so called premium bullets because they are so expensive and I don't think the deer will ever know the difference.
When the SST came out I tried them and liked them,they are not that expensive,and found they worked really well.I don't have a 308 but do have a 30/06 and shoot the sst in 165 & 150 gr in it.If you reload you may want to try one of them,if the BT is blowing up.

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