Your correct RR, the 90gr BT's are 6.5mm (.264) The closest Nosler BT is 100 grain and I don't think that old rifle will stabilize it. Not sure, as RR said, if that little 85gr BT would be good for a adult sized whitetail. Maybe with a neck shot or a perfectly placed "quartering away behind the shoulder tuck it in the sweet spot shot". But if you catch any real bone you will more than likely have a wounded deer to chase down. Barnes has a TSX in 80 grains for it. May try that one out.