frizzellr is right on the money. I would never use anything less than a 100gr bullet to hunt deer. Many of the lighter weight bullets are designed for varmints.
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If you can't shoot enough gun then go home!
95 grain nosler partition or 90 gr barnes x will perforate a deer too. Nobody wants to use them, but Ive seen some deer shot with 105 gr Speer roundnose too that worked good for a 6mm. You just need to put the shot in a soft spot and dont count on a whole lot of penetration from these little bullets. I know a guy who shot deer for several years with 70 gr sierra bthp' s, but thats not the best bullet to use. He never lost a deer though, so its all in where you hit em.
I have been using the 85 gr Barnes XBT for both deer and antelope and I have taken quite a few animals with them at over 200 yards and only had one bullet that didn' t pass completely through . So I guess you could say I don' t agree with the idea that the 100 gr bullet is the bottom line . I have tried quite a few different bullets and combinations over time and the Barnes bullets are by far the better one in my opinion.