A .30 caliber 220 gr RN is a good bullet, although I believe the heaviest bullet Speer makes currently is 200 gr, perhaps your's are Sierras. You should be able to drive a 220 at 2300 fps from the .308's 18" barrel. This velocity would result in a trajectory that, with a 150 yard zero, would be 4" low at 200 and a foot low between 250 and 270 yards. Try working up a load with Winchester 760 or H-380. Either of these powders will produce good results when used with a heavier than normal bullet in the .308. A starting load with W-760 bewhind a 220 gr RN would be about 38.0 grs
If your son wishes to take advantage of a flatter trajectory, the 165 or 180 gr TTSX at 2700 and 2500 respectively will reach out allowing for an additional 50 yards of range over the 220 gr RN. I would consider Winchester 748 as the propellant, particularly with the 165 gr bullet.
My personal opinion tells me that this child, yes child b/c he is not even a teenager jet shouldn't be pushed into unnessesary and risky endeavour of hunting grizzly bear no matter how "mature" he seems to be or what the law permits him to do. You as a father having his destiny in your hands should know better than that.
just to answer some of the questions and comments( and thanks for your thoughts in those regards) The grizzly are inland. We will be hunting around the Tumbler Ridge area. We are not permitted to hunt bears over bait in B.C. I also believe that him being more comfortable with the .308 is the better choice over getting him into a magnum caliber. I had toyed with the idea of putting a brake on the .300 win mag. Definately more gun how ever i still think it is better to work up the .308 loads as he is confortable with it. In the area we hunt, black bears are also everywhere and their season is open at the same time. I certainly wouldn't send him out hunting for a grizzly by himself. In B.C. a hunter is considered a youth and needs to be in direct supervision of an adult untill they are 19yrs old. I will be beside him every step of the way with my .300win mag as a backup gun. I wil also purchase a black bear tag as well. Not really looking for one but as i said there are lots in the area as well. He is a very mature boy and I am not pushing him into anything. Origionally i had not thought about letting him apply for the tag until he was a bit older. After i told him he drew the tag it would be easier to talk him out of a kidney than that tag. I am so pumped for him its going to be great. Thanks again for your responses.
As pretty well everyone else has said a .308 will be fine with good placement and bullets. If this were my son I would be ready to back him up the second he shoots with something big and would advise him to pour the lead on after the initial shot and you should do the same.
i too would be looking for a 180 partition. a little shorter than a 180 tsx so affords a little larger powder capacity.