European brown bear (400-700) pounds. 12/70 slug or a 7,62 × 54 fmj as last solution?

the most common calibres for shooting European brown bear are 9.3x74 and 9.3x62. Most of Europe doesnt allow less than 300 win mag and shotgun slugs not allowed. Its not permitted to shoot one without a licence EVEN in self defence accross all of eatern europe

Obviously the same round used for hunting may not be acceptable for self defense. In hunting, you may want to shoot out to or beyond 300 yds (you guys that have not made it to the moon may have to convert it to meters if you don't know yards) and it is OK if it runs a couple of hundred yards. For self defense, you want to stop it IMMEDIATELY from a short range. I would go with slugs not a German killing round.

My preference would be the shotgun for the following reasons. 1- I'm not concerned about having a scope or other optic on it that may get damaged while hiking. 2- the slug will be adequate for the bear you describe and in most cases your talking about a close in shot for defense only. 3- if needed you can also take with you different loads for that shotgun, the reason is if you got lost then you can hunt rabbits or birds for food. That could be a challenge with the rifle on smaller game. 4- Depending on where your hiking, dirt, snow, humidity, ice, or rocks are going to be less of an impact on the shotgun than on a rifle action or optic.

Just my thoughts to your question.

Where will you be hiking? That may affect what, if any, firearms which you can carry. Find out about the local regulations.

The 12-bore will be considerably more effective. You'll of course want to check local regulations.

I have killed 7 Brown Bears with a Hi-Point .380 model Super Deluxe Bear Eliminator with camo grips. You

can't go wrong and of course use FMJ.

Edit: Serious answer DA.

("So whats more effective against a lets say 600 pound bear? ")....a 300 pound slug....no contest.

If you carry a rifle most likely you will have it slung over your shoulder. Not a lot of speed in swinging it around, lining up, taking the shot. Plus it is 6-10 pounds of weight. Get a Ruger Alaskan in 454 Casull and you got it all covered. You can draw and fire one handed.