Your criteria of smooth bolt, gas handling ability and strength have commerecial FN 98 written all over them. You can find them for $400, but you may have to break down an existing rifle to get one. I�d drop the 93�s, 96�s and Santa Barbaras.
Under most circumstances, I wouldn�t bother with a military 98, since you�ll spend 2-3x the cost of a commercial action to make it anywhere as nice. The exception is when you�re building a new rifle in the chambering for which that action was originally chambered. Mauser magazine boxes and feed lips are set up for a specific cartridge, and may not feed smoothly with something else. Getting them adjusted properly can be extremely expensive, so if you decide to build a 7x57, it might be worth starting with a military 98 that was built in 7x57. This also makes a good case for building a custom 30/06 on a commercial that was originally a 30/06.
The H&H cartridges can be a problem in a standard 98, since the magazine box has to be lengthened for them to fit. That also means shortening the feed ramp, which some people feel reduces the action�s strength. It�s probably best to go with a true magnumn-length action for them. That said, various factories have built 375�s on standard 98 actions over the years, so this is probably more of an issue in a conversion done by someone who may not have known what he was doing.
A Kuhnhausen Mauser Shop Manual will have enough details to keep your head spinning for months as you plan this project. Brownell�s probably has them.
Okie John
