Saw an ad for a Colt Coltsman in 300 H&H which is built on an FN action. Considering buying it because it's a good price(cheap). Did FN lengthen their actions in the front or rear to make room for the longer cartridge? Lets say I wanted to replace the bottom metal in the future, are most custom mauser 300 h&h length floorplates set-up for the action being lengthened to the front or the rear? Just wondering if I would run into any issues by doing so. Thanks!

I've only had one in 375H&H. It was opened on both ends. That said the rear was simply thinned. The rear metal of the box was not moved to the rear simply thinned down. The remainder was in the front.

In my OPINION the vast majority of 98 style actions that were opened to handle something like the 300 & 375H&H were done that way. Simple and cheap.

I know some custom smiths alter the box in the rear more than thinning. That also requires more work to the ejector and bolt release.

As to custom bottoms simplest way is to ask the manufacturer.

I´m quite sure that this action is very similar which SAKO used to have in their High Power -models. I have one such action in my corridor and just some days ago measured it`s opened lenght for magazine. In my case it´s 90+ mm (3,54") and it seems that there is room in frontal area to open 2-3 millimeters.

All good info, thanks!