A wildcat does entail a bit more work at the beginning than a factory chambering. Also, some wildcats require a lot more work than others.
I designed this one a few years back, together with 3 others based on the 404 case.
The others are a 375, 338 and 270.
I have been using the 375 for all my hunting in Africa, and it has served me very well.
The reason I am building this on now is for hunting plains game - I have plenty of other rifles I can use, but I just felt I wanted to build a new one on the new Sako 75 action.
I had a custom set of dies made by Neil Jones. The sizing die is a bushing type, and has several bushings to neck the parent case down to different calibers.
The different steps are described in this post.
http://www.serveroptions.com/ubb/Forum6/HTML/004474.html
There is no special reason to build this wildcat really, as the 300 Remington Ultra Mag is very similar.
Of course, once the cases have been formed, they can be used many times.
If you decide to build one, and need any information, just ask, I will be happy to help you.
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saeed@ emirates.net.ae
www.accuratereloading.com