Re: Help me decide caliber for new build
For brass on the 7mm/300, I'm planning on using 300 WM brass and simply necking it down - not a complex operation. There is plenty of 300 WM brass on the market and likely less expensive than Dakota (Norma?) brass. I think for the foreseeable future, 300WM is going to be around so brass will also be readily available. I don't know about the Dakota...
Admittedly, sizing dies are another matter. However, any of the larger manufacturers (Hornady, et al) would make one without a problem and probably not too expensively. Otherwise, collet seating dies are the way to go and they're caliber specific so no problems there.
Neck sizing, once the cases are properly full-length sized requires nothing custom or special, so the 7mm/300 in this regard is standard.
Also, for a reamer, it would be worth a call around to some of the more notable 'smiths. Certainly one of them has a 7mm/300 reamer...