The Howa 1500 rifle action is one of the best bargains on the market.
It is a one piece CNC machined action from the company in Japan. This is not a US made action, and I always throw that out there so the buyer knows the origins.
We have built a ton of rifles on the Howa 1500. It's a very strong action, it has much more rigid strength than a Remy 700 or a Browning, and the flat bottom makes it a bedding dream. The bolt is all one piece, not assembled or brazed/tacked in place and the extractor is a very solid AR style extractor, so you have no worries there.
This action only have 2 locking lugs, but two are plenty and most hunting, shooting rifles only have two. Generally, from the factory, the lugs make good contact with the bolt face and don't need to be hand lapped for consistant lock up.
Weatherby is importing almost the exact same action and assembling it as their Weatherby Vanguard line, which you will notice they are selling with an accuracy guarantee. A large portion of that has to do with how solid the action is.
I built a .25-06 on a Howa Long Action for my grandfather before he passed and he said it was the nicest shooting long gun he had ever shot. But I think he was probably biased.
I think you have made and excellent choice in going with the Howa. Bell & Carlson is a very good stock company and they make a great stock that is a drop in for the Howa 1500 and a good bedding job. If you combine those components, and you do your part, I think you will have an moa shooting rifle out to 400 or 500 fairly easily.