The new numbers show "a world-class graphite project with strong technical and financial viability", according to CEO David Taylor.
The five million tonne per annum, 15-year project has been reconfigured, with an optimised plant that is designed to produce higher-grade products and protect flake size.
The updated BFS outlines a US$1.2 billion net present value and an internal rate of return of 51%.
Payback of the $324 million capital cost is estimated at 19 months.
The total does not include a $40 million contingency and $34 million in pre-production mining costs.
Not surprisingly, capex has risen since 2016, however operating costs have remained relatively stable at $639/t, compared to an average product basket price of $1847/t.
The original BFS outlined capex of $270 million, opex of $559/t, NPV of $1.7 billion, an IRR of 98%, and basket price of $2350/t.
Magnis is looking at ways to optimise the project and cut capex as it prepares for a final investment decision by mid-2023.
Steady stage production targets 236,000tpa at 98.5-99% total graphitic carbon from year two.
It already has some offtake agreements in place and is in advanced talks for more.
It has also started talking with third parties about funding.
Nachu is the only graphite project to be awarded a special economic zone licence in Tanzania to produce advanced graphite products. That exempts it from corporate tax and royalties for a decade.
The project, which is 220km from the port of Mtwara, has reserves of 76M at 5.2% and resources of 174Mt at 5.4%.
Magnis has been involved in Nachu since 2013.
Tanzania's government will have a 16% free-carried stake in the development.
Magnis shares, which have traded at A27-75c over the past year were last sold at 39c, valuing it at $378 million.