Re: What causes hang-fires?
On bolt misalignment, first you should disassemble the bolt and pay mind to the causes of it.
You'll notice that the striker can & will release with the bolt turned plus xdegrees to minus ydegrees, and that in each case energy is lost. Often the piece that rides up the cocking ramp, strikes the cocking ramp on release if the bolt isn't turned far enough, driving the bolt handle downward(along with your muzzle velocity). If the bolt is overturned there is friction against a cocking piece side, and on the striker's near-full travel the bolt handle twitches upward(and again MV drops).
The sear section of the cocking piece also drags within it's action slot under the shroud.
Some bolt actions are better than others in this regard, but my guess is that they ALL do it(including aftermarket actions).
It's one of many flaws in todays standard design.
Cycle & dry fire your action repeatedly while watching the bolt and shroud. You'll see alot of ugly movements going on each time differently...
The only fix is to remove all the slack at the rear bolt, and make the bolt turn index to perfect alignment everytime using alignment pins(if needed), a stop, or ball detents.
These same actions can center the rear of the bolt and lightly preload lugs.
But anyway, I think the powder load/temps were the biggest contributor to your hangfires.