Sierra Heavy TMK 6MM Testing

Can’t speak to any of the loaded ammo, but the cases can take higher pressure & they said that due to the construction, they have additional powder capacity. That would mean an additional 2 grains of powder in 223/556. They can’t be reloaded. I havnt received the 250 cases I ordered yet, but will update when I do. I’m already getting 2800 fps from my 16” bbl (1/7, .100 fb) with 80’s and N150 in ADI brass.
N150 is one of the overlooked powders for this use case. As well as N540. Everyone wants to use 8208XBR. Sure it works, but velocities are very low with heavies when using it
 
So you prefer N150 over N540?

There's some tradeoff. Single vs double base powders, 540 will gain some speed, but probably be a little less temp stable.

N150 is extremely consistent, if a touch slow. Very very popular with competition shooters in some of the 6's.
 
They released a video with a general outline of when to expect bullets to be available.

It seems to be accurate so far. I posted it back a few pages. It’s on sierras YouTube channel.

 
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