Thread: 223 69gr TMK / 77gr TMK damage to projectiles while seating

@7mmsaum cant neck size on a semi-auto action (Ar15). I do need to check the chamber throat length but I suspect the throat is quite short, 2.265 is it anyway for the mag, though I am single loading on a platform now. I think my club has a hornady kit so I need to do that, hopefully next weekend. I am using HP match grade Sierra tmk bullets in a 1 in 9 and so far the 77gr seem the most accurate over the 69gr TMK but I have not tried 75s yet, Ive not seen them about. I posted speeds earlier but the best accuracy seems to be 2950 fps ish for the ADI 69gr factory, not chrono'd the xtac 77gr PMC smk factory load yet but they also shot very well around 3/4moa from a std 4140 stag barrel.