It is a standard throat. I honestly don't know if the 3-groove is giving me more velocity; I actually think the opposite since the lands are twice as wide in a 3 groove barrel as compared to a 6 groove -- that there would be more land area to resist heat erosion per Dan Lilja but he didn't cover any velocity gain or loss (FAQ - Lilja).Do you think the three groove is giving you less drag and therefore more velocity? Did you have it throated long for these? I didn't even talk about that when I dropped it off to te GS (rookie mistake).
Mine is a 26" Hart magnum taper. I figure I subtract 30 fps from what your getting and I am still a bit off. My primers are showing a little flat, but bolt lift is easy. I get smileys when I chamber virgin brass witout firing so I think I am safe pressure wise. Any higher and primers are way flat. Still easy bolt lift but not gonna push it. This load is accurate and Matrix says it will function at 1500 fps so this is good for me. May play with H1000 once I get back home.
Check out #19 of http://www.longrangehunting.com/forums/f19/270-win-165-175-matrix-range-report-118585/index3.htmlA-62
As you can see so far velocity differences. Many others will come I am sure. I never got close to some of these but run the numbers even on my slower 2675 and this IS the bullet for the 270 at least for now.
For the 165s, you're golden!gun)Thanks all for the suggestions.
I have a Bartlein 1:9", 5R, Heavy Palma contour, 28" (26"finished).