Thanks - going back to a chrono with Nosler Custom Ammo is what I'll do next. I'm confident the reading is correct as I shot at 300 and 100 yds and ran the ballistics calc backwards to determine speed based on trajectory. The calc told me something less than 2800 which I didn't believe, so I shot it over a buddy's chrono and confirmed it was correct (4.25" high at 100, 1/2" low at 300).
I pulled a couple bullets and remeasured the powder as well. 68 gr on the dot.
If the Custom ammo comes out slow (3100 is factory spec) what should I suspect as the faulty variable?? Something in the rifle?
Just because the rifle is slow, does not necessarily mean there is anything actually wrong with it. Especially anything a gunsmith could address, short of a new barrel. You could well have a perfectly good chamber, but on the maximum end of spec, coupled with an excellent smooth barrel also on the maximum end of spec diameter.
In a perfect storm scenario, one could couple the previously mentioned factors with lighter than normal brass.
If the rifle shoots accurately, the rest is just a matter of load development.
Which primer are you using? I ALWAYS use magnum primers in the 264. A hotter primer could gain you a few fps.
While many 264 owners swear H870 was the Holy Grail of powders for the 264 with 140 gr bullets, it is too slow for my old Win 70 classic.
My rifle performed well with H1000. 65 gr of H1000 gave 3050 fps with the 140 gr NP. While it required 67 gr of H1000 to make 3000 fps with the Sierra 140 SPBT.
Magnum, while being very similar to Retumbo in burn rate, is a very dense powder and easy to get large weights into a case. It also feeds very reliably through a powder measure. My rifle took 69.5 gr of Magnum to make 3000 fps with the 140 Sierra SPBT. 72.5 gr of Magnum produced 3150 fps with the 140 Sierra in my rifle.
I think that either H1000 or Magnum will get you to 3000 fps with your bullet of choice. Magnum will probably get you to 3100 fps. With the consideration that H1000 is the lesser temperature sensitive of the two.
If you were working with bullets less resistant to engraving than is the 140 PT. I would also recommend trying some H4831 over the chronograph. H4831 might well be a good choice in your rifle with a 130 gr or 140 gr accubond.
