Originally Posted by
Larry Gibson
“So is pressure the limiting factor and RPM merely a yardstick? Gear”
I’ll have to say that Starmetal, 45 2.1, probably BaBore, myself and a few others have disproved that one. Gear is also correct in his previous statements questioning that pressure is the limiting factor. My .308W load with a 311466 that runs 2600+ fps with excellent accuracy to 300 yards (farthest tested) also runs at a measured (Oehler M43) 40,000+ psi not guessed at by consulting manuals, using QuickLoad or any other "guestimation" method. If pressure was the “limiting factor” then, according to Lee’s chart that 16 – 18 BHN bullet should have reached its “limit” between 20,000 and 23,000 psi and accuracy should have gone south there. Yet I push them at 2600+ fps/40,000+ psi with 1 ˝ moa. So how is that if pressure is the limiting factor?
Let’s consider what else I’m doing; loading procedures are standard for cast bullet accuracy (fire formed NS'd cases and bullet sizing to fit the throat) with no secret ingredients of buffers or special cases, the 311466s are cast in a 4 cavity mould with visual inspection only and are not weight sorted, a slow burning powder at 100+ loading density, plain old Javelina lube and Hornady GCs, and use of a regular primer (brand doesn’t seem to make any difference)………so what could be the reason for such accuracy at 2600+ fps at 40,000+ psi? Might it just be because I’m using a 14” twist barrel and controlling the RPM by keeping them at a low rate. At 2600+ fps the RPM is 133,700+ with the 14” twist. In a 10” twist the RPM at 2600+ fps would be 187,200+, probably over the RPM threshold for that alloyed bullet.
Funny how that works isn’t it.
Larry Gibson