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Old March 28, 2020, 06:32 PM   #10
Senior Member
Join Date: October 21, 1998
Location: Colorado, USA
Posts: 2,875
What you think will happen does not always actually happen with blowback 9mms.

Slow powders and heavy bullets lose a lot through the ejection. At the same time, they are hard on the triggers and hammers (and brass if that matters). We have seen some 147 to 160 grain loads chrono slower from 16" carbines than from 5" pistol barrels. They also run a lot dirtier. Almost all of the catastrophic failures I have seen involved 147 or heavier bullets with slow powders in standard configurations. Sure, you can use .308 springs and heavier buffers and get most of the way there. In a test, with the SAME 147 +P factory ammo, we added 160 fps by going with a heavy buffer and .308 spring.

Lighter bullets and faster powders are the ticket for significantly increased performance in blowback 9mm PCCs and being safe. I start at 124s and go lighter from there. I have pushed 80/90 grainers past 2000 fps, but I too like the 115s the best. They maintain the accuracy out past 100 yards and just tend to be the best overall match for the blowback 9s.
Good Shooting, MarkCO
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