Deadpool
03-16-2015, 12:04 PM
I've been experimenting with different powders to "make the most" of this 18" barrel in a direct-blowback 40S&W. Longshot and Herco have been pushing a 174-175 grain projectile beyond 1350fps.. With a shorter OAL I'll get higher pressures and higher velocity. Max out my OAL to fit the most powder in, I'll probably get it up to 1500fps but I have pressure to watch out for. When those pressures begin to exceed (pressure signs on every case) tolerances, I may switch to an even slower powder, such as AA#7. I began considering lightest projectiles and heaviest projectiles... Lightest for greater than 1500fps, and heavier for a max power subsonic. Light boolits seem to be 140gr, or maybe find a deep HP pin to get me 115gr without it busting apart mid flight. Or I might try PC zinc for these ultra-light rounds. For now I'm looking at moderate to heavy.. And what I'm considering could be construed as very heavy.
I found a nice looking mould that gives a 9mm profile boolit for .404 at 240gr. It's gas checked and has a couple of driving bands, and they have the option of modifying the mould to make it shorter. So I was considering ordering this with a single large driving band (for PC) and no gas check, and remove all of the length that the gas check consumed to the base driving band, or half of that length. Maximizing cavity volume probably increases mass to 250gr and losing most of the base should reduce it to 225gr or so. The most powder after seating this long boolit would likely be in the range of 3.5 - 5.0gr of Longshot, where 7.7gr was my max with a 180gr boolit.
Would I move back to a faster powder like Unique or Titegroup to get this heavy round moving fast enough (750 - 1050fps) or do you think Longshot/Herco would be right in the ballpark of using the whole barrel to target this velocity range without going overpressure?
I found a nice looking mould that gives a 9mm profile boolit for .404 at 240gr. It's gas checked and has a couple of driving bands, and they have the option of modifying the mould to make it shorter. So I was considering ordering this with a single large driving band (for PC) and no gas check, and remove all of the length that the gas check consumed to the base driving band, or half of that length. Maximizing cavity volume probably increases mass to 250gr and losing most of the base should reduce it to 225gr or so. The most powder after seating this long boolit would likely be in the range of 3.5 - 5.0gr of Longshot, where 7.7gr was my max with a 180gr boolit.
Would I move back to a faster powder like Unique or Titegroup to get this heavy round moving fast enough (750 - 1050fps) or do you think Longshot/Herco would be right in the ballpark of using the whole barrel to target this velocity range without going overpressure?