Anyone that has ever played with Quickload for 30 minutes can explain why increasing the OAL increases usable case capacity and lowers pressures. Those that wish to get as much velocity as possible can add a little powder to bring pressure back up to the maximum suggested.
There are several members on 68forums that own or use pressure test equipt. and have tested the above. Since 2006 many of the members there have been involved in correcting all of the mistakes on the original 6.8 design. Many have been involved in increasing the performance by tweaking designs and perfecting loading combinations and procedures.
There are probably more wildcat guys developing cats on that forum than any other forum, so many that they have now started a wildcat forum.
If there is anyone still following this other than the 2 this article explains more of the peak pressure problem solution.
The effects of engraving force and bore area on pressure-
http://www.dtic.mil/dtic/tr/fulltext/u2/a431357.pdf
CONCLUSIONS
1. The baseline heptagonal barrel will exhibit peak chamber pressures about 15 to 20%
higher than the same cartridge loaded in a standard M240 barrel. This is due primarily to
the increased resistance pressure early in the in bore travel of the projectile.
2. The increase in peak chamber pressure could be reduced by either increasing the free run
of the projectile prior to the start of engraving or by reducing the forcing cone angle in the
barrel.
3. A slight decrease in resistance force was observed for the 2.5 deg half angle forcing cone
compared to the 1.2 deg half angle forcing cone found on the M240 barrel baseline. It is
believed this difference is due to a reduction in the plastic deformation of the M80
projectile in the 1.2 deg barrel.
4. The addition of lubrication to the M80 projectile exterior increased the engraving force in
the baseline M240 barrel with 1.2 deg half angle forcing cone, while it decreases the
engraving forces in the 2.5 deg half angle forcing cone barrel. Likewise the push force
standard deviation increased with lubrication in the 1.2 deg half angle forcing cone, and
decreased in the 2.5 deg half angle forcing cone.
5. Projectile construction and elastic modulus appear to play significant roles in the
resistance pressure of small caliber projectiles.
http://68forums.com/forums/showthread.php?56136-Reloading-and-pressure-something-to-ponder

Last edited by constructor; 05/02/16.
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