During the design stages of the 6.5mm true short action wildcat the 6.5 Romulus I did some case capacity modeling/comparisons on Quick Design for a handful of the large capacity 6.5mm cartridges....... some of these were not on QD and dimensions were taken from the Ammo Guide website and plugged in to generate QD case capacities while others are simply the parent case necked down with no other changes ...... several are my wildcat designs , 6.5X68s MI (max imp.), 6.5 Long Range Hunter, 6.5 Prometheus & the short action wildcat 6.5 Romulus ....... While the max case length on the 6.5 Romulus can be run at WSM length for 102.5 gr capacity, function in a 2.830" coal requires deep seating of bullets to ogive that reduces case capacity anyway, the design intent was to operate in short actions factory mag boxes without requiring alterations....... there is a design on the full WSM 2.100" case length for max case capacity with mag box alterations, both are in build stages at this point.......
Some of you may have differing case capacities derived from different sources or actual cartridges and I am not contesting those results just presenting what the Quick Design program shows and to provide a quick reference table for those that are interested in the case capacity differences, I also provided the case h2o capacity with the necks cut off ...ie... up to neck/shoulder junction as a usable case capacity cross reference for all the cartridges.......
CARTRIDGE............................H2O to top of case mouth............H2O to neck/shoulder junction
6.5-338 Lapua.........................112.4 gr.....................................109.3 gr
6.5-300 RUM...........................109.2.......................................105.8
6.5 Long Range Hunter..............108.6.......................................104.6
6.5-338 RUM...........................105.7.......................................102.0
6.5 Prometheus.......................105.0.......................................100.5
6.5 STW..................................99.6.........................................96.1
6.5-375 Ruger...........................99.5........................................96.7
26 Nosler.................................98.4........................................94.9
6.5-300 WBY.............................98.4........................................93.4
6.5X68S MI..............................98.1........................................94.4
6.5 SIN MATCH.........................97.3........................................93.6
6.5 Romulus (longer case).........102.5........................................99.0
6.5 Romulus.............................96.0........................................92.5
Some of you may have differing case capacities derived from different sources or actual cartridges and I am not contesting those results just presenting what the Quick Design program shows and to provide a quick reference table for those that are interested in the case capacity differences, I also provided the case h2o capacity with the necks cut off ...ie... up to neck/shoulder junction as a usable case capacity cross reference for all the cartridges.......
CARTRIDGE............................H2O to top of case mouth............H2O to neck/shoulder junction
6.5-338 Lapua.........................112.4 gr.....................................109.3 gr
6.5-300 RUM...........................109.2.......................................105.8
6.5 Long Range Hunter..............108.6.......................................104.6
6.5-338 RUM...........................105.7.......................................102.0
6.5 Prometheus.......................105.0.......................................100.5
6.5 STW..................................99.6.........................................96.1
6.5-375 Ruger...........................99.5........................................96.7
26 Nosler.................................98.4........................................94.9
6.5-300 WBY.............................98.4........................................93.4
6.5X68S MI..............................98.1........................................94.4
6.5 SIN MATCH.........................97.3........................................93.6
6.5 Romulus (longer case).........102.5........................................99.0
6.5 Romulus.............................96.0........................................92.5
