Heavy for caliber bullets

[NorAlta243]

Hi Bryan,
With the benefits of heavier, high BC bullets being realized in 7mm and 30 caliber, I was wondering if there were plans for heavier 6mm and 6.5mm bullets in the works. I know there must be a tipping point, but seems like there would still be some room here. Has this been explored? What are the limiting factors?
Thanks

 

[Bryan Litz Ballistics]

They exist. The trend line for 'heavy for caliber' bullets goes:

.224: 90 grain
.243: 115 grain
.264: 140 grain
.284: 180 grain
.308: 230 grain
.338: 300 grain

This trend line represents bullets that are scaled proportionally. In other words, if you scale a 7mm 180 grain bullet down to 6.5mm, it would weight 140 grains.

This trend line is the upper limit of bullet length/weight for caliber which is known to be reliable in many rifles and cartridges. There are bullets that exceed this trend line; for example the .264 cal 160 grain. Of course this can work if special care is taken regarding throat length, copper fouling, powder selection, etc. but they're certainly beyond the norm.

Take care,
-Bryan