Namib
Is your comment regarding heavy bullets not working well in short barrels based on a velocity requirement or that most 6.5 barrels run an 8 twist, rather than something faster like a 7 or 7.5 twist, whether short or not? Is comment tied to a stability calculation generated by velocity or twist rate, or both?
I should have been more specific: Heavy bullets often have high BC and for target shooting purposes, choosing a very heavy high BC bullet will always help wind drift (if your barrel has a fast enough twist rate to stabilize it), whatever your barrel length, even at shorter distances. Wind is always the biggest factor, just check out one of Cal Zant’s WEZ analysis. This benefit comes at the (very minor) cost of more bullet drop, so you have to dial a little more, but no big deal as long as your scope has enough elevation travel. Even a 200 fps lower speed will have very little effect on the stability factor and it is mostly a question of required barrel twist rate. At a worst case 200 fps slower muzzle velocity, group size will go up only about 10% due to wind drift differences caused by the slightly longer hang time of the bullet. BC benefits quickly overwhelm the disadvantages of lower muzzle velocity. The increased wind drift of the bullet caused by a short barrel is really not that much, and unless you are in the top 5 of your sport, it is not going to matter.
Of course if you want enough speed out of a short handy rifle with an 18” barrel, just go up to a short magnum caliber (eg from 6.5 Creedmoor to 6.5 PRC). And live with the muzzle flash, blast wave and extra noise, and the increase in recoil (which is quite benign for all 6.5 calibers).
BTW: If you are in the PRS or NRL games, you will probably pick a 6 mm caliber as the low recoil disturbs your sight picture less allowing you to better spot your impacts and your misses, and allowing for faster more accurate follow up shots.
For hunting bullets that need enough speed to expand properly to ensure significant hydraulic shock, the loss of speed from using a very short barrel can be problematic. My hunting rifles are 22-24”, while my targets guns are 26 and 30”.
For 6.5 Creedmoor, stability considerations only play a role if you select the Sierra 150 gn SMK, which requires a 7.5 twist. IMHO Sierra made a tactical mistake with their design, and Hornady and Berger designed their bullets correctly so they can stabilize in a standard 8 twist barrel. (Almost all existing 6.5 Creedmoor rifles are 8 twist).
But ever the optimist: I predict/hope that is going to change in the future and gun makers will move to 7.5 twist. And we might see high BC 6.5 mm target bullets around 160 to 170 grain. And yes they will have muzzle velocity similar to a 308.
That drop in speed does not matter as much as most people assume.
