Compromised BC when using a slower twist barrel

[Methow Packer]

Guys wondering about the use of high BC bullets when you don't have a recommended fast twist barrel. According to the twist calculator a 270 cal 170 grain hybrid needs a 8" twist to stabilize properly. Using a 10" barrel the BC is compromised by 6%. Question is does this mean your accuracy is compromised 6%? Could I use this bullet at more moderate ranges and still achieve regular accuracy. Maybe 600-800 yards. The BC would be 318 instead of 338. The adjusted marginal sg is 1.3

 

[RockyMtnMT]

If you are punching targets you will probably be fine. My concern as a bullet maker is that marginal stability leads to a higher potential of bullet failure terminally. Terminal performance of bullets suffers as the sg goes down. Likewise bullet performance gets better as the sg goes up. It is my opinion through testing on media and game animals that an sg of 1.5 should be considered a minimum for hunting. I personally used to use bullets of marginal stability for hunting as they were highly accurate. There were times that I was not happy with bullet performance and chalked it up to a poorly designed bullet. It has been in the last couple of years of testing our own bullets before marketing them that I have learned the effects of twist on terminal performance.

Most bullets will fly accurately down to 1.1 to 1.2sg. It depends on the bullet. Some bullets can show accuracy issues at 1.3sg but I would guess that your accuracy will be good.

Steve

 

[Methow Packer]

If you are punching targets you will probably be fine. My concern as a bullet maker is that marginal stability leads to a higher potential of bullet failure terminally. Terminal performance of bullets suffers as the sg goes down. Likewise bullet performance gets better as the sg goes up. It is my opinion through testing on media and game animals that an sg of 1.5 should be considered a minimum for hunting. I personally used to use bullets of marginal stability for hunting as they were highly accurate. There were times that I was not happy with bullet performance and chalked it up to a poorly designed bullet. It has been in the last couple of years of testing our own bullets before marketing them that I have learned the effects of twist on terminal performance.

Most bullets will fly accurately down to 1.1 to 1.2sg. It depends on the bullet. Some bullets can show accuracy issues at 1.3sg but I would guess that your accuracy will be good.

Steve

Great reply. I got the info I was looking for. Helps me understand the big picture. Many Thanks

 

[tim_w]

No imo experience accuracy is fine as long as the bullet is stable vs ideal.

With hunting imo and experience it depends on what type of end perf you are looking for. If you want the bullet to track straight and hold together classic mushroom then more spin. If you want the bullet to upset i.e. yaw and tumble causing the bullet to break up and do damage that way then less spin. As most hunting bullets are meant to do the prior and if dealing with thick deep tissue depth game elk bear moose you want the prior for sure imo. For deer and any thin skinned predator game it has less effect.

But honestly there is no reason for use of early yaw bullet designs as they were created becuase of human fighting and rules of war.. Bullet design these days is so good noo reason for hunting.