I see the Zastavas in 6.5x55 have a 1:9.06" twist and CZs have a 1:8.66".
The first Swedish military rifles had a 1 in 7.87" twist and Tikka, SAKO, Ruger and some others have a faster 1:8" twist.
I looked up some bullet lengths and put them into the stability calculator on Berger's site using a 1:9" twist.
These bullets were fine:
Hornady 160 gr Interlock = 1.257" ✓
Military 156 gr bullet = 1.260" ✓
Sierra 140 gr GameKing = 1.262" ✓
Norma 156 gr Oryx = 1.283" ✓
Nosler 140 gr Partition = 1.290" ✓
Hornady 140 gr SST = 1.322" ✓
These ones were not:
Nosler 140 AccuBond = 1.368" x
Sierra 142 MatchKing = 1.375 x
Woodleigh 160 gr PP = 1.381" x
Berger 140 VLD = 1.421" x
So according to the calculator most bullets are a-okay including the old round nose designs.
But on the other hand, I've seen a lot of comments about how using the heavy 160 gr bullets in a 1:9 twist is marginal at best, and at worst a 1:9 won't even stabilize 140s very well.
Anybody have any experience with heavier bullets in a 1:9"?
The first Swedish military rifles had a 1 in 7.87" twist and Tikka, SAKO, Ruger and some others have a faster 1:8" twist.
I looked up some bullet lengths and put them into the stability calculator on Berger's site using a 1:9" twist.
These bullets were fine:
Hornady 160 gr Interlock = 1.257" ✓
Military 156 gr bullet = 1.260" ✓
Sierra 140 gr GameKing = 1.262" ✓
Norma 156 gr Oryx = 1.283" ✓
Nosler 140 gr Partition = 1.290" ✓
Hornady 140 gr SST = 1.322" ✓
These ones were not:
Nosler 140 AccuBond = 1.368" x
Sierra 142 MatchKing = 1.375 x
Woodleigh 160 gr PP = 1.381" x
Berger 140 VLD = 1.421" x
So according to the calculator most bullets are a-okay including the old round nose designs.
But on the other hand, I've seen a lot of comments about how using the heavy 160 gr bullets in a 1:9 twist is marginal at best, and at worst a 1:9 won't even stabilize 140s very well.
Anybody have any experience with heavier bullets in a 1:9"?
