Best match bullet for a 1:12.25 twist?
- Thread starter MarkFenn
- Start date
That twist (although odd) will pretty much work fine with any 308 grain bullet that you would ever want to shoot from a 308 win cartridge. You might start to see things fall apart with bullets above 190 grains but less than that will be just fine. if you want great match type bullet, the 185 Berger juggernaught would be fantastic, and so would their 155.5 grain fullbore bullet. Each gun is different and may not like all bullets, but don't feel your twist will be a limiting factor. experiment, have fun.
- Location
- Halifax, NS
For all your long range calculation needs there's JBM:
http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi
Stability is mainly a factor of bullet length, MV, atmospherics, and twist, not so much about weight. Because of this, if you're going to shoot the real heavy projectiles, try to shoot ones with shorter OALs such as the Berger Boat Tails (BT) instead of the VLDs. The VLDs use a secant ogive and are longer (higher BC) but the BTs use a tangent ogive (most common type) making them shorter and less aerodynamic, but easier to stabilize.
Stability factor of 1.2 is ideal (not too high nor too low). In a typical Toronto atmosphere in the spring/summer, for a Berger 185 hybrid (very long) @ 2500fps, you're looking at a stability factor of 1.15. Should be ok. For the Berger 185 'Juggernaut' (aka BT) at the same 2500fps you're looking at 1.41 (goes down to 1.10 at -20 Celsius and high pressure), no dramas there! For a Berger 168 BT (shorter) in the same atmosphere at 2630 fps (roughly the same pressure), stability factor is 1.76, arguably too high.
Have no fear using the 185s. For something heavier, pick the shorter version and avoid shooting in the winter/low density altitudes.
http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi
Stability is mainly a factor of bullet length, MV, atmospherics, and twist, not so much about weight. Because of this, if you're going to shoot the real heavy projectiles, try to shoot ones with shorter OALs such as the Berger Boat Tails (BT) instead of the VLDs. The VLDs use a secant ogive and are longer (higher BC) but the BTs use a tangent ogive (most common type) making them shorter and less aerodynamic, but easier to stabilize.
Stability factor of 1.2 is ideal (not too high nor too low). In a typical Toronto atmosphere in the spring/summer, for a Berger 185 hybrid (very long) @ 2500fps, you're looking at a stability factor of 1.15. Should be ok. For the Berger 185 'Juggernaut' (aka BT) at the same 2500fps you're looking at 1.41 (goes down to 1.10 at -20 Celsius and high pressure), no dramas there! For a Berger 168 BT (shorter) in the same atmosphere at 2630 fps (roughly the same pressure), stability factor is 1.76, arguably too high.
Have no fear using the 185s. For something heavier, pick the shorter version and avoid shooting in the winter/low density altitudes.
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