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Twist rate & bullet stability Long, heavy-for-caliber bullets need a fast twist to fly point-first. This calculator uses the Miller twist rule to give a gyroscopic stability factor (SG) for your bullet in your barrel, and tells you the twist it would take to reach full stability.
Pick a bullet from our cartridge reference (or type your own) Choose a bullet… 22-250 Remington — Hornady 35 gr V-MAX 223 Remington — Nosler 40 gr Ballistic Tip Varmint 22-250 Remington — Nosler 40 gr Ballistic Tip Varmint 22-250 Remington — Sierra 50 gr BlitzKing 22-250 Remington — Hornady 53 gr V-MAX 223 Remington — Hornady 55 gr V-MAX 223 Remington — Sierra 55 gr BlitzKing 22-250 Remington — Sierra 55 gr Varminter SPT 22-250 Remington — Nosler 55 gr Ballistic Tip Varmint 223 Remington — Nosler 60 gr Partition 22-250 Remington — Hornady 60 gr V-MAX 22-250 Remington — Nosler 60 gr Partition 223 Remington — Barnes 62 gr TTSX BT 223 Remington — Hornady 62 gr ELD-VT 223 Remington — Sierra 69 gr MatchKing HPBT 223 Remington — Hornady 75 gr ELD Match 223 Remington — Sierra 77 gr MatchKing HPBT 243 Winchester — Hornady 58 gr V-MAX 243 Winchester — Nosler 70 gr Ballistic Tip Varmint 243 Winchester — Barnes 85 gr TTSX BT 243 Winchester — Sierra 85 gr GameKing HPBT 243 Winchester — Nosler 95 gr Ballistic Tip 243 Winchester — Hornady 95 gr SST 243 Winchester — Sierra 100 gr GameKing SBT 243 Winchester — Hornady 103 gr ELD-X 243 Winchester — Berger 105 gr Hybrid Target 6.5 Creedmoor — Hornady 120 gr ELD Match 6.5 Creedmoor — Barnes 127 gr LRX BT 6.5 PRC — Barnes 127 gr LRX BT 6.5 Creedmoor — Berger 130 gr AR Hybrid OTM Tactical 6.5 PRC — Hornady 130 gr CX 6.5 Creedmoor — Hornady 140 gr ELD Match 6.5 Creedmoor — Sierra 140 gr MatchKing HPBT 6.5 Creedmoor — Berger 140 gr Hybrid Target 6.5 Creedmoor — Nosler 140 gr AccuBond Long Range 6.5 PRC — Hornady 140 gr ELD Match 6.5 PRC — Sierra 140 gr MatchKing HPBT 6.5 PRC — Nosler 142 gr AccuBond Long Range 6.5 Creedmoor — Hornady 143 gr ELD-X 6.5 PRC — Hornady 143 gr ELD-X 6.5 Creedmoor — Hornady 147 gr ELD Match 6.5 PRC — Hornady 147 gr ELD Match 6.5 PRC — Berger 156 gr EOL Elite Hunter 270 Winchester — Hornady 100 gr SP 270 Winchester — Nosler 130 gr AccuBond 270 Winchester — Sierra 130 gr GameKing SBT 270 Winchester — Barnes 130 gr TTSX BT 270 Winchester — Hornady 130 gr SST 270 Winchester — Speer 130 gr Hot-Cor SP 270 Winchester — Hornady 140 gr ELD-X 270 Winchester — Berger 140 gr Hybrid Hunter 270 Winchester — Nosler 150 gr Partition 7mm-08 Remington — Hornady 120 gr SST 7mm-08 Remington — Hornady 139 gr SST 7mm Remington Magnum — Hornady 139 gr SST 7mm-08 Remington — Nosler 140 gr AccuBond 7mm-08 Remington — Sierra 140 gr GameKing SBT 7mm-08 Remington — Barnes 140 gr TTSX BT 7mm Remington Magnum — Sierra 140 gr GameKing SBT 7mm-08 Remington — Speer 145 gr Grand Slam 7mm-08 Remington — Nosler 150 gr Partition 7mm Remington Magnum — Nosler 150 gr AccuBond 7mm Remington Magnum — Hornady 154 gr SST 7mm Remington Magnum — Barnes 160 gr TTSX BT 7mm-08 Remington — Hornady 162 gr ELD-X 7mm Remington Magnum — Hornady 162 gr ELD-X 7mm Remington Magnum — Berger 168 gr Elite Hunter 7mm Remington Magnum — Sierra 168 gr MatchKing HPBT 7mm Remington Magnum — Nosler 175 gr Partition 7mm Remington Magnum — Berger 180 gr Hybrid Target 300 AAC Blackout — Barnes 110 gr TAC-TX 300 AAC Blackout — Hornady 110 gr V-MAX 300 AAC Blackout — Barnes 120 gr Match Burner OTM 300 AAC Blackout — Sierra 125 gr HP 300 AAC Blackout — Hornady 125 gr SST 300 AAC Blackout — Sierra 125 gr MatchKing HPBT 30-30 Winchester — Hornady 150 gr RN InterLock 30-30 Winchester — Winchester 150 gr Power-Point FN 300 AAC Blackout — Nosler 150 gr Ballistic Tip 308 Winchester — Hornady 150 gr SST 308 Winchester — Speer 150 gr Hot-Cor SP 30-06 Springfield — Hornady 150 gr SST 30-06 Springfield — Speer 150 gr Hot-Cor SP 300 Winchester Magnum — Hornady 150 gr SST 30-30 Winchester — Hornady 160 gr FTX 308 Winchester — Nosler 165 gr AccuBond 30-06 Springfield — Nosler 165 gr AccuBond 300 Winchester Magnum — Barnes 165 gr TTSX BT 308 Winchester — Sierra 168 gr MatchKing HPBT 308 Winchester — Hornady 168 gr ELD Match 308 Winchester — Barnes 168 gr TTSX BT 30-06 Springfield — Sierra 168 gr MatchKing HPBT 30-06 Springfield — Barnes 168 gr TTSX BT 30-30 Winchester — Hornady 170 gr FP InterLock 30-30 Winchester — Sierra 170 gr FN Pro-Hunter 30-30 Winchester — Speer 170 gr Hot-Cor FN 30-30 Winchester — Remington 170 gr Core-Lokt SP 30-30 Winchester — Federal 170 gr Fusion RN 308 Winchester — Sierra 175 gr MatchKing HPBT 308 Winchester — Berger 175 gr OTM Tactical 30-06 Springfield — Berger 175 gr OTM Tactical 308 Winchester — Hornady 178 gr ELD-X 30-06 Springfield — Hornady 178 gr ELD-X 300 Winchester Magnum — Nosler 178 gr AccuBond Long Range 300 Winchester Magnum — Hornady 178 gr ELD-X 30-06 Springfield — Sierra 180 gr GameKing SBT 300 Winchester Magnum — Berger 185 gr Juggernaut OTM Elite Hunter 300 Winchester Magnum — Sierra 190 gr MatchKing HPBT 300 Winchester Magnum — Nosler 200 gr Partition 300 Winchester Magnum — Hornady 200 gr ELD Match 300 AAC Blackout — Hornady 208 gr A-MAX 300 AAC Blackout — Sierra 220 gr MatchKing HPBT 30-06 Springfield — Nosler 220 gr Partition 30-06 Springfield — Hornady 220 gr InterLock RN 300 Winchester Magnum — Sierra 220 gr MatchKing HPBT 7.62x39 — Hornady 123 gr SST 7.62x39 — Hornady 123 gr FMJ 7.62x39 — Speer 123 gr Hot-Cor SP 7.62x39 — Hornady 123 gr A-MAX 7.62x39 — Sierra 125 gr Pro-Hunter SPT 7.62x39 — Barnes 125 gr TSX 7.62x39 — Hornady 150 gr InterLock SP 7.62x39 — Sierra 150 gr Pro-Hunter SPT 8.6 Blackout — Barnes 210 gr TTSX BT 8.6 Blackout — Hornady 225 gr CX 8.6 Blackout — Barnes 250 gr TSX FB 8.6 Blackout — Discreet Ballistics 280 gr Selous Machined Expander 8.6 Blackout — Barnes 285 gr TSX BT 8.6 Blackout — Berger 300 gr Hybrid OTM Tactical 8.6 Blackout — Nosler 300 gr AccuBond Long Range 8.6 Blackout — Hornady 307 gr Sub-X 8.6 Blackout — Maker 350 gr REX (Rapid Expanding) 9mm Luger — Lehigh Defense 90 gr Xtreme Defender 9mm Luger — Hornady 115 gr XTP 9mm Luger — Hornady 115 gr FTX Critical Defense 9mm Luger — Hornady 124 gr XTP 9mm Luger — Speer 124 gr Gold Dot HP 9mm Luger — Berry's 124 gr HBRN-TP 9mm Luger — Xtreme 124 gr Plated RN 357 SIG — Hornady 124 gr XTP 357 SIG — Sierra 124 gr Sports Master JHP 357 SIG — Xtreme 124 gr Plated RN 9mm Luger — Sierra 125 gr HAP 357 SIG — Hornady 125 gr XTP 357 SIG — Speer 125 gr Gold Dot HP 357 SIG — Berry's 125 gr HBRN-TP 357 SIG — Hornady 135 gr FTX Critical Duty 9mm Luger — Hornady 147 gr XTP 357 SIG — Hornady 147 gr XTP 380 Automatic — Lehigh Defense 68 gr Xtreme Defender 380 Automatic — Hornady 90 gr XTP 380 Automatic — Hornady 90 gr FTX Critical Defense 380 Automatic — Speer 90 gr Gold Dot HP 380 Automatic — Sierra 95 gr Sports Master JHP 380 Automatic — Hornady 95 gr FMJ-RN 380 Automatic — Berry's 95 gr RN Plated 380 Automatic — Xtreme 95 gr Plated RN 38 Special — Lehigh Defense 105 gr Xtreme Defender 38 Special — Hornady 110 gr FTX Critical Defense 38 Special — Hornady 125 gr XTP 357 Magnum — Hornady 125 gr XTP 38 Special — Speer 135 gr Gold Dot Short Barrel 357 Magnum — Hornady 140 gr FTX 357 Magnum — Barnes 140 gr XPB 38 Special — Hornady 148 gr HBWC 38 Special — Sierra 158 gr JHC Sports Master 38 Special — Hornady 158 gr XTP 38 Special — Berry's 158 gr Round Nose (plated) 38 Special — Bayou Bullets 158 gr Coated SWC 357 Magnum — Hornady 158 gr XTP 357 Magnum — Speer 158 gr Gold Dot 357 Magnum — Nosler 158 gr JHP 357 Magnum — Berry's 158 gr Round Nose (plated) 357 Magnum — Bayou Bullets 158 gr Coated SWC 357 Magnum — Sierra 170 gr JHC Sports Master 357 Magnum — Hornady 180 gr XTP 40 Smith & Wesson — Lehigh Defense 115 gr Xtreme Defender 40 Smith & Wesson — Hornady 135 gr FlexLock 10mm Automatic — Lehigh Defense 140 gr Xtreme Penetrator 40 Smith & Wesson — Hornady 155 gr XTP 10mm Automatic — Barnes 155 gr TAC-XP 40 Smith & Wesson — Hornady 165 gr XTP 40 Smith & Wesson — Hornady 180 gr XTP 40 Smith & Wesson — Speer 180 gr Gold Dot HP 40 Smith & Wesson — Sierra 180 gr Sports Master JHP 40 Smith & Wesson — Nosler 180 gr JHP 40 Smith & Wesson — Berry's 180 gr Plated RN 40 Smith & Wesson — Bayou Bullets 180 gr Coated FP 10mm Automatic — Hornady 180 gr XTP 10mm Automatic — Federal 180 gr HST 10mm Automatic — Sierra 180 gr Sports Master JHP 10mm Automatic — Xtreme 180 gr Plated RN 10mm Automatic — Bayou Bullets 180 gr Coated RN 10mm Automatic — Hornady 200 gr XTP 10mm Automatic — Speer 200 gr Gold Dot HP 10mm Automatic — Cast Performance 220 gr WFNGC hard-cast 44 Remington Magnum — Hornady 180 gr XTP 44 Remington Magnum — Hornady 200 gr XTP 44 Remington Magnum — Hornady 225 gr FTX 44 Remington Magnum — Barnes 225 gr XPB 44 Remington Magnum — Hornady 240 gr XTP 44 Remington Magnum — Hornady 300 gr XTP 45 Automatic — Lehigh Defense 155 gr Xtreme Defender 45 Automatic — Hornady 185 gr XTP 45 Automatic — Hornady 200 gr HAP 45 Automatic — Speer 200 gr Gold Dot G2 45 Automatic — Bayou Bullets 200 gr Coated SWC 45 Automatic — Hornady 230 gr XTP 45 Automatic — Speer 230 gr Gold Dot HP 45 Automatic — Federal 230 gr HST 45 Automatic — Xtreme 230 gr Plated RN 45 Colt — Barnes 200 gr XPB 45 Colt — Hornady 225 gr FTX 45 Colt — Hornady 250 gr XTP 45 Colt — Hornady 255 gr FP Cowboy 45 Colt — Hornady 300 gr XTP 45-70 Government — Hornady 250 gr MonoFlex 45-70 Government — Hornady 300 gr RN InterLock 45-70 Government — Speer 300 gr HP 45-70 Government — Barnes 300 gr Original FN 45-70 Government — Hornady 325 gr FTX 45-70 Government — Hornady 350 gr RN InterLock 45-70 Government — Speer 400 gr Hot-Cor FN 45-70 Government — Remington 405 gr SP Stability factor SG = 2.46 Fully stable — full BC. This is the range to aim for. For SG 1.5 this bullet wants 1:12.8" or faster; it goes unstable slower than 1:15.7". Air at 29.92 inHg.
Reading SG Below 1.0 — unstable; the bullet tumbles.1.0–1.3 — marginal. It may fly at the range in July and keyhole in January, because cold, dense air lowers SG.1.3–1.5 — stable, with a small BC penalty (roughly 3% per 0.1 SG below 1.5). Plenty for hunting.1.5 and up — fully stable, full BC. This is the target for long-range work.How it works and where it's approximate Don Miller's 2005 rule improved on Greenhill's by using bullet weight, length and diameter together, with corrections for velocity (¹⁄₃ power) and air density. It is a formula for conventional lead-core, jacketed bullets. Two known gaps:
Plastic tips add length without adding mass, which makes the rule pessimistic. Ticking the box uses an effective length of 90% of the measured length, a common working correction; for a published figure, use the bullet maker's own recommended twist.Solid copper / monolithic bullets are longer for their weight and the rule tends to undercall the twist they need. Trust the maker's minimum twist over this number.Bullet lengths in the preset list come from our cartridge reference ; the velocity that fills in is the SAAMI nominal for that bullet weight, so change it to your chronographed number. At Denver's 5,280 ft the thinner air adds about 0.2 SG compared with sea level — set your altitude.
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