Bore, Groove and Twist Specifications

The specifications below are drawn from CIP, SAAMI and other sources and are the guidelines we use for manufacturing our bullets. If your rifle has been rebarrelled, check with the supplier of the new barrel whether the barrel conforms to the original specification. Examples of errors that can occur would be to replace a 7x57 or 7x64 barrel with a 7mm Rem Mag barrel. We have seen 404 rifles with .423 barrels as well as .418 barrels, 6.5 Swedish Mausers with .264 Win Mag barrels and so on. The Case Length column contains the maximum case length.  The trim length is shorter and varies according to the caliber.

Twist Rate By Manufacturer

Caliber Bore mm Groove mm Twist mm Case Length mm Bore Inches Groove Inches Twist Inches Case Length Inches
177 Rem 4.270 4.370 229 45.62 0.168 0.172 9.0 1.79
.204 5.029 5.169 305 47.24 0.1980 0.2035 12.0 1.85
5mm Rem Mag 5.070 5.190 305 N/A 0.1996 0.2043 12.0 N/A
5.6 x 35R 5.350 5.580 360 35.5 0.211 0.220 14.2 1.40
22LR 5.380 5.580 406 N/A 0.212 0.220 16.0 N/A
22 Hornet 5.510 5.640 406 35.64 0.217 0.222 16.0 1.40
22 PPC USA 5.530 5.660 355 38.48 0.218 0.223 14.0 1.52
5.6x57 5.540 5.690 250 56.70 0.218 1.224 9.8 2.23
5.6x57R 5.540 5.690 250 56.70 0.218 0.224 9.8 2.23
224 Wea Mag 5.540 5.690 356   0.218 0.224 14.0  
223 Rem 5.560 5.690 305 44.70 0.219 0.224 12.0 1.760
5.6x50Mag 5.560 5.690 350 50.00 0.219 0.224 13.8 1.97
5.6x50Mag/R 5.560 5.690 350   0.219 0.224 13.8  
220 Swift 5.560 5.690 356   0.219 0.224 14.0  
222 Rem 5.560 5.690 356   0.219 0.224 14.0  
22-250 5.560 5.690 356   0.219 0.224 14.0  
219 Zipper 5.560 5.690 406   0.219 0.224 16.0  
5.6x61 SE v H 5.580 5.760 220 61.00 0.220 0.227 8.66 2.40
22 Sav 5.610 5.740 305   0.221 0.226 12.0  
240 Wea Mag 6.020 6.170 254   0.237 0.243 10.0  
243 Win 6.020 6.170 254 51.94 0.237 0.243 10.0 2.049
244 H&H 6.020 6.220 255   0.237 0.245 10.0  
25-35 6.350 6.500 203   0.250 0.256 8.0  
25-06 6.350 6.530 254 63.35 0.250 0.257 10.0 2.494
250 Sav 6.350 6.530 356 48.56 0.250 0.257 14.0 1.912
257 Wea Mag 6.360 6.530 254 64.75 0.250 0.257 10.0 2.549
6.5x65RWS 6.450 6.700 200 65.00 0.254 0.264 7.9 2.56
6.5x57 6.450 6.700 200 65.70 0.254 0.264 7.9 2.59
6.5x68 6.450 6.700 250 67.50 0.254 0.264 9.8 2.66
260 Rem 6.500 6.710 229 51.69 0.256 0.264 9.0 2.035
264 Win Mag 6.500 6.710 229   0.256 0.264 9.0  
6.5x55 Sw Mau 6.500 6.730 220 55.00 0.256 0.265 8.7 2.17
Caliber Bore mm Groove mm Twist mm Case Length mm Bore Inches Groove Inches Twist Inches Case Length Inches
6.5x54 M Sch 6.480 6.780 200 53.65 0.255 0.267 7.9 2.112
270 Win 6.860 7.040 254 64.52 0.270 0.277 10.0  
270 Wea Mag 6.870 7.040 254   0.270 0.277 10.0  
7mm Wea Mag 7.020 7.210 254   0.276 0.284 10.0  
7mm Rem Mag 7.040 7.210 241   0.277 0.284 9.5  
7-08 7.040 7.210 241   0.277 0.284 9.5  
280 Rem 7.040 7.210 254   0.277 0.284 10.0  
7x61 Super 7.000 7.220 229   0.276 0.284 9.0  
7x57 6.980 7.240 220 57.00 0.275 0.285 8.7 2.244
7x64 6.980 7.240 220 64.00 0.275 0.285 8.7 2.520
275 HV Rigby 6.970 7.250 203   0.274 0.285 8.0  
275 Belted NE 7.040 7.280 255   0.277 0.287 10.0  
280 Ross 7.050 7.300 220   0.278 0.288 8.7  
7.5x55 Swiss 7.540 7.770 270 55.6 0.297 0.306 10.6 2.189
300 Lapua Mag 7.620 7.820 240   0.300 0.308 9.4  
300 H&H 7.610 7.820 254   0.300 0.308 10.0  
300 Win Mag 7.620 7.820 254   0.300 0.308 10.0  
308 Norma 7.620 7.820 254   0.300 0.308 10.0  
30-06 7.620 7.820 254   0.300 0.308 10.0  
30 R Blaser 7.620 7.820 305   0.300 0.308 12.0  
308 Win 7.620 7.820 305 51.18  0.300 0.308 12.0 2.015
30-30 Win 7.620 7.820 305   0.300 0.308 12.0  
300 Wea Mag 7.630 7.820 254   0.300 0.308 10.0  
300 Sav 7.620 7.820 305   0.300 0.308 12.0  
7.62x39 7.620 7.920 240 38.70 0.300 0.312 9.4 1.524
7.62x54R 7.620 7.920 240   0.300 0.312 9.4  
303 BR 7.700 7.980 254   0.303 0.314 10.0   
8x57J 7.800 8.070 240   0.307 0.318 9.4  
8x64 7.800 8.070 240   0.307 0.318 9.4  
8x64S 7.890 8.200 240   0.311 0.323 9.4  
8x68S 7.890 8.200 280   0.311 0.323 11.0  
Caliber Bore mm Groove mm Twist mm Case Length mm Bore Inches Groove Inches Twist Inches Case Length Inches
8mm Rem Mag 8.000 8.200 254   0.315 0.323 10.0  
8x57JS 7.890 8.200 240   0.311 0.323 9.4  
8x60S 7.890 8.200 240   0.311 0.323 9.4  
318 WR 8.070 8.380 305   0.318 0.330 12.0  
318 Rimless NE 8.070 8.380  305   0.318 0.330 12.0   
338 Lapua Mag 8.380 8.580 254   0.330 0.338 10.0  
8.5x64 8.380 8.590 254   0.330 0.338 10.0  
340 Wea Mag 8.380 8.590 254   0.330 0.338 10.0  
338 Win Mag 8.380 8.590 254   0.330 0.338 10.0  
350 Mag Rigby 8.890 9.060 305   0.350 0.357 12.0  
9x57 8.780 9.060 360   0.346 0.357 14.2  
35 Winchester 8.890 9.090 355   0.349 0.357 16.0  
35 Remington 8.890 9.090 406   0.349 0.357 16.0  
35 Whelen 8.860 9.070 406   0.349 0.357 16.0  
350 RemMag 8.860 9.070 406   0.349 0.357 16.0  
358 Norma 8.890 9.100 305   0.350 0.358 12.0  
9.3x64 9.000 9.280 360   0.354 0.365 14.2  
9.3x62 9.000 9.280 360   0.354 0.365 14.2  
9.3x57 9.000 9.280 360   0.354 0.365 14.2  
9.5x57 M.-Sch. 9.270 9.620 300   0.365 0.379 11.8  
375 Wea Mag 9.350 9.530 305   0.368 0.375 12.0  
378 Wea Mag 9.320 9.530 305   0.367 0.375 12.0  
375H&H 9.300 9.550 305   0.366 0.376 12.0  
.375 WR 9.300 9.550 305   0.366 0.376 12.0  
9.5x66 SEvH 9.300 9.550 305   0.366 0.376 12.0  
408 Win 10.150 10.330 356   0.400 0.407 14.0  
408 Chey-Tac 10.185 10.363 330   0.401 0.408 13.0  
450/400 N.E. 3" 10.160 10.410 381   0.400 0.410 15.0  
405 Win 10.290 10.490 356   0.405 0.413 14.0  
Caliber Bore mm Groove mm Twist mm Case Length mm Bore Inches Groove Inches Twist Inches Case Length Inches
416 Rem Mag 10.360 10.570 356 72.39 0.408 0.416 14.0 2.85
416 Wea Mag 10.360 10.570 356 73.99 0.408 0.416 14.0 2.91
416 Rigby 10.360 10.570 420 73.66 0.408 0.416 16.5 2.90
404 Jeffery 10.410 10.620 420   0.410 0.418 16.5  
404 Rimless NE 10.410 10.620 420   0.410 0.418 16.5  
10.75x68 10.450 10.750 420   0.411 0.423 16.5  
444 Marlin 10.770 10.920 965   0.424 0.430 38.0  
45-70 11.430 11.580 508   0.450 0.456 20.0  
450 Rigby 11.430 11.630 420   0.450 0.458 16.5  
460 Wea Mag 11.430 11.630 406   0.450 0.458 16.0  
458 Win Mag 11.430 11.630 356   0.450 0.458 14.0  
470 NE 11.850 12.050 533   0.467 0.474 21.0  
475No2NE31/2" 12.060 12.370 457   0.475 0.487 18.0  
505 Gibbs 12.550 12.800 406   0.494 0.504 16.0  
50 BMG 12.690 12.940 250   0.500 0.509 9.8  
50 BMG 12.690 12.940 381   0.500 0.509 15.0  
12.7x70 Sch 12.700 12.940 450   0.500 0.509 17.7  
500 Jeff 12.700 12.970 508   0.500 0.510 20.0  
500 N.E. 3" 12.700 13.000 381   0.500 0.512 15.0  
550 Magnum 13.720 13.970 457   0.540 0.550 18.0  
577 Snider 14.230 14.580 508   0.560 0.574 20.0  
577 NE 14.550 14.780 762   0.573 0.582 30.0  
600NE 15.340 15.570 762   0.604 0.613 30.0  
700NE 17.480 17.780 737   0.688 0.700 29.0  

GS Custom Bullets, situated in Port Elizabeth on the East Coast of South Africa, manufactures solid copper, turned, monolithic bullets for hunting and sport shooting. These bullets are used by hunters on several continents, hunting from the smallest of antelope to the largest of dangerous game, using the smooth HP bullet, as well as the more popular HV, FN and SP bullets with the patented drive band concept. GSC bullets are configured for the highest possible ballistic coefficients. SP bullets are mainly used for sport shooting. All GS Custom Bullets are coated.