Calibers and Twist Rates

Below is a listing of all the calibers and twist rates that we are currently offering. Some twists are available in more than one groove configuration as indicated.

Caliber	Twist Rate in Inches & Number of Grooves
.172 (.17)	6″ 4-G, 7″ 4-G, 9″ 4-G, 6-G 10″ 4-G
.177 (airgun)	17″ 4-G, 26″ 3-G, 32″ 3-G 40” 4-G
4.6 mm	6″ 4-G, 7” 6-G
.204 (.20, 5mm)	7″ 3-G, 9″ 3-G, 11″ 3-G, 12″ 3-G
.22 RF	7″ 3-G, 9″ 3-G, 15″ 6-G, 16″ 3-G 4-G 6-G, 17″ 4-G
.224 (.22)	7″ 3-G 6-G, 8″ 3-G 4-G 6-G, 9″ 6-G, 10″ 6-G, 12″ 3-G 6-G, 14″ 3-G 6-G, 15″ 3-G 6-G
.226(.22HP)	14″ 6-G
.234	10″ 6-G
.243 (6mm)	7″ 3-G, 7.5” 4-G 8″ 3-G, 4-G, 5-G 9″ 3-G 6-G, 10″ 3-G 6-G, 12″ 3-G 6-G, 13″ 3-G 6-G, 14″ 3-G 6-G, 15″ 3-G 6-G,
.257 (.25)	7″ 3-G, 8″ 3-G, 10″ 3-G 6-G, 12″ 6-G, 13″ 6-G, 14″ 6-G
.264 (6.5mm)	7.5″ 3-G, 8″ 3-G, 4-G, 5-G, 6-G, 9″ 6-G, 10″ 6-G, 12″ 6-G
.277 (.270)	7” 3-G, 8″ 3-G, 10″ 3-G 4-G 6-G, 12″ 6-G
6.8 mm	10″ 3-G 6-G
.284 (7mm)	7″ 3-G, 8″ 3-G, 9″ 3-G 4-G 6-G, 10″ 6-G, 12″ 6-G, 14″ 6-G
7.5 mm (.305)	11″ 4-G
.308 (.30)	7″ 3-G, 8″ 3-G 6-G, 9″ 3-G 6-G, 10″ 3-G 4-G 5R 6-G, 11″ 3-G 6-G, 12″ 3-G 4-G 6-G, 13″ 6-G, (3-G, 8-G .299″ bore only), 14″ 4-G 6-G, 15″ 3-G 6-G, 16″ 6-G, 17″ 3-G
.311 (.3105)	7″ 6-G, 10″ 4-G
.323 (8 mm)	10″ 6-G
.338	7″ 6-G, 9″ 6-G, 10″ 6-G, 12″ 6-G
.355 (9mm)	12” 5-G, 16” 6-G
.358 (.35)	9″ 6-G, 10″ 6-G, 12″ 6-G, 16″ 6-G
9.3mm (.366)	12″ 6-G
.375	8″ 6-G, 9″ 6-G, 10″ 6-G, 12″ 6-G
.408 (.40)	13″ 5-G, 6-G, 16″ 6-G
.416	9″ 6-G, 10″ 6-G, 11″ 6-G, 12″ 8-G, 13″ 6-G, 14″ 8-G
.423 (.404 Jeffery)	14″ 6-G
.425 W-R (.435)	16″ 6-G
.458 (.45)	9″ 6-G, 10″ 6-G, 12” 6-G. 14″ 8-G, 16” 5-G 20″ 6-G, 48″ 6-G
.510 (.50)	13″ 6-G, 15″ 4-G, 6-G, 7-G, 26″ 8-G, 32″ 6-G, 48″ 6-G

Long Barrels

Our standard length barrels are furnished as a 28″ long blank that will finish up to 27″. Most caliber/twist combinations can be ordered in a finish length up to 30″ at an additional charge.

Only the following caliber/twist combinations can be ordered over 30″ in length. Maximum finish length is 44″ unless indicated otherwise.

Caliber	Twist	Grooves	Max. Length


6mm	7 & 8	3	36″
6.5mm	8	3	36″
7mm	7	3	36″
	9	4	36″
.308	8	3	44″
	9	3	44″
	10	3
	10	6	44″
	11	3	44″
	13	3	34″ W/.299″ bore only
.338	7, 9 & 10	6	44″
.358	9, 10 &12	6	44″
.375	8, 9 & 10	6	44″
.408	13	5, 6	44″
.416	9	6	44″
	10	6	44″
	11	6	44″
	12	8	44″
	13	6	44″
.435	16	6	44″
.458	9, 10, 12, 16	6	44″
.510	13 & 15	6,7	44″

Twist Selection

For help in selecting the correct twist rate for the bullet you plan to use please refer to the chart below. The rate should be based on the heaviest bullet you intend to use. We are also very willing to help you determine the correct twist. You may contact Carson with questions by e-mail CLICK HERE.

BULLET WEIGHT / CALIBER / TWIST RATE CHART

Grain/Cal	.172	.204	.224	.243	.257	.264	.277	.284	.308	.338	.358
17-20	9-10
25	10
30	9	12
33		12
35		12
37 VLD	6
40		11,12
50-52		9	14
55			12
60			12
68-69			9,10	13,14
75			9		14
80			8
85			7	12	12	12
90			7	10
100				10	10		12	14
105-107				8
120					10	9,10		12	15,16
130					8	8	10		14
140						8	10	10
150						7			14
140-160							10	10	12,13
150-168								9	11,12,13
168-180									10,11,12
160								9
175								9
180								8,9	10,11,12
190-195								8	10,11
200									10,11	10,12	12,16
220									9,10
225										10,12	12,16
240-250									8,9	10	12
300										9,10	12

The above chart is from our FAQ section. For more information about choosing the correct twist rate Click Here. This chart is based on jacketed lead-core bullets. With some monolithic and plastic-tipped bullets the above twists may be too slow. The reason for this is that copper and yellow-metal bullets are less dense than lead-core bullets and so with bullets of an equal weight the monolithic bullets are longer. And length has a lot of influence on twist required. The plastic tips on some bullets also add length without weight.

To read an article on bullet design and download a free program that calculates twist rate based on specific bullet dimensions Click Here