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PAC-NOR

Selecting Barrel Twist Rates
      Our caliber and twist rate chart (see below) indicates the twist rate recommended for use with normally manufactured ammunition. Today's handloader, however, has access to a wide range of heavier and longer bullets; a faster rate of twist may be required to stabilize these bullets. For example, a 12" twistbarrel will stabilize a heavier or longer bullet than will a 14" twistbarrel. Basically, the twist rate you choose should be sufficient to stabilize the longest and heaviest bullets you plan to use.

Special Barrel Configurations
      PAC-NOR has the capability to make barrels with special requirements such as twist, rifling configuration, and bore and groove dimensions. We have made barrels for various ballistic labs, and arms and ammunition manufacturers. Since most of the tooling must be specially made, this type of work is done only on a written quote basis. Please supply us with drawings for your requirements by mail or fax so that we may accurately process your quote.

Caliber and Twist Rate Chart

Highlighted numbers are standard or popular twist rates.
17 (.172")
3 groove
9"
10"
4 groove
6"
7"
8"
9"
5 groove
10"
12"
Polygonal
7"

19 (.198")
3 groove
12"
6 groove
9"
13"
Polygonal
11"

20 (.204")
3 groove
7"
8"
8.50"
9"
10"
11"
12"
14"
16"
Polygonal
11"

5.45 Russian (.220")
4 groove
7.70"
10"

22 Rimfire (.222")
3 groove
16"
5 groove
16"
17"
6 groove
6"
8"
10"
14"
16"
18"
20"
9 groove
16"
17"
Polygonal
16"

22 (.224")
3 groove
6"
6.50"
7"
8"
9"
10"
12"
13"
13.25"
13.50"
14"
16"
4 groove
7.50"
8"
8.60"
13"
16"
5 groove
7"
8"
9"
10"
12"
14"
15"
6 groove
7"
14"
7 groove
14"
Polygonal
6.50"
7"
8"
9"
12"
14"

228 (.228")
5 groove
8"
10"

.23 (.234")
5 groove
12"
14"

6mm (.243")
3 groove
7"
8"
9"
10"
11"
12"
13.25"
14"
4 groove
7.50"
8"
8.60"
13.75"
14"
5 groove
5"
6"
7"
9"
12"
13"
15"
16"
6 groove
9"
10"
Polygonal
8"
9"
10"

25 (.257")
3 groove
10"
12"
14"
4 groove
11"
5 groove
9"
10"
12"
6 groove
8"
14"
Polygonal
10"

6.5mm (.264")
3 groove
8"
8.50"
9"
10"
4 groove
8.60"
11"
5 groove
7"
8"
9"
12"
6 groove
10"
Polygonal
8"
8.50"
9"

270 (.277")
3 groove
10"
13"
5 groove
8"
10"
6 groove
10"
12"
Polygonal
10"

7mm (.284")
3 groove
8"
9"
10"
11"
12"
13"
14"
15"
5 groove
7"
8"
9"
9.50"
9.52"
10"
6 groove
9.52"
11"
12"
14"
Polygonal
8"
9"
10"

.29 cal (.298")
5 groove
10"

.298 (30 Tight Bore) (.307")
4 groove
13"

30 (.308")
2 groove
16"
3 groove
6"
6.50"
7"
7.50"
9"
10"
12"
13"
14"
15"
4 groove
10"
11"
5 groove
4"
7"
8"
9"
10"
11"
12"
13"
15"
17"
18"
6 groove
8"
14"
Polygonal
8"
10"
12"

303 British (.311")
5 groove
10"

32-40 (.321")
5 groove
16"

8mm (.323")
3 groove
10"
5 groove
9"
10"
12"

338 (.338")
3 groove
6"
10"
11"
12"
14"
5 groove
6.50"
7"
9"
9.50"
10"
12"
6 groove
7"
Polygonal
8"
10"

348 (.348")
5 groove
12"

9mm (.355")
5 groove
12"
6 groove
14"

357 Pistol (.357")
Polygonal
14"

35 (.358")
5 groove
12"
6 groove
10"
14"
16"

9.3mm (.366")
5 groove
12"

375 (.375")
3 groove
12"
15"
5 groove
8"
12"
6 groove
10"
14"
15"
18"
Polygonal
10"

10mm (.400")
6 groove
16"
8 groove
8"
Polygonal
25"

408 (.408")
6 groove
16"
8 groove
13"

411 (.410")
8 groove
16"

405 (.412")
8 groove
14"

416 (.416")
3 groove
14"
6 groove
10"
12"
14"
8 groove
8"
11"
14"

404 (.423")
3 groove
9"
9 groove
14"

44 Pistol (.429")
8 groove
18"
25"
38"

425 WR (.435")
8 groove
16"

45 Pistol (.451")
6 groove
7"
16"
18"
22"
8 groove
36"

458 Rifle (.458")
3 groove
13"
14"
6 groove
8"
8 groove
10"
14"
15"
18"
20"
22"
26"

475 (.475")
6 groove
10"
16"
38"
8 groove
18"

50 cal - 50 A&E - 500 SW (.500")
3 groove
9"
8 groove
12"
18"
25"
36"

505 cal (.505")
8 groove
16"
20"

50 (.510")
3 groove
9"
6 groove
18"
20"
8 groove
9"
14"

50 BMG (.510")
3 groove
13"
15"
26"
38"
8 groove
10"
13"
14"
15"
20"
Polygonal
15"

50 Muzzle Loader (.510")
6 groove
20"

550 (.550")
7 groove
16"
20"

577 (.585")
9 groove
18"

600 Nitro (.620")
3 groove
20"
9 groove
16"
20"
36"

.685 (.685")
9 groove
20"

700 Nitro (.700")
9 groove
20"

705 (.705")
8 groove
36"

12 ga. (.729")
7 groove
20"

20mm (.825")
9 groove
20"



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