Rifle Barrels: Calibers and Twists

[TXCOONDOG]

The information below will help you select the best barrel twist for your specific needs, providing of course there are multiple choices. If you'll be shooting one bullet weight, choose a twist from the chart just fast enough to stabilize it. Too fast a twist simply overspins the bullet and may result in reduced accuracy. On the other hand, a twist too slow for any bullet will likely produce instability, keyholing and rotten accuracy. So if you're going to be using several bullet weights, be sure to select a twist that will stabilize the heaviest one, since lighter bullets will also be stabilized.

By way of explanation, the numbers in the "Twist" column indicate how far the bullet must travel through the bore to make one full revolution. This is determined by the rate of rotation of the rifling. For example, a 9"-twist barrel spins the bullet one full turn when it passes 9 inches through the bore. In a 16"-twist barrel, the bullet makes one revolution in 16 inches. So at the same bullet velocity, the 9" twist is faster (spins the bullet faster) than the 16" twist. Consequently, as the chart reflects in the .224 CF section, the 9" twist is necessary for stabilizing heavier bullet weights.

Again looking at the .224 CF section, if you're planning to shoot 55-grain bullets, the 14" twist is ideal. This twist is also the best choice for 52- and 53-grain match bullets driven at moderate velocities. But if you're also contemplating shooting a 60-grainer, go with the 12" twist, since it will stabilize all the bullets you'll be using. As you can see from the 15" and 16" twists, higher velocities also spin the bullet faster and may enable a slower-than-recommended twist to stabilize a marginally overweight bullet. However, this is tricky stuff best left to those who are highly experienced in operating at the ragged edge of stability and sanity.

The basic principles just outlined apply to all the calibers below.
But, if you have questions or need a recommendation, post up!




Caliber Twist:


.172
- 9" for bullets heavier than 30gr.
- 10" for bullets up to 30gr.

.204/20
- 12" for all bullets


.222 RF
- 14"* Twist for pistol barrels
- 16" Standard twist for rifle barrels
- 17"* Special twist for rifle barrels

.224 CF
- 8" for bullets heavier than 70gr.
- 9" for bullets up to 70gr.
- 12: for bullets up to 63gr.
- 14" for bullets up to 55gr.
- 15"* for bullets up to 55gr. driven 4,100 pfs or more
- 16:* for bullets up to 55gr. driven 4,300 fps or more

6mm/.243
- 8" Special for VLD bullets over 100 gr.
- 10" For bullets up to 120 gr. and VLD under 100 gr.
- 12" for bullets up to 85gr.
- 13"* for bullets up to 75gr.
- 14"* for bullets up to 70gr.
- 15"* Special for bullets up to 70gr.

.257
- 9" for bullets heavier than 100gr.
- 10" for bullets up to 100gr.
- 12" for bullets up to 90gr.
- 13"* for bullets up to 80gr.
- 14"* for bullets up to 70gr.

6.5mm/.264
- 8" for bullets heavier than 130gr.
- 9" for bullets up to 130gr.

6.8 SPC I
-10" for bullets up to 130gr.

6.8 SPC II
-11" for bullets up to 130gr.
-11.25" for bullets up to 130gr.

.270
- 10" for all bullets

7mm/.284
- 9" for bullets heavier than 140gr.
- 11" for bullets up to 140gr.

.307
- 13"* Special size and twist

.308
- 8" for bullets heavier than 220gr.
- 10" for bullets up to 220gr.
- 12" for bullets up to 170gr.
- 14"* for bullets up to 168gr.
- 15"* for bullets up to 150gr.

7.65mm/.311
- 10" for all bullets

8mm/.323
- 10" for all bullets

.338
- 10" for all bullets


9mm/.355
- 14" for low velocity wad cutters
- 16" for all other bullets

.38/.357
- 14" for low velocity wad cutters
- 18" for all other bullets

.358
- 14" for all bullets

.375
- 12" for all bullets

10mm/.400
- 16" for all bullets

.411
- 14" for all bullets

.416
- 14" for all bullets

.44
- 20" for all bullets
- 16" for low velocity wad cutters

.451
- 16" for all bullets

.458
- 14" for all bullets


* Stainless Steel only



Black Powder Barrels (1.250" x 30"):


.32
- 14" .320 groove

.38
- 20" .379 groove

.40
- 20" .403 groove

.457
- 20" , 14" .457 groove

 

[TXCOONDOG]

Sinclair’s Simple Twist Rate Measurement Method:


If you are unsure of the twist rate of the barrel, you can measure it yourself in a couple of minutes. You need a good cleaning rod with a rotating handle and a jag with a fairly tight fitting patch. Utilize a rod guide if you are accessing the barrel through the breech or a muzzle guide if you are going to come in from the muzzle end. Make sure the rod rotates freely in the handle under load. Start the patch into the barrel for a few inches and then stop. Put a piece of tape at the back of the rod by the handle (like a flag) or mark the rod in some way. Measure how much of the rod is still protruding from the rod guide. You can either measure from the rod guide or muzzle guide back to the flag or to a spot on the handle. Next, continue to push the rod in until the mark or tape flag has made one complete revolution. Re-measure the amount of rod that is left sticking out of the barrel. Use the same reference marks as you did on the first measurement. Next, subtract this measurement from the first measurement. This number is the twist rate. For example, if the rod has 24 inches remaining at the start and 16 inches remain after making one revolution, you have 8 inches of travel, thus a 1:8 twist barrel.

 

[EGarza04]

Nice write up!

The only caveat I would add is that most monolithic bullets are longer than their weight equivalents of traditional construction, so a 55gr tsx is longer than a 55gr cup and core, bonded, FMJ,etc... so they act like heavier bullets and can sometimes be temperamental in some barrels with twist rates correct for the weight.

 

[HeadHunter]

Thank you so much for the great information!!!

 

[ZenArchery]

Good info man.

 

[Itsazonik]

that is good info to have on hand. thank you for that