Barrel twist rate

[kmon]

[Klem]

219,

I don't think you can go wrong with either twist but if pressed I think 1:8 is a good all rounder for an average length Grendel barrel.

I shoot a range of bullets from 90 to 130gn out of a couple of 6.5 calibres using 1:8 twist barrels - No twist issues that I am aware of.

I'd be using the online bullet stability calculators to confirm it is stable all the way to the subsonic barrier. The deal being that although it will be stable at the muzzle, as the intended bullet slows down this is when groups start to blow out. Don't spin it too fast that it resists pointing to the ground after the culminating point, but don't have it wobbling around too slow either.

[Dt219]

[Dt219]

[VASCAR2]

Thanks for the update. I suspect the accuracy and velocity will improve a little after the first couple hundred rounds. Lilja barrels have been getting positive feed back on this forum for several years.

[biodsl]

Swapped to the 90gr tnt...

These bullets seem to shoot well for most. Congratulations on your barrel.

[mafbloggerdanny]

dumb question incoming -- help me out guys.

I see a few of you talking about twist rate in relation to barrel length - ie 24 inch barrel with 1:9 twist vs 13 inch barrel with 1:7.5
Can you illuminate for me what relationship there is between the twist rate and the barrel length? I always thought the barrel length had more to do with velocity and the twist rate was kinda related to the length and grain of the projectiles. For example 1:7.5 for heavier bullets vs 1:9 for lighter bullets. Can you help me understand why the length should matter?

For what it's worth, I am just wondering because I'm starting to reload for my guns and I have a 6.5 Creedmoor (22") and two 6.5 Grendels (both 20") and all have 3 have 1:8 twist. So far I have only tried 129 gn flat base but I have 130 gn BTHP and 85 gn flat base waiting in the wings to test with.

[Fess]

It is related to the muzzle velocity. The goal is to get a high enough spin rate in revolutions per min to stabilize the bullet. With a given twist-per-inch barrel, the slower a bullet leaves the barrel, the slower it is spinning. To make up for the lower muzzle velocity caused by a short barrel, its twist rate must be increased.

[Mad Charlie]

dumb question incoming -- help me out guys.

I see a few of you talking about twist rate in relation to barrel length - ie 24 inch barrel with 1:9 twist vs 13 inch barrel with 1:7.5
Can you illuminate for me what relationship there is between the twist rate and the barrel length? I always thought the barrel length had more to do with velocity and the twist rate was kinda related to the length and grain of the projectiles. For example 1:7.5 for heavier bullets vs 1:9 for lighter bullets. Can you help me understand why the length should matter?

For what it's worth, I am just wondering because I'm starting to reload for my guns and I have a 6.5 Creedmoor (22") and two 6.5 Grendels (both 20") and all have 3 have 1:8 twist. So far I have only tried 129 gn flat base but I have 130 gn BTHP and 85 gn flat base waiting in the wings to test with.

You are correct.

[A5BLASTER]

dumb question incoming -- help me out guys.

I see a few of you talking about twist rate in relation to barrel length - ie 24 inch barrel with 1:9 twist vs 13 inch barrel with 1:7.5
Can you illuminate for me what relationship there is between the twist rate and the barrel length? I always thought the barrel length had more to do with velocity and the twist rate was kinda related to the length and grain of the projectiles. For example 1:7.5 for heavier bullets vs 1:9 for lighter bullets. Can you help me understand why the length should matter?

For what it's worth, I am just wondering because I'm starting to reload for my guns and I have a 6.5 Creedmoor (22") and two 6.5 Grendels (both 20") and all have 3 have 1:8 twist. So far I have only tried 129 gn flat base but I have 130 gn BTHP and 85 gn flat base waiting in the wings to test with.

I have never used a 9 twist 6.5mm barrel. Slowest I have used is 8 twist, my cz527 has a 25.5 inch barrel. It's a tack driving machine (long as I'm doing my part) all my short barrels have 7.5 twist now.

For me it comes down too wanting more twist so I can use whatever bullet I want and increase spin at maximum range to help stablize the bullet as it moves back three the transonic zone.

When my cz's barrel is finished, it will be replaced with a true 26 inch 7.5 twist 5r barrel.

The grendel doesnt produce the speeds that creedmoor,6.5x47,260 mag, so more twist allows me to use bullets that wouldnt stablize due to speed in barrels that have say a 9 twist and allows shorter barrels too use those same bullets as well.