22 Creedmoor twist rate

[jfjohn77]

Well... all I can say is that my Smith is shooting a 22 Creedmoor Improved (40 deg shoulder) with 6.5 tw, and he has no issues 80 gr and up.

 

[B23]

What brand of bullets and at what velocities are you fellows experiencing your bullets coming apart? In checking the Berger Twist Rate Stability Calculator, I don't find any issues even going down to their 80gr with a 6.5 tw at 3525 fps.

That would be a bullet RPM of over 390,000 and that is a lot. Maybe and that would be a big maybe they'll survive the trip on a fresh throat but I'd be very surprised a conventional lead core bullet would survive that kind of RPM once the throat got a little wear on it.

I'm launching 80gr ELD-M's at 3650 with an 8tw 22-243 Improved that puts me at a much less 328,500 RPM and they're making the trip, at least for now they are, but as my barrel gets some wear on the throat that could all change.

I talked to Sierra about those 95gr SMK's and even bought a box when they first came out. The guys I talked to at Sierra told me they weren't really designed for the hot rod 22 cal cartridges because at the higher velocities those cartridges would be capable of added to the very fast twist that was required to stabilize them to get the full BC they didn't think they'd hold together. We talked about using a slower twist to get the bullet RPM down but that would be at the expense of a lowered BC which is kind of the whole point of shooting those 95's.

 

[Thegman]

That would be a bullet RPM of over 390,000 and that is a lot. Maybe and that would be a big maybe they'll survive the trip on a fresh throat but I'd be very surprised a conventional lead core bullet would survive that kind of RPM once the throat got a little wear on it.

I'm launching 80gr ELD-M's at 3650 with an 8tw 22-243 Improved that puts me at a much less 328,500 RPM and they're making the trip, at least for now they are, but as my barrel gets some wear on the throat that could all change.

I talked to Sierra about those 95gr SMK's and even bought a box when they first came out. The guys I talked to at Sierra told me they weren't really designed for the hot rod 22 cal cartridges because at the higher velocities those cartridges would be capable of added to the very fast twist that was required to stabilize them to get the full BC they didn't think they'd hold together. We talked about using a slower twist to get the bullet RPM down but that would be at the expense of a lowered BC which is kind of the whole point of shooting those 95's.

It doesn't make sense, to me anyway, why a high velocity cartridge with slower twist barrel would affect the bullet's BC any differently than a lower velocity cartridge with a faster twist barrel. The bullets RPM leaving the barrel is factor of those two variables.

I would think that a bullet with X RPM would have the same stability and BC regardless of the barrel it came from, unless the velocity itself is the factor...???

 

[jfjohn77]

FYI....
This is where all this becomes confusing and contradictive. I have an article published on loaddata.com dated Sep 13 2022, that gives his recorded load data with velocities from a 1:7 twist bbl using 5 different bullets and 9 different loads per bullet. I used a Bullet Spin Rate Calculator for fastest velocity of each bullet and found the rates between 332229 rpm for the 90 gr Berger and 371931 for the 69 gr RMR. Now he published group sizes for each load, so the bullets obviously made it to the target, and now I'm left scratching my head. I think with my 6.5 twist, as long as I keep my RPMs down below those I calculated from that article, I wouldn't have a problem. Of course the barrel would be different and I would have to find an accurate load in there somewhere below those listed velocities, but that is what I enjoy and why I handload.

.22 Creedmoor Loads Using Peterson Cartridge Small Rifle Primer Brass | Load Data Article​

The .22 Creedmoor is nothing more than the 6.5mm or 6mm Creedmoor necked down to accept .224 bullets without any further changes (necks may require turning or reaming to ensure proper chamber fit/bullet release). The trim-to length is 1.91 inches, like the 6mm Creedmoor. The .22 Creedmoor makes...
loaddata.com

Bullet Spin Rate Calculator - Calculator Academy​

Bullet Spin Rate Calculator Basic Calculator Advanced Calculator Enter any 2 values to calculate the missing variable Muzzle Velocity (fps) Barrel Twist
calculator.academy

 

[Formidilosus]

FYI....
This is where all this becomes confusing and contradictive. I have an article published on loaddata.com dated Sep 13 2022, that gives his recorded load data with velocities from a 1:7 twist bbl using 5 different bullets and 9 different loads per bullet. I used a Bullet Spin Rate Calculator for fastest velocity of each bullet and found the rates between 332229 rpm for the 90 gr Berger and 371931 for the 69 gr RMR (SMK). Now he published group sizes for each load, so the bullets obviously made it to the target, and now I'm left scratching my head. I think with my 6.5 twist, as long as I keep my RPMs down below those I calculated from that article, I wouldn't have a problem. Of course the barrel would be different and I would have to find an accurate load in there somewhere below those listed velocities, but that is what I enjoy and why I handload.

.22 Creedmoor Loads Using Peterson Cartridge Small Rifle Primer Brass | Load Data Article​

The .22 Creedmoor is nothing more than the 6.5mm or 6mm Creedmoor necked down to accept .224 bullets without any further changes (necks may require turning or reaming to ensure proper chamber fit/bullet release). The trim-to length is 1.91 inches, like the 6mm Creedmoor. The .22 Creedmoor makes...
loaddata.com

Bullet Spin Rate Calculator - Calculator Academy​

Bullet Spin Rate Calculator Basic Calculator Advanced Calculator Enter any 2 values to calculate the missing variable Muzzle Velocity (fps) Barrel Twist
calculator.academy

It is an approximation, not a hard line.

 

[wind gypsy]

As others have said, not an exact science. Longer barrel, tighter bore diameter (0.218"), rougher bore/throat, hotter barrel, all increase the likelihood that they go poof.

Edit: Excalibur only had 0.219 bore 6 groove options for 6.5 twist when I looked quick so that is good vs say a .218 bore 3 groove.