Barrel twist
- Thread starter FNWhelen
- Start date
Guy Miner
Master Loader
- Apr 6, 2006
- 18,246
- 8,422
Choose the barrel twist for your intended bullet.
Most of the bullet makers are good about specifying which twist their long range bullets require.
Most of the bullet makers are good about specifying which twist their long range bullets require.
xphunter
Handloader
- Sep 15, 2005
- 1,714
- 3,527
What Guy said.
If you have a different range of bullets you want to use or try, get the twist rate for the longest/highest BC one you intend to use.
The one that requires the fastest twist.
If you have a different range of bullets you want to use or try, get the twist rate for the longest/highest BC one you intend to use.
The one that requires the fastest twist.
Last edited:
Idaho53
Zephaniah 3:17
- Feb 5, 2023
- 183
- 539
I have seen bullets come apart from over rotation due to incorrect twist/bullet combo. I had a good conversation with Hornady, and the formula they use for match grade type bullets is to keep bullet revolutionary under 300,000 RPM's, using the following calculator: RPM calculator is Velocity x 720 and then divide by twist rate
Examples:
3,000 FPS x 720 / 7.5 = 288,000 RPM
3,000 FPS x 720 / 7 = 308,571 RPM
Examples:
3,000 FPS x 720 / 7.5 = 288,000 RPM
3,000 FPS x 720 / 7 = 308,571 RPM
- Thread starter
- #5
I have 40 year old custom rifles that have too slow of twist for some modern bullets. But who knew back then we would have todays bullets. So if building a new gun should a guy try to get close to 300,000? If 300,000 is the high side what is a good number for too slow?
I generally don’t worry about too much twist myself. Most good bullets won’t come unglued that I’ve seen under normal use. I think the RPM problem could come under match or competition with extended shooting heat. Don’t know. But I’ve got a 7 twist 7mm barrel coming to make a 7x57 and a 7 twist 224 barrel for a 22 CM. I’m not expecting any issues. I know the extra RPMs don’t hurt bullet performance on animals.
Idaho53
Zephaniah 3:17
- Feb 5, 2023
- 183
- 539
You are asking good questions. To help decide which direction you want to go, it's really good to know how use plan to use the rifle. Will it be primarily a hunting rifle with the occasional long range precision shooting, or will it be a precision build dedicated to shooting match style. Personally, I like to decide then that then build it. Also, the rifling style and the amount of grooves makes a big difference on bullet jacket deformation, which definitely affects bullet flight (especially at long ranges). If you have an "R" type rifling, then bullet jacket deformation can be reduced. Currently, all I use is Shilen's match grade barrels with their "ratchet" rifling, they are fantastic. Have built over 15 rifles for customers with these barrels: 22 CM, 6CM, 25CM, 7PRC, 300 PRC, etc.
I like to shoot bonded bullets for hunting and match bullets for long range shooting. I have had bonded bullets spin apart mid flight due to over rotation, and I have also had bullets tumble at long range due to under rotation. Typically, there is wide margin for caliber/twist for proper bullets stabilization, but shooting high B.C. bullets need the correct formula to maximize the performance of the bullet/caliber. Solids (or Partitions) are much different than high B.C. bonded or match bullets. Hope this helps some...
- Thread starter
- #8
What got me to thinking about twist rates is I have a 22-250 and a 25-06 that both had standard twist for the time built but are too slow for some of the newer bullets. I am very pleased to see some high BC stuff coming out for a 25-06 but I don't think I can make use of them. Both of these are pretty much range toys. At this point in life any hunting I do is with a 35 Whelen or larger. Some good info here and plenty to think about before getting another rifle or having something rebarreled.
Idaho53
Zephaniah 3:17
- Feb 5, 2023
- 183
- 539
Agree with you, and I am also excited about the quarter bore bullets coming out. Just finished a 25 CM with 128 ELD-X bullets. Shoots great with high BC value. Using Shilen ratchet with 1:7 twist on a 24” tube proven to be very good at long range.
7t in the 25creed with 128 and up will work just fine in a 24" as speeds most likely won't reach 3,110. that's near 320k rpm.
here's an average per twist for 320k rpm
7 @ 3,110
7.5 @ 3,330
8 @ 3,550
8.5 @ 3,770
9 @ 4k
bullet construction is the only thing that'll determine whether it'll stay together or not @ +/- 200fps. i believe thin skinned/plated bullets will have more of the issue from the rifling than rpm's.
7 @ 3,110
7.5 @ 3,330
8 @ 3,550
8.5 @ 3,770
9 @ 4k
bullet construction is the only thing that'll determine whether it'll stay together or not @ +/- 200fps. i believe thin skinned/plated bullets will have more of the issue from the rifling than rpm's.
wvbuckbuster
Handloader
- Nov 5, 2015
- 3,375
- 3,871
I agree with Scotty as not worrying about over twist within reason. Example, first two 6brs I had were 1-12 or 14 twist. Couldn't use any bullet weight over 75 grs. Then went with a 1-8 twist and had some of the Sierra 70gr MKs left as I had moved on to 105-108gr bullets. Offered to a friend who said that they wouldn't shoot in HIS 1-8 twist because it was too fast. So, I loaded some up put 4 shots in one hole and showed him. He bought my 70gr bullets
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