optimum Weight for Twist

[tufrthnails]

Is there a formula for finding the optimum Weight projectile for a twist by Cartiridge?

[LoneWolf]

Berger has a good twist calculator on their website. What are you trying to figure out?

[tufrthnails]

TY LW. What weight to start off with in my 6.5 creed 1-10 twist 24" barrel.

If 140s fly at all decent that is what I am going to hunt with, but for punching paper I want to go with the optimum weight.

Edit: Looks like the 140's and 143's should fly well. I really should have checked that before I bought a rifle, but it was an after thought. I'm glad its should work out good for me.

[Shooter0302]

It's not the weight that determines the twist needed , but the length that determines the needed twist.
http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

[Shooter0302]

Run these two bullets, Speer .224, 70 gn semi SP , length .7895 and a 69 gn SMK ,length .8940

[darkker]

Edit: Looks like the 140's and 143's should fly well. I really should have checked that before I bought a rifle, but it was an after thought. I'm glad its should work out good for me.

Ehhh..... Hows that?
The 143 ELD-X is 1.44" long, and the 140 ELD-M being 1.374"
So firing WITHIN SAAMI pressures, you are only marginally stable. This can mean terrible groups, or just lost BC.
A 10-twist in a Creedmoor is a varmint weight shooter.

[tufrthnails]

Ehhh..... Hows that?
The 143 ELD-X is 1.44" long, and the 140 ELD-M being 1.374"
So firing WITHIN SAAMI pressures, you are only marginally stable. This can mean terrible groups, or just lost BC.
A 10-twist in a Creedmoor is a varmint weight shooter.

Not according to the info I was running, but I could easily be entering it wrong. I'll have to recheck the numbers. I did some break in and at 100 yards it looks great. Won't get to stretch it out for another couple weeks.

Edit: Man I'm glad you jumped in and helped me out on that. I have no idea where I pulled my data from. I was having a hard time finding length on Hornady rounds at work, but I did end up finding some numbers. They were way wrong. Especially since they settled in at around .750" at 100 yards at end of my break in. Which seems they will be perfectly fine for normal hunting distances. I'll find out when I stretch them to 400 yards in a few weeks, but I'm gonna start working some shorter bullets for my paper punching plans. There is so much of this I don't know yet. This site is great for helping guys trying to get a little more out of their shooting/ reloading.

Side note this may become my go to for Yote hunting!

[Robinhood]

Berger's gyroscopic stability factor calculator using G7 puts your 143 at an SG of 1.0 where 1.5 is stable. A 1.12 for the 140 ELD M. Both have a suggested twist of 8. Berger is normally liberal with twist rates. Regretably I don't have any examples of the lighter bullets. Have you considered 100 grain options from Sierra and Nosler? 3000 fps sounds like a lazer.

[eddiesindian]

Berger's gyroscopic stability factor calculator using G7 puts your 143 at an SG of 1.0 where 1.5 is stable. A 1.12 for the 140 ELD M. Both have a suggested twist of 8. Berger is normally liberal with twist rates. Regretably I don't have any examples of the lighter bullets. Have you considered 100 grain options from Sierra and Nosler? 3000 fps sounds like a lazer.

Agreed. Sure liked to see what that 1-10 in 260 flys at with lighter pills.

[tufrthnails]

I'm gonna try some 100g Amax first. And see what it does. Then I may try some other brands. First I gotta find a little heavier bullet that my brother can use for deer hunting this Nov. The plan was to get it so he can hunt I got another thread with the vertical issue I seen yesterday, but another member suggested tuning the action screw. 129 definitely seem to have more potential then 143s. I'm very very curious to see what I can get with the 100s. But until I can get out past 100yards I really won't know.

[tufrthnails]

I'm gonna work some 100s over the chrony as soon as they come in. That little ragged hole is such an addictive goal!

[Robinhood]

Many a deer has fallen to a lightweight 243 bullet. The right bullet is critical in a lighter weight hunting projectile. Contact the bullet manufacturers for the correct product choice to bring down the game your after at the muzzle velocity you have.

[tufrthnails]

Yep I've killed a few with 100g .243 interlocks before I started reloading. Shot placement can be a little more critical. I like heavy bullets on deer seems to knock them on there butts, but .243 has been slaying deer long before I started hunting. It's funny to me how as soon as you get a little cocky thinking you got something figured out life kicks you in the head and reminds you how little you really know!

[Zero333]

I have not heard of anyone shooting a 10twist 6.5 creedmoor. With the odd exception, just about everyone shooting the 6.5 CM has an 8 twist barrel.

Take a nylon bore brush on a cleaning rod and run it through the barrel to figure out the real twist...

Insert brush in the barrel...
Once the brush starts to spin, stop and make a mark on the cleaning rod,
Take a tape measure and measure from the receiver (or the bore guide mouth) to the cleaning rod handle,
push the rod down the bore and stop once the mark you made makes a full revolution,
then measure from the same point to the handle.
Subtract the smaller # from the bigger and you get your true twist.

Simple and conveniently done when cleaning the barrel.

I wouldn't shoot anything heavier than 120gr in a 10 twist 6.5 Creedmoor.

[Robinhood]

Some guys are selling Wilson barrels in 6.5 Creedmore 10 twist on other forums. There is no info on this Wilson barrel manufacturer. Not Wilson combat.

[tufrthnails]

I have not heard of anyone shooting a 10twist 6.5 creedmoor. With the odd exception, just about everyone shooting the 6.5 CM has an 8 twist barrel.

Take a nylon bore brush on a cleaning rod and run it through the barrel to figure out the real twist...

Insert brush in the barrel...
Once the brush starts to spin, stop and make a mark on the cleaning rod,
Take a tape measure and measure from the receiver (or the bore guide mouth) to the cleaning rod handle,
push the rod down the bore and stop once the mark you made makes a full revolution,
then measure from the same point to the handle.
Subtract the smaller # from the bigger and you get your true twist.

Simple and conveniently done when cleaning the barrel.

I wouldn't shoot anything heavier than 120gr in a 10 twist 6.5 Creedmoor.

I'll be dam$#d they sold it incorrectly. I did six times just to be sure 1-8 Everytime. Thanks for the heads up. Love this sight so much knowledge here.

[Zero333]

So now with your 8" twist barrel you're good to go with any 6.5mm bullet weight !!!

Life can be peachy like that. :angel:

[tufrthnails]

So now with your 8" twist barrel you're good to go with any 6.5mm bullet weight !!!

Life can be peachy like that. :angel:

Sure is peachy!!!! Now to get time to hit the range and tune the action screws like I was advised to try in the other thread. I loaded a charge test with some 129s and some 140s.

[tufrthnails]

Got to the range today with a charge weight test I loaded the other night. 140g SST w/superformance powder. .5g increments. Found a nice group at 1g below max published that shot 5 rounds at .794" one stragler round the 4 in a nice ragged hole so I have promising point to start from with a powder I had no previous use for. I'll get the seating depth figured with that load then go back and do a 1g spread at .2g increments.

[darkker]

We did a pile of Pressure Trace work with Superformance powder in the Creed a few years ago now.
That is a VERY progressive burning powder, so you can be about 10-15,000 psi off SAAMI max, and you will only give up 75-100 fps with a 140gr.