Twist rate copper bullets

[Captain1018]

I have read about twist rate and bullet length, are the considerations different for copper bullets as compared to lead?

Does copper bullet need the same twist as the same length lead bullet (with the copper bullet being lighter for the equivalent length)? Or does bullet mass (grains) dictate the twist rate?

 

[180ls1]

It *needs* to be faster because its less dense which lowers stability.

 

[Article 4]

It *needs* to be faster because its less dense which lowers stability.

True - it also is very different due to CoG versus CoP which affects all bullets but more so with all copper due to the distribution of weight

 

[Macintosh]

You can plug your info into the berger or another stability calculator and see fairly easily. My impression is a lot of people get ok performance from bullets that compute to “marginal” stability, but it’ll get you in the ballpark.

 

[JFK]

The considerations aren’t really different. It’s just that a bullet will be longer for a given weight, so you’ll bump up against instability faster if using cooper AND you are trying to load the sleekest, highest BC copper bullets. The vast majority of copper bullets were designed to work with the traditional twist rate of a given cartridge. If you are starting from scratch and rebarelling a traditional 1:10 cartridge maybe go to a slightly faster twist. The newer stuff..creedmoors, prc’s etc, are all fast enough for it not to be an issue worth thinking about.

 

[Captain1018]

Tikka seems to be dragging their feet updating the 300 WSM, still 11:1.

 

[Captain1018]

If I go 300 WM (kinda leaning that way) Barnes has 165 gr and 180 gr loaded copper. I assume elk won’t care either size, is there a consideration other than accuracy to go bigger or smaller?

 

[pods8 (Rugged Stitching)]

If I go 300 WM (kinda leaning that way) Barnes has 165 gr and 180 gr loaded copper. I assume elk won’t care either size, is there a consideration other than accuracy to go bigger or smaller?

Velocity at impact at your desired distance is your main consideration with selecting a mono (obviously it needs to be stable and accurate too. Personally that’s 2200+fps for me and most Barnes to get good expansion, not “minimum expansion”.

 

[Captain1018]

So if I’m looking for 500 yards barns ttsx

165 has 2114 fps and 1638 ft lb
180 has 2063 fps and 1702 ft lb

The 165 has the *better* 500 yard performance because it will expand and mushroom better? Is 2200 fps a specification they state? I haven’t come across that.

 

[JFK]

So if I’m looking for 500 yards barns ttsx

165 has 2114 fps and 1638 ft lb
180 has 2063 fps and 1702 ft lb

The 165 has the *better* 500 yard performance because it will expand and mushroom better? Is 2200 fps a specification they state? I haven’t come across that.

168gr is the one that opens up at lower velocity in 30cal versus the 165. Ft/lbs is not what you should be concerned with. Velocity on impact is what’s important. Speed will open them up, create the larger frontal diameter, and creates a better wound channel. 2200fps is a safe, somewhat conservative, velocity for getting good performance out of monos. It’s not an absolute, you can go below it, but it’s a good place to operate in for predictable results.

 

[Koda_]

I have read about twist rate and bullet length, are the considerations different for copper bullets as compared to lead?

Generally you will need a faster twist rate for a copper bullet of the same weight as a lead bullet.

Does copper bullet need the same twist as the same length lead bullet (with the copper bullet being lighter for the equivalent length)? Or does bullet mass (grains) dictate the twist rate?

I don't know if its mass or length or a combination of both that determines twist rate but generally if the two bullets are the same length the twist rate would work just the copper bullet of the same length will be a bit lighter.

 

[pods8 (Rugged Stitching)]

Is 2200 fps a specification they state? I haven’t come across that.

No, they state lower numbers which some folks cling to (not saying you do) and don't get the performance they want and others like me who uses barnes alot will comment to stay at a higher velocity and then the person will say "but Barnes said I only need 1800fps" and then turn around and complain about how it performed terminally. Their minimum expansion velocity gets you minimum expansion, IE the petals peel back just a little bit (plenty of photos on the internet), when you hit faster the petals peel back further and create a larger diameter.

Some of the LRX bullets have lower minimum velocities (1600fps and 1400fps in some cases) which I might consider creeping down a bit below 2200fps for my uses but again I'm not going anywhere near those minimum numbers.

 

[pods8 (Rugged Stitching)]

Here is an example of velocity differences, mind you each bullet design they have is a little different but as noted if you're 2200+fps you're typically into more consistently performing territory.

 

[180ls1]

Tikka seems to be dragging their feet updating the 300 WSM, still 11:1.

Look at browning. My 6.5 prc and 300 prc are both 1" faster than saami.

 

[BCsteve]

Tikka seems to be dragging their feet updating the 300 WSM, still 11:1.

The new ones are 1:10.

 

[rickyw]

Barnes .308 caliber 168ttsx opens 1.7x @ 1500fps and it is recommend to stay 1-200 fps above that to get 2x expansion. When in doubt shoot the shoulder
You can always email Barnes customer service for minimum expansion velocity of a particular bullet. They should reply