What barrel twist for copper?

[deckhandmike]

I’m not reloading yet and I prefer off the shelf ammo that’s usually available. 130 and 150 are on the lighter to mid end of copper for factory offerings, I’m thinking 130 for everything but elk. Copper benefits from going faster so I’m comfortable with that grain at speed for killing everything from hog to deer to elk.

And yes a reloading set up is in my future. One thing at a time.

[ar15barrels]

Twist rate depends on velocity (which depends on load and barrel length) as well as the bullet length so there's no right answer without ALL the details.

[1859sharps]

I?m not reloading yet and I prefer off the shelf ammo that?s usually available. 130 and 150 are on the lighter to mid end of copper for factory offerings, I?m thinking 130 for everything but elk. Copper benefits from going faster so I?m comfortable with that grain at speed for killing everything from hog to deer to elk.

And yes a reloading set up is in my future. One thing at a time.

Factory ammunition is manufactured to work in commonly manufactured rifles.

if there is any issues to be aware of using a specific box of ammunition such as won't work with X twist, good for only X twist or barrel length etc it should be on the box the ammunition is coming in and/or the manufacture web site where the talk about this specific load.

Barring any warnings from the manufacture, it is reasonable to expect any commercially manufactured box of ammunition will work safely and reasonably well in any rifle that is chambered for that cartridge. Maybe not optimally, but good enough and safe.

[ShaunBrady]

I'd go with at least 1:11 and probably 1:10. It'd work well with the 150ttsx as well as popular jacketed long range bullets for the 308.

Barnes recommends 1:12 minimum. Their 308 ammo gives 2900 fps from a 24" barrel. At 59 degrees and sea level, 1:12 gives a Sg of 1.26. I wouldn't go there for a new barrel. I might test those bullets if I already had a 1:12 barrel, but probably not and I wouldn't buy that barrel intending to shoot that bullet.

You might not hunt at sea level, but you might zero there. 20 degrees colder covers about 1000' higher elevation on a Density Altitude calculation. As long as we're checking twists in 1" increments, altitude isn't likely to change the outcome. I think smaller increments are making the calculation something it's not.

1:11 gives 1.54. 1.5 is the currently recommended minimum and a little more is the general practice for lower density copper solids. If the barrel is much shorter than 24", lets check 2700 fps, the Sg drops to 1.50.

1:10 gives 1.86 which is about where I start for long range jacketed bullets if I'm buying a barrel.

If the gun eventually uses jacketed bullets, 1:10 gives 1.69 with a 178 ELDx at 2700 fps, 1:11 gives 1.39. I use the 168 ELDm with a 1:12 308 to well beyond hunting ranges. I don't see an ELDx version of that weight though.

The ballistics for that Barnes load surprised me. It does pretty well trading velocity for BC when compared to the ubiquitous 175smk/Varget load.

In a hunting application, I'd think about just going with the 150 for everything. There is some value in just one set of ballistics to remember for a gun that isn't used for hundreds of rounds a year.

I used AB Analytics for the Sg calcs and BC data. Some solvers include it but may use another term for it.

[BB1776]

I’m in a similar boat, OP, except it did not occur to me to seek out this info until after I bought my 1:12 Model 70.

1:12 works for me up to 150grns of copper, heavier/longer than that and you want a faster twist, ideally. I’m clearly not at Shaun’s level but the 1:12 is what I got and I have killed pigs with it!

[LindenBruce]

Ok, while what I'm about to say doesn't pertain to .30 Caliber bullets, it does pertain to copper bullets. I was at the range last week trying to sight in some of my rim fires with all copper ammo.

On my fairly newer Ruger 10/22 with the factory barrel I was getting 2" groups with the CCI 21gr. lead free copper rounds at 50 yards. I jumped over to 100 yards to see how they would do.

At 100 yards with the same ammo I could not even hit the target!!! Judging by the impacts in the dirt around the target it was roughly a 2 foot group size!!

Well, so much for solid copper in .22LR. The box is labeled MEATEATER. More like just grab your fishing pole. B.

[deckhandmike]

Solid suggestion on just running one bullet weight. It will be a 20” barrel.

[MeatyMac]

Badlands Precision, which makes some awesomely high BC monolithic copper bullets, recommends 1:11 twist for their 150 gr. .308 dia. Bulldozer-2 bullets https://badlandsprecision.com/produc...r-bulldozer-2/

Sailor, I'm assuming that you are not running a can, why are you going w/a 20-inch barrel, to save weight, better maneuverability, maybe both?

.

If "copper doesn't mind being spun fast", that would be because it, as a homogeneous material, will be better balanced along it's axis.

Just another reason why folks who use and like pure copper projectiles really like 'em.


/cap'n obvious

Hmmm, "homogeneous" or "monolithic", I can't get my head around the correct terminology for solids but there seems to be quite a bit of use of both terms for what I'm seeing as the same thing. What is your thought on homogeneous?

https://en.wikipedia.org/wiki/Monolithic_bullet

.

[deckhandmike]

Not going with a can. I want a short barrel for kinda a road hunting gun. I hunt a large private property with lots of roads and terrain, most of our pig hunting is run and gun style out of the truck or sxs.

So the build will be a 20” rem 700 with a proof carbon barrel, folding chassis, detachable mags for quick loading. I like a lighter gun that fits easily in the front seat and maneuverable while climbing over fences and thick brush. I don’t really care about long range ability since it’s private property. I can generally get pretty close since the game is not pressured. Doesn’t have to be a fancy receiver since it’s a 300 yard gun that needs to shoot just average. But I like a light barrel and folding stock so most of the money is going there and glass. It’s such a nice property I do all of my CA hunting in one spot so I’m building a rifle just for it.

[ar15barrels]

Not going with a can. I want a short barrel for kinda a road hunting gun. I hunt a large private property with lots of roads and terrain, most of our pig hunting is run and gun style out of the truck or sxs.

So the build will be a 20? rem 700 with a proof carbon barrel, folding chassis, detachable mags for quick loading. I like a lighter gun that fits easily in the front seat and maneuverable while climbing over fences and thick brush. I don?t really care about long range ability since it?s private property. I can generally get pretty close since the game is not pressured. Doesn?t have to be a fancy receiver since it?s a 300 yard gun that needs to shoot just average. But I like a light barrel and folding stock so most of the money is going there and glass. It?s such a nice property I do all of my CA hunting in one spot so I?m building a rifle just for it.

Why not go with a 16"-18" barrel then?
You don't need 20" unless you are shooting to 400yds or more.
16" will do 250-300 fine.
All you need to be concerned with is that you get to 26" long while the stock is folded.
Get your chassis and work backwards to 26-1/4" overall folded length with your barrel length choice.

[MeatyMac]

Why not go with a 16"-18" barrel then?
You don't need 20" unless you are shooting to 400yds or more.
16" will do 250-300 fine.
All you need to be concerned with is that you get to 26" long while the stock is folded.
Get your chassis and work backwards to 26-1/4" overall folded length with your barrel length choice.

Maybe, his desire to use factory ammo is influencing his 20" decision. Factory hunting ammo tends to use powders that perform better in standard 22-24 inch barrels but might still perform well in a 20-inch one, when you get down to a 16" barrel in the same cartridge a faster burning powder will tend to perform better.

[deckhandmike]

I’m going with 20” to get the muzzle blast a little farther out as I don’t always have ear pro on and it will retain a bit more velocity if I need to reach out with copper. Figured it’s a nice balance between short and silly short. I did think about 18” though. I’ll be reaching out to Randall once I get the rest of the cash for the barrel together to have him mount it.

[buckwildpow]

1:10 Barnes up to 150gr TTSX 308 very accurate. With 20” Sandero
1:9 Barnes 168 Gr TTSX 308 with 22” Sandero
Verify which Proof barrel contour, length and model in the Caliber you want on their chart, 1:10 and 1:9 work well with 130gr,150gr, 168gr TTSX Cooper Bullets and Proof barrels 308.

[deckhandmike]

I’m going with the 1/10.