1:7, 1:8, 1:9 twist?

[Rastoff]

These three twist rates are quite common. They seem pretty close together though. Is one particularly better than another?

My .308 is 1:10 and that seems pretty common for that caliber. So, why the smattering of twist rates for .223Rem/5.56mm?

 

[JaPes]

These three twist rates are quite common. They seem pretty close together though. Is one particularly better than another?

My .308 is 1:10 and that seems pretty common for that caliber. So, why the smattering of twist rates for .223Rem/5.56mm?

It's because of the range of projectile weights available for .223 Remington. I believe the range goes from as low as 30 grains to a high of 90 grains.

How to Pair Barrel Twist Rates with Bullets | Guns & Ammo

^ Maybe this will help?

 

[OKFC05]

Yep, long bullets need more twist to stabilize, and the .308 typically sticks to bullets that don't require the faster twist.

Overstabilized can be overdone too, (over is better than under) so the mighty "combat .22" has different barrels for different purposes.

 

[Waywatcher]

Rastoff, you sure do like those rabbit holes!

1:7 or 1:8 will give the most options when selecting ammo. 1:7 still launches 55 grain FMJ just fine but can also launch 77 OTMs. 1:8 is good too. 1:9 is pointless--if you want to be able to shoot the heavy bullets you will need a faster twist or if you want to shoot only lighter bullets get a slower twist like 1:12. 1:12 launches the 55 grain FMJ just fine too.

 

[cyphertext]

Waywatcher beat me to it... I was going to point out that you forgot about the 1:12.

 

[Arik]

I wouldn't say 1/9 is pointless. 1/7 is certainly more versatile but 1/9 is not pointless. They launch heavy bullets just fine. I've owned both and can't really see much difference. 1/7 is more accurate further out with heavier loads but the difference is small.

Sent from my SCH-I545 using Tapatalk

 

[SiGfever]

For the average shooter feeding 55grn bullets 1:9 works well. If I had to choose I would get a 1:8 or 1:7 to have a do-it-all rifling. YMMV

 

[Waywatcher]

There's not a good do-it-all rifling; a choice has to be made:

Is the rifle going to be used with:
A.) "Varmint" bullets weighing 35-55 grains? Or,
B.) "Military-style" bullets weighing 55-77 grains?

If the answer is:
A.) 1:12 is the best bet.
B.) 1:7 or 1:8 is the best bet.

1:9 is a poor compromise that cannot shoot either the lightest weight varmint bullets nor heavyweight OTM bullets very well.

 

[JaPes]

Waywatcher beat me to it... I was going to point out that you forgot about the 1:12.

Don't forget the 1:14

 

[Rastoff]

Waywatcher beat me to it... I was going to point out that you forgot about the 1:12.

I didn't forget about it, I didn't even know it existed before the article JaPes linked.

The rounds that are most commonly available to me are the 55gr or 62gr. I posted the question because those three are what I see most often for .223 barrels.

So, if faster is better for heavier bullets, why does my .308 have a 1:10 twist when the lightest rounds I've found for it are 147gr, almost three times heavier than the 55gr .223 rounds?

 

[Waywatcher]

Length. Bullet length that is. There is also a bullet characteristic that takes into account the ratio between bullet diameter and weight, called sectional density. Some more easy reading for you to do!

It's the reason that 70 grain Barnes TSX .224 bullets need a 1:8 or faster twist to stabilize--they're solid copper thus longer than a jacketed lead bullet. Weight is a more common and easier dimension to talk about than bullet length, though.

 

[Rastoff]

Length. Bullet length that is.

Now I feel stupid. Yes, that obviously makes sense. Thanks for that info.

See, the learning continues even though I'm often denser than lead. Have we found the bottom of this rabbit hole?

 

[JaPes]

Do you reload/handload ammo? You might want to look into it. It's the rabbit hole to the right.

 

[vipermd]

Alice called: 308 cal are available in weights of 110-230 gr, and rifle (308) twist rates may be 1:10,11.25,12,12.5. Obviously the BC's are all over the place with that range of bullets. Some good for varmints, deer/bear, SD, target, long range target, subsonic/supersonic. So 223 cal has a range of 60 gr from top to bottom, while 308 has a range of 120 gr from heaviest to lightest. Speaking of density you could range from copper- brass-bronze- osmium, pick your use, range, twist and they will determine your BC/weight {mass}. But I must go, I'm late, very,very late!!

 

[Maddmax]

It's because of the range of projectile weights available for .223 Remington. I believe the range goes from as low as 30 grains to a high of 90 grains.

How to Pair Barrel Twist Rates with Bullets | Guns & Ammo

^ Maybe this will help?

Hmmm. Now I understand (even better), why my 1-10 twist Mini 14 shoots so good. The twist is perfect for 52-53 grain BTHP bullets screaming out the barrel at 3300 f.p.s. The 55 grain BTFMJ would hold their own too if I backed them off a few grains, but anything heavier than 55 never worked out that well. It hated 60 grain and up. Anything under 50 grain or soft points I'd smoke the bullet out the end of the barrel...

 

[Maddmax]

Alice called: 308 cal are available in weights of 110-230 gr, and rifle (308) twist rates may be 1:10,11.25,12,12.5. But I must go, I'm late, very,very late!!

And there are different grooves too. 4 groove 6 groove....

 

[Rastoff]

Do you reload/handload ammo? You might want to look into it. It's the rabbit hole to the right.

Yes, but very limited right now. I'm only doing .45ACP and 12ga at the moment. I will add a couple more handgun loads before I jump down the rifle reloading hole.

 

[JaPes]

Just buy a set of .223 dies already, you know you're going to do it anyways. Then you'll need some case lube, a case length gauge and trimmer, primer pocket reamer or swager to get rid of military crimps, a keg of CFE 223... you know, all the necessary rabbit hole supplies.

 

[Rastoff]

Just buy a set of .223 dies already, you know you're going to do it anyways. Then you'll need some case lube, a case length gauge and trimmer, primer pocket reamer or swager to get rid of military crimps, a keg of CFE 223... you know, all the necessary rabbit hole supplies.

You are an evil, evil man!

When I do start down the rifle path (which is probably too complicated for a simpleton like me) I'm starting with .308Win. As long as I can get .223Rem for $400/1,000 I'll be happy with my 2MOA accuracy. The .308 is a tad more expensive and I want to reach out further with it so, accuracy is more important.

 

[JaPes]

.308 Win is even more fun. So far I only load for a bolt gun, so no full length resizing. Just neck sizing. Out of the different calibers, I find two to be troublesome. The tapered 9mm cases combined with hard cast lead projectiles are a pain. Reloading .357 Magnum gives me the heebie jeebies.