Can somebody please explain the difference...

From my under standing the 1/9 twist is good for the lighter bullet weights. So 55grain to 62 grain would probably be optimal bullet weight for that twist rate. The SW Sport is 1/9 twist not 1/7. I have read of guys using 1/9 twist up to 69 grain and the gun still being accurate(not personally though). 1/7 twist will obviously shoot the lighter bullets, just not as accurately as that twist rate is used to stabilize the heavier bullets.. The ruger with 1/8 twist seems to be a good compromise for the range of bullets you stated you wanted to shoot. PSA does make some 1/8 twist barrels. Go with 1/7 if you wanted to shoot the higher grain bullets more imo. I am sure someone more knowledgeable can give you some better info, but i think for the bullet weights you want to shoot 1/9 or 1/8 would work best.

Everready is pretty much spot-on. Faster twists for heavier bullets. 1:8 is a good middle ground for commercial ammo, if the rest of the rifle is set up the way you want, but the others should be fine, also. Pmags are pretty much mil-spec, the most reliable in my experience, all I use now.

1:9 - most commercial ARs until recently. Works fine with bullets up to 68-69gr BTHP. Some people report good results with Hornady 75gr as well, but this twist is too slow for Sierra 77gr or anything longer/heavier. If you want to use bullets lighter than 55gr, this is the best choice of these three.

1:8 - ideal for typical AR shooting, plenty of stability for up to 77gr but not excessive like 1:7

1:7 - the military twist rate since the M16A2 debuted in the 1980's. Stabilizes extremely long bullets in bitter cold temperatures. Faster than needed if you aren't shooting M856 tracers in the arctic.

If you aren't going to use bullets heavier than 69gr, all three work fine. If you want to use light fast varmint bullets, 1:9 or slower is a better choice. If you want to use 77gr SMK or similar, you'll want 1:8 or 1:7.

1 in 8 seems to be the sweet spot for being able to handle a wider variety of different bullet weights.
This last weekend I made some 75 grain BTHP's and my 1 in 8 barrel handled them very well. When I finished testing them I went to some 69 grain BTHP's and they were again very accurate. I finished by plinking some 62 grain commercial stuff, again, very consistent.
I think 1 in 8 is as close to all purpose in the AR as you can get.

The main question is: Will it make a hill of beans' difference, with the 50-65gr. ammo most of us probably will use?

Click to expand...

Short answer, NO!

But I prefer to err on the side of a faster twist. A 7 twist is more likely to shoot somewhat lighter bullets better than a 9 twist will shoot heavy bullets. Most bolt guns and early AR's by the way have 1:12 twist for really light bullets. Even a 9 twist is faster than the round was originally intended for.

There's a huge amount of misinformation in this thread. Fast twist rates allow you to stabilize long/heavy bullets. They do NOT cause problems with light bullets. The idea that slow twists are optimal for light bullets is a myth.

Depends on use. Self Defense Carbine I've got 1:7 & 1:8 and will generally shoot 55gr out of them. Highpower AR has a 1:9 for heavier rounds out to 600 yards using Black Hill rounds in the 62-77gr range.

The 3 twist rates you mentioned won't make a hill of beans difference, your bullet weight, intended target, range, optics and overall amount of practice/range time will make the most difference.

The mags... both work fine. When the D&H GI style mags are on sale for $7 or less at PSA I grab those. Buddies lend me PMAGs etc and they also work just fine. I personally don't like the look of them but they are good mags and would work just fine.

Consider chamber as well as twist rate when comparing the three.

Generally speaking, the 1:8 twist barrels may also include a "Wylde" chamber. Which is considered to be the most "accurate" of the three. ymmv

http://www.americanweaponscomponents.com/products/clearing-the-caliber-confusion-223-wylde-vs-5-56-nato/

I'm with Taliv. A 7 twist gets the job done with virtually every bullet commonly available for .223. The .223 doesn't have the horsepower to spin apart light weight bullets, and even 40gr bullets still work fine in a 7 twist. The bigger issue is how the chamber is setup. Some real accuracy and precision gains can be had from setting up a chamber correctly for the intended bullet. There's no use having .120 freebore if you're going to be shooting 40's and 50's where a zero freebore will work.

1:7 was put into service for stabilizing tracer rounds. Everyone wants what the military has so therefore it became popular.
I have advocated for the 1:8 as the perfect twist for years. The 1:9 or 1:8 will serve you well. More and more barrel manufacturers are offering the 1:8 these days because people are waking up to it.
My most accurate AR is a 1:8 with 69 grain ammo.
My go to gun is a 1:7 and shoots what ever I run through it. It's a 1:7 because it's all I could get when I built it.
My other rifles are 1:9. If I ever build another or replace a barrel it will be a 1:8.

1:9 is probably the most versatile, will stabilize everything from 40 to 62 grain.

1:8 is your best choice is shooting a regular diet of bullets heavier than 60gr.

1:7 was adopted simply to stabilize the longer tracer round. If you're not shooting tracers (which are unusually long for caliber and weight due to construction), it will be of no use. Although, some have reported good accuracy with bullets as light as 55gr with it. I do have a 1:7 barrel and my experience has been acceptable with M193 but not stellar.

I prefer 1:7 so I can shoot long 70gr solid copper hunting bullets but the vast majority of what I shoot is 55gr M193.
As far as magazines, all you mention are fine. For new aluminum buy D&H or Okay. Pmags are fine too.

The idea that slow twists are optimal for light bullets is a myth.

Click to expand...

Ever try sending a round ball down a fast twist barrel?

The reason the .454 uses a slower twist than .44Mag or .45Colt is because it reduces pressure. There are plenty of reasons and circumstances where a faster than optimal twist is undesirable.

Llama Bob said:

There's a huge amount of misinformation in this thread. Fast twist rates allow you to stabilize long/heavy bullets. They do NOT cause problems with light bullets. The idea that slow twists are optimal for light bullets is a myth.

Click to expand...

Yes and no. The faster you spin the bullet, the more the slightest imbalance in the bullet is magnified, which affects accuracy. Serious benchrest shooters will go to great lengths to find the slowest twist that will still stabliize the bullet.

Spinning a bullet faster than necessary can amplify any inconsistency in the bullet. Since we use J4 jackets, you can shoot Berger Bullets in faster twist than what is listed. We list the slowest twist rate needed because we want to squeeze every bit of accuracy out of a rifle.

http://www.bergerbullets.com/wp_super_faq/why-do-you-recommend-the-slowest-twist/

Click to expand...

That said, for practical purposes with a sporter weight rifle if you're shooting 55-65 grain bullets I wouldn't worry whether a 1:8 was too fast and I certainly wouldn't go to any special effort to get a 1:7.

natman said:

Yes and no. The faster you spin the bullet, the more the slightest imbalance in the bullet is magnified, which affects accuracy. Serious benchrest shooters will go to great lengths to find the slowest twist that will still stabliize the bullet.

Click to expand...

Benchrest shooting is subject to all sorts of pixie dust worship. Most of it, when put to the empirical test, is worthless. That's the whole point of what Litz (and several others) did.

Remember too that OP is writing about and AR and "minute of coyote" accuracy. The accuracy problems inherent in an auto action are MUCH more debilitating to gnats ass accuracy than any issue involving twist rate. For that sort of application, on a new gun just buy a 1:7 twist barrel, and know you won't have any problems with any normal bullets at any air temperature/pressure combination.

Llama Bob said:

Benchrest shooting is subject to all sorts of pixie dust worship. Most of it, when put to the empirical test, is worthless. That's the whole point of what Litz (and several others) did.

Click to expand...

Just because the effect of a given factor is so small that it's only of interest to benchresters (where even the tiniest advantage is important) doesn't mean it's "pixie dust worship".

Llama Bob said:

Remember too that OP is writing about and AR and "minute of coyote" accuracy. The accuracy problems inherent in an auto action are MUCH more debilitating to gnats ass accuracy than any issue involving twist rate. For that sort of application, on a new gun just buy a 1:7 twist barrel, and know you won't have any problems with any normal bullets at any air temperature/pressure combination.

Click to expand...

I agree, which is why I said it wasn't worth worrying about in a sporter weight rifle.