Rifling...1-8 VS 1-9 twists

canislatrans54

canislatrans54

New member
OK, I readily admit that I'm not a "gun guy"...meaning, that I know what I know, but there are a LOT of things that I don't know.
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So, here's my question:

In the AR-15 platform, with a 16" barrel...what are the advantages/disadvantages...between a 1-8 twist, and a 1-9 twist?
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Or does it really matter?
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I would say the 1-8 would be best for 55 ish bullets in a shorter barrel like a 16 incher. The short barrel will give less velocity and less bullet rpm for a given twist rate. The faster twist will help spin and stabilize the bullet to over come the lack of velocity that a long barrel will produce.
 
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I am sure there are some guys on here that can give you more detailed info than me regarding bullet stabilization but IMO if you are looking to shoot 55 grain ammo or lighter use a 9 twist and 55 grain or higher go with the 8 twist.

From my very limited experience the 50 to 60 grain range seems to be the general rollover point for barrel twist rate choice and every barrel is different so either twist rate might shoot well in that middle range.
 
If you plan to shoot heavy bullets the 8t will be better than the 9t. If only shooting lite bullets it won't matter.
 
Assuming 223/5.56 is what we're talking about:

1/9 is the old rate with lighter bullets in mind (55 gr and under).

1/7 is a fast rate that's used for heavy bullets, it tends to be too fast for light ones. 60 gr and heavier.

1/8 turns out to generally be a good compromise that can stabilize bullets weights from lighter to heavier, I tend to think of it as a more "universal" use rate.

My Colt NM Target is a 1/7. it loves 68 gr Hornady BTHP's, but generally not 55 gr factory loads. I have found that I can load 55 gr BT's for it if I back the powder charge off & slow them down a bit, otherwise they over stabilize & the groups open up.
 
Yes, that's what I get for assuming. The question is about .223/5.56.

I just had noticed that some of the guns I have been looking at, are 1 in 8, and some are 1 in 9.


Probably 90% of the bullets I would be shooting, would be 55gr SP rounds, as well as a few 60gr SP...all from Black Hills. (These are what I have hundreds of.)

However, there might be some "experimenting" with the following offerings from Hornady:

...35gr NXT Superfomance
...40gr V-Max
...50gr GMX Full Boar
...53gr V-Max Superformance
 
53gr V-Max Superformance factory load shoots as well in my colt as my 68gr handloads do.

the 53gr V-Max bullet is a bit different design, it actually behaves more like a heavier bullet in regards to twist rate. but in hand loading for that rifle I still found I had to back the loads off a bit to get the best accuracy, at least with the powders I tried.

I read something about that bullet, I don't recall now if it's the ogive profile or what, but it's not the same as other bullets in that weight range.
 
I shoot up to 55's in my .22-250 @ 1/14 twist.
55'in my .223 1/12 twist. They are the same bullet at different speeds.
Now with the faster twist in .223 I have found the 1/8 to be less finicky than a 1/9 for lighter bullets which meet most of my needs.
50 grainers have grouped very well with my .223 1/8 bolt rifle and AR.
 
I agree.. Most of my rifles are 7 or 8 twist. The ones i shoot the most are 8 twist. 20" ARP 8 twist shoots 40gr Vmax and Nosler up to 80gr Bergers great.
One of my 16" is a 7 twist 5.56 chamber and its one i got lucky with. 50gr Nosler BT, 53gr Vmax, 75gr TMK all shoot under an inch at 200 yards. I use it for my daytime rifle on the farm.

IF i had to choose one twist, it would be 1:8. Its the most versatile.

But if your only goin to shoot lightweights, go 1:9 and be done.
 
For what it's worth, my Remington with a 20" barrel is a 1 in 9 and seems to shoot 60 grainers as well as 55s. I think you'd be fine with a 9 if staying under 60.
 
Originally Posted By: MPFD
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My 1:8 223 loves 40gr Vmax, 40gr NBT, 45gr TSX, etc. Also shoots 35gr and 40gr NBTLF moa.

My 1:9 223 loves 35gr up to 69gr. Haven't tried anything heavier.
 
That's good to know. I'm about to get my first 1:7 twist and I'm not really into heavy bullets. I hope it will shoot 55 decent.
 
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