Best 5.56 ammo for a 1:9 twist

Lots of good defensive loads work well in that twist rate. Basically anything under 70 grains should be fine. Are you wanting a fragmenting round or a more solidly built "barrier blind" round?

I have a stainless 1:9" PSA upper that shoots the ADI 69gr Sierra SMK ammo into tiny groups.

I couldn't ask for better performance at $12.99/20 round box. Cabelas stocks it.

There is no way to answer your question. You need to try different brands until you find what is most accurate in your rifle. As previously stated, keep bullet weight under 70 grains.

The general rule for 1:9 is 69 gr. suggested max but it really is not a hard and fast rule. Rifle barrels are a bit strange in that some will shoot differently than others despite having the same specifications. Some may do fine at 70 or even 75 gr. Often it is more problematic to try to shoot varmint type very light bullets in a fast twist as the bullets can literally come apart in flight. Bullets that are heavy for a twist rate can fail to stabilize which obviously affects accuracy.

As long as the throat of your barrel and magazine allows it (assuming an AR--bolt actions are a bit different), you can try heavier bullets and most likely they will be less accurate than a lighter one but then again, they might not. It might also make a difference if you have a .223 chamber, a .223 wylde chamber, or a 5.56x45 chamber as the throat on these varies which can have an affect on accuracy on its own depending on how far you seat the rounds.

http://www.gunsandammo.com/ammo/pair-barrel-twist-rates-ammo/

"...that will be a stopper..." Nothing will give you a 100% guaranteed one shot stop on anything. Even a rampaging ground hog. No such thing as "Defense" out to 300 yards either.
However, Stag Arms suggests 45 to 75 grain bullets for a 1 in 9 twist. If you're not reloading, you'll have to try a box of as many brands in that range of bullet weights as you can to find the ammo your rifle shoots best. The price of said ammo means nothing. I'd be thinking SP's.

What I've found, after building and rebuilding hundreds of AR's in the last couple decades, if you can't get 27.3grn Varget under a 50grn V-max to shoot well in a 1:9" to 1:6.5", something is wrong with your rifle.

The 50 Vmax is a violently expanding bullet design, and in the absence of barriers and armour, will produce very quick kills on game, and I'd expect the same performance on human recipients.

The best news about the 50 v-max, there are a bunch of factory ammo options which use this bullet. The Remington 50grn Accu-tip is the same 50grn V-max, just with a green tip, then other loaders like HSM load the 50 vmax as well. For the reloader, they're super cheap.

My end of times and all-around choice is the readily available 55gr soft point. The V-Max is extremely accurate but for regular plinking 50-62gr SPs are close enough.

I also love the 69 gr SMK in my 1:9, 16" Delton.

some folks say that 1:9 can't stabilize a 69 gr. bullet, but mine does it just fine, every time.

I must end up with all the weird or mis-marked barrels. I keep reading that I need less than 70 grains (or whatever) for a 1:9, but my 3 1:9 AR's built with DPMS 16" barrels and my Mossberg MVP Thunder Ranch keep shooting 77 grain MK 262 and Hornady 75 grain BTHP match in MOA or better groups. As did my rifle with a 20" 1:9 ER Shaw barrel.

you just need to try different ammo your rifle will tell you what it prefers,

For me I find 855 and 193 good for plinking or bulk stash type ammo and I also find them dirty and not very accurate, compared to my hand loads both 855 and 193 is sad in the accuracy and cleaness department, really depends on what you want and find acceptable,

55 VMAX for me.

I would see how 55 grain FMJ works. If you're happy with the accuracy results, then that's going to be your most economical option, and it generally has very good terminal performance.

Redfisher60 said:

What about M855?

Click to expand...

Of everything I used in the military (and elsewhere) M855 was the most inconsistent, excluding garbage from russia.

I've had good experiences with M855. Decent penetration and good terminal ballistics. That being said it is an inconsistent round because of its construction. I don't buy it ever as I find M193 to be cheaper and better for everything I do. M193 is also more consistent in terminal ballistics but even then isn't great. While I keep M193 as my stockpile, I keep a few mags of real defensive loads for home defense.

My department uses Federal 55 grain TRU ammo which uses the 55 grain Sierra Game King bullet. It has very good terminal ballistics as long as you don't need to shoot through a barrier. Also very accurate load in our old 1in9 Bushmasters and our current 1in7 Colts. It does have penetration on the lower side so keep that in mind if needing to shoot at an awkward angle.

If you want barrier penetration or just a round with more penetration I'd go with a good bonded soft point or a full copper bullet. The Speer Gold Dot 62 grain is a good barrier blind round with lots of real world use. The Federal Fusion 64 grain hunting round uses the same bullet. The military adopted the 70 grain TSX as a specialty bullet and reportedly that's what they used to turn Bin Ladens head into a canoe. If you're barrel doesn't stabilize the 70 grain TSX (its long for its weight) the 55 grain version is also supposed to work well. Just be aware that the TSX and similar all metal bullets have a lot of penetration.

The long heavy target type rounds like the 77 grain M262 and the 75 grain TAP are known to yaw and fragment pretty reliably. I can personally attest to the terminal ballistics of both of those rounds being very effective. However general rule of thumb is a 1in9 barrel won't stabilize these rounds at distance. However that's not a concrete rule and you'd have to test it to be sure.

62g Federal Fusion. Relatively easy to find online and on store shelves. Good performance, not unreasonably expensive.

Redfisher60 wrote:
For a 1:9 twist barrel. The ammo is for defense and accuracy up to 300 yards.

Click to expand...

If you don't reload, try something like these: https://www.midsouthshooterssupply....5-grain-v-shok-nosler-ballistic-tip-20-rounds

If you reload, I have had very good luck with Hornady 60 grain Spire Point (both soft and hollow) bullets riding on top of an appropriate powder (IMR-4198, IMR-3031, IMR-4064 and Winchester 748).