1/7 twist AR...what have you found to work the best ammo wise?

It should shoot 55 - 60 grain Ballistic-Tip or Hollow-Point varmint loads quite well.
Look for Hornady V-Max or Nosler Ballistic-Tip.

FMJ military bullets of any weight are the lowest quality and least accurate bullets made.

Any bullet type with the jacket opening in the nose (B-T, SP, HP) will be more accurate then ones with the jacket opening in the base (FMJ, FMJ-BT).

I believe the bullet type will make more difference then the weight of the bullet.

rc

1-7 stabilizes 62 grain well. Its all I shoot out of my A2 , shes an MOA gun sometimes, but usually 1.5 to 2 and I can live with that.
55 grain is better stabilized in a slower twist barrel, 1-9 and so on

Mine with a 20", 1-7 twist, Service Rifle profile barrel, not a Service Rifle match rifle though, shoots about everything from 55 grains to 80 grains. I have not tried anything heavier or lighter.

.7" to .8" MOA at 100 yards with 55 grain Hornady V-max or Sierra Blitzkings

55 grain is better stabilized in a slower twist barrel, 1-9 and so on

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Then why for some of the 1/7 AR tests I see have smaller group averages with 36 grain varmint grenades and 50 Grain V-Max then 55 or 62 FMJ bullets??

55 grain bullets will shoot just perfectly fine in a 1/7, if the bullets are any good.

rc

I thought the only problem with shooting light for twist bullets was over spinning them causing them to fall apart. Not a real problem I hear about with modern bullets. I agree with RC the issue is not very accurate bullets, or not very accurate barrel.

FMJ military bullets of any weight are the lowest quality and least accurate bullets made.

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Really?

I've seen much worse quality ammo than Lake City M193 or M855.

Yes really!

Do some accuracy testing of Lake City M193 or M855 as opposed to a good varmint load and you will believe it.

I am not talking about quality of the loaded round.
I am talking about bullet weight variation, unlevel bullet bases, and off-center balance of the projectiles themselves.

rc

Stalker, do NOT let yourself get all wrapped up in the "twist." Twist aside, AR barrels are just like any other rifle barrel. Each will show a preference for different types of ammunition.

Although 1:7 is a pretty fast twist, the only thing I'd avoid is going with anything super light, like the 30 something grain bullets or the thin skinned 40 something grain bullets. I've had more than one 1:7 twist barrel that preferred 52gr HPs to 77gr HPs to about 300 yards or so, at which point the higher BCs of the heavier bullets came into play.

If you are basing your opinion of 55gr bullets on shooting you have done with military/surplus ammo, I'd suggest that you try some better bullets. Although M193 is pretty popular and is usually reliable, I've found it to be some of the most inaccurate stuff out there. The 55gr FMJ projectiles that they use plain suck.

In any case, what kind of AR is it? Is it a target model or a field rifle? You may be banging your head against the wall for nothing. Don't chase groups if you don't need it to shoot good groups. Most ARs shooting almost any sort of ammo will shoot straight enough to hit a clay pigeon at 100 yards.

If you just want to see what your rifle will do, I'd suggest getting some 69 gr Sierra Match Kings and load them up with some Reloader 15. That should give you a good idea of what your rifle can do. If the utmost in accuracy is what you're after, try the Sierra 52gr HPs for the closer in stuff.

24grains of Re15 underneath any match bullet 68grains or heavier should do very well for accuracy in a 1:7 twist.

I'd also give 60gr flat based varmit bullets a nod for short range accuracy out of that twist.

Jimro

I've only shot 55gr M193 through mine so far.
1.7 MOA average.

Good enough for government work.

A 1/7 twist is designed around 62 gr or heavier. Some guns, with some ammo will shoot 55 gr OK but I've never seen any that would shoot it as well as heavier bullets. My only 1/7 gun would shoot it acceptably, around 2"-2.5" or so at 100 yards, but 62 gr or heavier would pretty consistently shoot closer to 1".

Unless I'm mistaken, the 1:7 twist came about to stabilize the long tracer rounds that the military was using. It has nothing to do with the bullet weight. Heck, I've seen 1:12 twist barrels do just fine with 62gr projectiles with the more common profiles.

Most accurate bullets I've used in the 223/5.56 is the Sierra 52gr match...

Ok, so I have a new AR

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C'mon man, tell us more. You know we always like to see pics of new guns too...

I would think a 1-7 would shoot the light bullets just fine. Now I believe alot of folks here have touched on different aspects and all added together they pretty much have the answer.
Now not knowing what your ammo and the make of your barrel is I will take it is a standard 1-7 twist chrome lined quality barrel and not one of the cheap one's out of those kits that are floating around (seen some very bad ones). Plus I take it for granted you are not twisting the barrel by putting sling pressure on a pencil thin barrel and your barrel nut is tight.

If you wish to see how your ammo is go ahead and mic them for the od of the bullet. Remember if you are shooting massed produced military type ammunition the bullets are coming out of many different dies which as long as they are in tollorance are good to go. You may be surprized out of a single box how many different dia bullets you may have. Now combine that with a looser tollorance barrel and throat it can make for some wild accuracy.

If you have a very good barrel you may shoot alot of different ammo's with good results and it works the other way around if you have very good ammo you may get away with shooting not so good of barrel.

I have seen 62gr green tip shoot knots out of a match barrel at 50 to 100 yards and know a few military match shooters use it for practice that way.

A good example of this goes the same for the m1 garand. If you have a little worn military barrel and use military ammo you may be lucky to hold minute of target.
Now that is why alot of folks in many circles use what they call mexican match.

You take a military round and remove the bullet and just drop in a quality bullet and off to a match you go. It will make a poor shooting dencent barrel into a nice tack driver. The same goes for buying a match barrel and shooting military rounds as that will work a little better also and it works with the ar15 also.

Technically it's not the weight of the bullet, it's the length. Heavier bullets are longer. The 1/7 is recommended for the heavier bullets. This doesn't mean it won't shoot everything you put through it but the military went with it for the heavier bullet.

I've been having great results with 69 grain Sierras and 68 grain Hornady match bullets. That's out of a 20-inch barrel.

I've got a 1:7 DD M4 with 16" bbl factory setup. So far still looking for best round but groups just inside 1 MOA with handloads. Nothing lighter than 55 grn Hornady FMJBT and most are 60 grn VMax or Sierra HP. Have some 73 grn Amax but have not gotten acceptable results from them so far (limited load data for that round.)

Rub is I have a Savage 1:9 M25 varmint rifle (24" bbl!) and it can do a .25" group with a 60 grn VMax, half inch or less with others except have not shot the 73 grn yet. My black rifle cannot hold a candle to that.

Not real happy with MOA results but I'll take them. Expect better but so it goes. I think the key is what you intend to do with it really and for a battle rifle MOA may do the trick (or three gun or tactical.) If you are shooting P-dogs at 250 yds maybe not so much, but they make uppers for that and that may be an option.

Thems my results so far just sayin.

Mike

My Colt 6920 seems to shoot point of aim with 55 grain FMJ rounds but shoots high using M855 green tip rounds. I've only shot out to 50 yards using iron sights with it. I may have to try 100 yards and see what happens.

Amazingly, both of my 1/7 rifles love 62gr Tula and 55gr PMC too.

BSW

in my experience the faster the twist the heavier the bullet..with my 1:8 it shouts 55-69g very well..my brother 1:7 shoots 69 the best over 55 and 62..every gun is different doesnt matter if it was made the same..we use 69g sierras the most...out of 20 3 shot groups the smallest was.221 the larges .79..the average .48..thats with a 20 inch match grade heavy barrel off a bench rest

Sadly I've only shot my 1:7 AR at 50 yards from a bench. I was shooting M855 which is 62 grain and the groups were around 1/2" to 1". I was sighting in my EoTech and BUIS and I'm not a great rifle shot.