1:8 twist and light bullets

[ms6852]

A while back I had asked how light a bullet a 1:8 twist barrel would shoot a 223 accurately and I finally got a chance to experiment and answer my own question so here are the details summarized.

Firearm: Predator Pursuit Rock River Arms , 20" barrel, 2 stage trigger.
Hornady 40 gr VMAX bullet
Remington 45 gr jacketed hollow point
Federal American Eagle 50gr JHP
Temperature. 94 degrees
Wind 7 to 9 mph swirling

Well I must say that I was very surprised that at 100 yds the best group was achieved with the 40 gr Hornady V max bullet. The 5 shot group measured 1.5 inches with 4 shots touching and one flyer. The 2nd best 5 shot group measured 1.93 inches with the 50 gr Federal American Eagle, and the worst was the Remington 45 gr JHP which measured 2.41. Once again this were at one hundred yards.

I was shooting on a bench using a bipod . At 200 yds the wind played havoc having to adjust from 8 inches to 18" for windage. I finally was able to get good 5 shot groups but the best one came out to be Hornady again giving me 3.78 inch 5 shot group at 200 yds. American Eagle came in second at 3.91 inches, and Remington was pretty bad at 4.87 inches.

I never expected the 40 grain to do so well in a 1:8 twist now I'm thinking of reloading and performing a ladder test and this time using a sandbag to stabilize myself for more consistent shooting.

 

[kraigwy]

Light bullets work well with faster twist. Its the other way around that sucks.

This is assuming the bullets aren't thin jacketed like the older Hornet bullets.

Give you an example, the Army uses a "Mann Device to test their ammo. In the case of the 5.56, its a Remington action with a short 1:7, heavy match barrel.

They special load ammo to test the match. I have a report that the most accurate they came up with was 52 gr Match Bullets, in Remington Cases pushed by 25 grs. of 3031. Apparently Lake City was having problems with the accuracy of the ammo they were producing. The army wouldn't accept it. LC blamed the Mann. The army tested the ammo in other devices and had the same problems. Then the tested the Mann they had issued to Lake City with the above ammo and found it would shot groups of .23 MOA at 100 yards, Well with in the Army Specs.

Further investigation showed the seating dies weren't seating properly. The Point I'm making, the lighter 52 grn bullet shot quite well in the 1:7 mann,

I bought a 5.56 Mann from the CMP, and it is great for testing ammo. I used the above load and found it to be as accurate as any I have ever used.

I use the Mann to test all my 223 ammo, for two of my 1:7 ARs. a 1:12 AR and 1:12 Remington Bolt Gun (I used when I worked as a LE Sniper)

My Mann

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As further evidence the Army MTU included this bit on the subject in FM 3-22-9.

 

[s3779m]

I have a tikka lite 1/8 twist that loves winchester white box varmint loads 45 gr. only shot those when I had nothing else and was really surprised. Shoots 1/2" groups on a good and not so good day. I have the same rifle on order that you mention, have you tried any 5.56?

 

[ms6852]

I learn something every day especially when it comes to shooting. Now I have a mission to buy a Mann device. Great info thanks a lot.

 

[Hunter Customs]

I have two AR's both have 1in8 twist barrels.
The lightest bullets I've shot in them is Black Hills 52gr match load, both rifles shoot that load extremely well.
Both rifles also shoot PMC Bronze 55gr FMJ extremely well to the same point of impact as the 52gr match load.
I have not tried anything heavier or lighter then the two loads mentioned, have not found a need to.

Best Regards
Bob Hunter

 

[98 220 swift]

I have a 24" 1-8" twist wilson bull barrel on one of my ars. It shoots the 40gr vmaxs the best out of all the bullets I have tried(36gr-75gr) at 100 yards. 1/2" 5 shot groups the norm. Now at 250 yards they start loosing to the heavier bullets.

 

[rickyrick]

I have found light vmax bullets to be surprisingly accurate out of 1/7, 1/8 and 1/9.
I don't reload, but factory hornaday ammo works well within my needs. If I did reload I'm sure I could find the true sweet spot.

I used 35gr varmint grenade type bullets for fun... It's fun to vaporize liquid filled targets with them.

 

[armoredman]

I must have gotten my info backwards - I was told I needed 62 grain or higher to use my 1-7 twist 5.56mm barrel to it's fullest...so now I should look into buying some 52 grain stuff at the store? I did find two 60 grain loads that work well for a fat old man shooting un-magnified, front rest only.





Then again, I've been out of the .223 game for several years, for all I know those might be evidence of absolutely horrible shooting.

 

[Mobuck]

The AR I carry and shoot most is 1-8 and it works fine with 50-55 grain bullets of various designs.Son uses Fed 50 grain JHP for coyote shooting in his 1-8 16" AR and it does a wee bit better than the other types tried-3/4" +/- @ 100 yards.
I haven't seen accuracy of 40 grainers to be quite as good in 1-8/1-9 as I get from my bolt action 1-12 but not a good comparison due to wide variance in rifle types, trigger pull, sand bag stability, and such.

 

[armoredman]

What's his coyote load, if you don't mind me asking?

 

[Mobuck]

"What's his coyote load, if you don't mind me asking?"

Directed to my post? If so, Federal Am Eagle 50 JHP. I bought several cases of this from another dealer a decade back and it just happened to be a winner in his 16" AR.