# Best Round for AR-15 with 1:8 Twist



## chp.cheatham (Apr 17, 2012)

I need a little input on what grain bullet should be best for my AR-15. It has a 1:8 twist. I am using it primarily for shooting coyotes. Will a 55 grain V-Max be too light for this twist rate?


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## chuckdog (Apr 17, 2012)

It's the length, not the weight that really makes a difference in what it takes to stabilize a bullet. Some barrels with the same rate of twist behave much differently with identical rounds.

I don't recall what rates I've tried the 55 Vmax in, as I don't use them that often.

The 55 Vmax I've used in the past is a short, flat based, very lightly constructed pill, but my suspicion is they will shoot fine. I shoot 40 grain Vmax in 1/9 with very good results. Most faster rates haven't done well for me using the 40's.

Shoot them @ 50 yds, 100 yds, and 200 yds if possible. They may experience a little drift the farther downrange you get? Then again, they may be perfect?

If not, try one of the boat tail design bullets. Maybe even a 52 grain boat tail? I've not tried them, but I've heard good things about the 60 grain Nosler boat tails in faster rate rifles.

If you try them, post your results. I'd be curious to know how they do myself? Good luck, and Good Hunting! CD


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## Michael F. Gray (Apr 17, 2012)

Experiment with 5 shot groups. Every rifle is not the same.


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## SSGN_Doc (Apr 17, 2012)

My two 1:8 twist barrels work well with loads as light as 45gr and as heavy as 80 gr.  Every barrel will have a preference though.  One of these two barrels seems to do it's absolute best with a 68gr load that I use, the other does really well with a 55 gr match and 77gr match load.


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## wareagle700 (Apr 17, 2012)

55gr bulets are absolutely no problem with a 1 in 8 twist. You could even try some 40gr-45gr. The 55gr VMAX shoot great in my 16" 1 in 7.


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## chp.cheatham (Apr 19, 2012)

Thanks for the input. Hopefully, I'll get some range time soon. I'll post my results.


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## deadend (Apr 19, 2012)

75amax


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## wareagle700 (Apr 19, 2012)

deadend said:


> 75amax



Wont fit in a magazine.


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## jmoser (Apr 19, 2012)

From my RRA 1:8 24" bull upper all sub MOA at 200M:

60 Vmax max TAC
69 Sierra BTHP 23.8 TAC
75 Hornady BTHP near max Varget

Not tested in 1:8 but MOA in my 1:9 Savage:

65 Sierra GameKing 25.4 Varget

All above fit AR magazines, I use light crimp from Lee FCD.

55s at max velocity may be marginal in 1:8; muzzle velocity and twist together determine RPMs that the bullet spins at; too high can be unstable or even tear a light jacket bullet apart.

Ex:  3200 fps, 1 turn per 8 inches = 1.5 turns per 12 inches = 4800 turns per second x 60 = 288,000 RPMs ! 

As stated you have to test your loads in your rifle to be certain.  60 Vmax will buck the wind better anyway so I would go up to 60s if you like the Vmax.  I wish Hornady would make a 70-75 Vmax for .223; the 87s are incredible in my 6mm.


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## Old Texan (Apr 19, 2012)

The new May 2012 issue of Rifle Firepower magazine has an excellent article on this subject in the regular Handloading section (Page 36).

Basically it explains twist rates effects on bullets and how the Ballistic Coefficient relates to twist. The author's high recommendation is given to the Sierra Infinity software program which enables you to enter bullet weight, caliber, length, and muzzle velocity to match the ideal twist rate to the bullet.


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## riskyb (Apr 20, 2012)

My 1:8 loves 62-68gr but will shoot others with no apparent problems


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## northgeorgiasportsman (Apr 20, 2012)

As stated above, mileage may vary from gun to gun.

But my 1:8 twist Wilson barrel shot 3" groups with 55gr V-max at 100yds.
I switched to a 69gr BTHP and the groups shrank to less than an inch, which I'm perfectly fine with.


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## markland (Apr 23, 2012)

My 1-8 18in Wilson barrel on my RRA will not shoot 62gr Fed FMJ at all, but shoots incredible groups with Fed 55gr FMJ, Speer 64gr Gold Dot SP and Hornady 55gr HP and 75gr BTHP loads.
The 55gr HP Hornady is 100yds, the other 2 groups are at 200yds and it was a little windy and I think I could do a little better, but the Jard 3# adjustable single stage trigger helps some as well.  I don't have a pic of the Speer 64gr group but it was about 3/4in at 100yds. 
PS those are 1in squares on the target, don't know why they posted up so big?


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## wareagle700 (Apr 23, 2012)

Looks like it shoots real good. With those 55gr and 62gr FMJ/BT, dont expect any kind of fantastic accuracy. Its possible to stick 3 or so close here and there but groups tend to open up drastically the more shots you put in to the group. The bullets just are not consistent enough to give match quality results. But with the right ammo, that rifle looks like it will shoot!


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