1:9 twist

[USMCM16A2]

Gents,


Is the 1:9 twist adequate to handle a 75 grain Hornady A-Max ?. For bolt rifle use ?. In .223 Thanks, USMCM16A2

[NRAhighpowershooter]

1-9 is kinda pushing it..... I wouldn't go heavier than 69gr my self with that twist....

[buffybuster]

Whether the bullet will stabilize is based on it's length relative to it's diameter rather than it's weight. If you have the bullet and a good dial caliper (or equivalent) you can use the Greenhill Formula to get a good estimate on the recommended twist rate.

The 1/9 barrels will generally stabilize bullets up to about 69grs with few issues. With that said, every barrel is a little different. So to address your original question; questions you should ask yourself: what are your accuracy expectations?, to what range are you going to shoot?

Regarding stated twist rates; all manufacturers have some variance in their actual versus stated twists. A barrel might be marked 1/9 but it might actually be 1/8.75 or 1/9.25. Barrels rifled using the carbide button or hammer forging process typically show some slight variance in twist rates.

The only way to find out, it to shoot it and see......... but my best WAG is that the A-Max is a long bullet for caliber and as such would probably not meet my accuracy expectations. Probably a 1/8 twist would be best for the 75gr A-Max.

[rksimple]

I've used the 75 gr Amax in my Savage 12fv with excellent results. Its a stock 1 in 9 barrel. I keep them around 2850 or so and they stabilize fine. I've gone out to 800 yards with that combo so far.

Try them and see. As was said, every barrel is different. You may luck out.

[Prc329]

YMMV but I used 75 A-Max and 77 SMKs with good results before I sold the gun (Savage 10fp). The barrel was stock 1-9 with a brake that was cut to 20". The bullets stabilized fine. The 69g SMKs were more accurate but the 77s were happier to 600 yards.

[ar15barrels]

Velocity is a factor here.
More barrel length obviously gives you more velocity.
A 16" may or may not stabilize the 75's, but 20's usually do.

[rue]

If you had a 16" barrel and a 1:9 twist what grain should you use? I hear 55 grain is no go.

[ar15barrels]

If you had a 16" barrel and a 1:9 twist what grain should you use? I hear 55 grain is no go.

huh?

55's shoot fine in 1:9 barrels no matter the length.

1:12 is optimum for 55gr bullets.
1:9 is optimum for 69gr bullets.

[uscbigdawg]

I think if I was building a 223 bolt gun (or using 223 bullets), I'd go for a 1:7 or 1:8 and run some crankin' loads with 77's and 80gr. VLD's.

Rich

[6079Winston]

The most accurate load I have found for my 20" 1-9 Bushmaster uses 75 gr Hornady HPBT and Reloader 15. I haven't tried the 75 gr AMAX, but I think the Hornady service rifle data used a 1-9 Citadel barrel.