SmallCaliberCentral

What rate of twist are most of your ar's? My stag has a 1/8 and I read its for 70-80 grain bullets. Would it still stabilize a 55 grain?

I have the DPMS Panther Bull Twenty-Four and it is a 1:9 twist. I am no expert in ballistics but I'm sure there will be some from this site that are and will answer that with facts. The heaviest I have shot out of mine is 50 gr and it loves them.

Twist is MOSTLY used as an arguing tool for folks on boards.
YES, it will stabilize a 55gr bullet, or anything light. Here is the rub with twist rates.

Military uses a 7-twist,(actually I think it is 7.75) MOST commonly found is a 9-twist.
Twist rates can vary by 1/2 twist(from stated) quite frequently regardless of maker.
9-twist will stabilize(bullet LENGTH dependant, and twist variance) MOST 70gr, and some heavier.
The SMK 70gr was in fact designed for the 9-twist barrels.

Now what people forget, or don't know; is that twist... NOT velocity, kills bullets.
Hornady(spoke with them just yesterday) has a RPM limit on their SP, AND Vmax bullets of 290,000 RPM.

The formula is: MV * 720 / Twist = RPM.
So if you wanted to shoot a 40gr Vmax from YOUR barrel: 290,000 * 8 / 720 = 3,222 FPS
3200 fps is the max velocity for your gun with 40gr. Not very fast at all. MOST of the cheap bullets(SXSP, Dogtowns, etc) have thin jackets, and are limited to around 240,000 RPM.

So if you use a faster twist barrel, you may have to limit yourself to heavy bullets, or slower velocities.

Happy shooting!

Darkker wrote:Twist is MOSTLY used as an arguing tool for folks on boards.
YES, it will stabilize a 55gr bullet, or anything light. Here is the rub with twist rates.

Military uses a 7-twist,(actually I think it is 7.75) MOST commonly found is a 9-twist.
Twist rates can vary by 1/2 twist(from stated) quite frequently regardless of maker.
9-twist will stabilize(bullet LENGTH dependant, and twist variance) MOST 70gr, and some heavier.
The SMK 70gr was in fact designed for the 9-twist barrels.

Now what people forget, or don't know; is that twist... NOT velocity, kills bullets.
Hornady(spoke with them just yesterday) has a RPM limit on their SP, AND Vmax bullets of 290,000 RPM.

The formula is: MV * 720 / Twist = RPM.
So if you wanted to shoot a 40gr Vmax from YOUR barrel: 290,000 * 8 / 720 = 3,222 FPS
3200 fps is the max velocity for your gun with 40gr. Not very fast at all. MOST of the cheap bullets(SXSP, Dogtowns, etc) have thin jackets, and are limited to around 240,000 RPM.

So if you use a faster twist barrel, you may have to limit yourself to heavy bullets, or slower velocities.

Happy shooting!

Ill just have to stay at the 3100-3200 fps area when I do my loads then. Thanks Darkker.

If I did my math correctly 55 grain v-max at 3200 fps is 288,000 rpms.

Savageboy,

I talked to Hornady a day or two ago, here is what they said about the 55gr Sp's AND VMax's.
Barrel smoothness dependant, of course. 290,000 RPM ceiling.
IF you need more headroom for spin, 55gr BlitzKings have a ceiling of 352,000 RPM; according to Sierra.

Sorry to burst bubbles but I just shot a bunch of V-max 40 grain .223's which I chrono'd at 3400 fps with no stabilization problems. I shot squirrels to about 250 yards with 'em. They group .41" @100 yards at the range. I have a Stag Arms 24" BBL 1:8 twist. Blows the squirrels sky high, BTW. This velocity was not even max powder load. I had max powder showing 3700 fps, but they heated up the barrel too much and were less accurate.

Glad to hear it. 8-twist @ 3400 = 306,000 RPM; which is 5% different.
I don't recall saying that the world would end, merely passed on the "stated" RPM limit for a 55gr bullet, not 40gr. As with all things barrel smoothness is a big part of that.

I had max powder showing 3700 fps, but they heated up the barrel too much and were less accurate.

... If you are running that much velocity out of an 8 twist barrel, I'm surprised that the bullets even held together....I went to a custom 1/14 barrel to push 40gr rounds at that speed and higher...

I was pretty suprised that my 40 grainers held together too, but they did! I've shot Nosler varmageddon, vmax, and sierra blitzkings in 40 grains and all shoot well with my Stag.

As a note on RPM, I have many common 22-cal varmint bullets RPM's, from the manufacturers, listed over on shootersforum.

I have a Rock River NM with a 1 in 8 barrel and a Colt Match Target with a 1 in 7. They both shoot Hornady v-max 55 grain bullets very good. I'm shooting just under 25 grains of H4895.