Twist rate for .223 cast bullets

[MeestaSparkle]

For a 60 grain cast lead bullet, given the options of 1 in 9, 1 in 12, or 1 in 7, what would be the better option?

[felix]

12 ... felix

[Bullshop]

dito 12
BIC/BS

[Buckshot]

...............My Savage single shot, M112 in 223 has a 12" twist and shoots a 56gr just fine. Don't have a 60 though. However it will shoot the Speer 63gr SMP very accurately.

..................Buckshot

[JeffinNZ]

I have a Rem 700 ADL in 1-12 twist and it spins up a 225462 in WW at 61gr just fine.

Cast is quite a bit shorter than their jacketed cousins you see.

[Blammer]

is there a different "set of rules" when shooting cast bullets vs jacketed bullets with respect to twist rate?

I'd think any of the above listed twist rates would be good. Why is 12 better?

my experience is with mostly jacketed bullets and for that wt 1:9 and 1:7 both would be good with 1:7 being more desireable if heavier bullets were wanted.

[verney]

is there a different "set of rules" when shooting cast bullets vs jacketed bullets with respect to twist rate?

That rule has nothing to do with bullet weight. Suitable twist rate depends on bullet length and diameter.

[felix]

And weight on the circumference of the projectile. You can use hollowpointing to adjust inertia, which throws the "weight" to the rotational part of the circumference dynamically. Never use more twist than necessary to overcome the resistance presented by the ambient conditions throughout the intended trajectory, just in case your projectile is not perfect. The more perfect your projectile is, the more twist it can handle, provided the projectile is tough enough to withstand being brought up to final rotational velocity required by the ambient, and holding it enough to hit the target. ... felix

[Blammer]

verney-thanks for the reminder, I knew that specifically but didn't elaborate on the question.

felix-thanks for the details.

I suppose my real question is, why does everyone suggest a 1:12 twist when shooting jacketed 60 gr bullets 1:12 would probably be the LAST suggestion?

Do you want to barely stabilize the lead projectile vs a jacketed bullet?

Is there a down side to getting a faster twist? IF not why not get a faster twist.

[Scrounger]

verney-thanks for the reminder, I knew that specifically but didn't elaborate on the question.

felix-thanks for the details.

I suppose my real question is, why does everyone suggest a 1:12 twist when shooting jacketed 60 gr bullets 1:12 would probably be the LAST suggestion?

Do you want to barely stabilize the lead projectile vs a jacketed bullet?

Is there a down side to getting a faster twist? IF not why not get a faster twist.

Yes, too much twist will cause a bullet to self destruct a few yards out of the muzzle. I saw that many times trying to shoot Sierra 50gr Blitz bullets in an AR-15 with 7-1/2" twist. If it can blow up a jacketed (admittedly thin jacketed) bullt, it will certainly destroy lead. I've had my best .22 caliber cast accuracy with an older Remington .222 that had a 14" twist and was rechambered to .223 Rem.

[Buckshot]

...............We're not talking schuetzen here but back then, they might be driving a pre-engraved soft lead projectile to 200 yds. It was said they wanted only enough spin to make the slug stable to that range. If, after passing through the target it tumbled, who cared?

..................Buckshot

[rattletrap1970]

I have a Savage 12 BTCSS .223 with a 1 in 9 twist barrel. It absolutely hates 52-55gr bullets. It is fantastic with 69gr Sierra HPBT. Can anyone suggest a mold for a .223 that is up in the 69-77gr range?

Thanks,

Rich

[edsmith]

I have a AR that I built from a gi kit about 15 years ago , it has the triangle hand guards, 1 in 7 twist, I think, it shoots 55 gr. great , but keyholes with 62 gr. don't know what it would do with cast boolits.

[Larry Gibson]

1 in 7 twist, I think

Might want to actually measure the twist. Sounds like a 12" twist to me.

Larry Gibson

[Doc Highwall]

The fast twist barrels can be funny sometimes. My two Remington 40X rifles in 223 Remington both have 1-8" twist barrels and Remington test fired both of them at the factory with 52 grain HP bullets and both shot 3/8" or smaller five shot groups. The 1-12" twist barrels will allow you to shoot the cast bullet at a higher velocity before accuracy goes south.

[Larry Gibson]

Blammer

I suppose my real question is, why does everyone suggest a 1:12 twist when shooting jacketed 60 gr bullets 1:12 would probably be the LAST suggestion?

As mentioned it is about the length and diameter of the bullet, not about the weight. The 225462 many times weighs close to 60 gr when fully dressed. The length of 225462 is probably shorter than most jacketed SP or SP/FMJBT 60 to 64 gr bullets, hence it will stabilize in a slower twist. The Sierra 63 gr semi-pointed bullet will many times stabilize in 12" twist ARs when the muzzle velocity is up around 2900+ fps. You all are dancing around that nasty old concept most don't think applies but it does. That is RPM and the bullet must have sufficient RPM to stabilize. Given a fixed twist that means higher velocity to get the essential required RPM. With 225462 I actually get very good accuracy (the best) out of my 14" twist barrels with velocities above 1900 fps.

Do you want to barely stabilize the lead projectile vs a jacketed bullet?

That is precisely what you want to do except you really want to do it with both kinds of bullets. The less RPM the less the centrafugal force can adversely affect accuracy. That's why the schutzen shooters use the least twist for 200 yard accuracy and why the Palma shooters use the least twist for 800, 900 and 1000 yard matches. You want to use the best twist for a specific bullet in a given velocity range not a "general twist that will stabilize a large range of bullet weights. That's why/how I get very good and consistent accuracy at 2600 fps with my 14" twist .308W barrel with cast bullets It's how the cast bullet bench rest shooters get the best accuracy also.

Is there a down side to getting a faster twist? IF not why not get a faster twist

The "down side" is that the faster the twist the higher the RPM and the higher the centrafugal force. That translates into a lessor velocity range for accuracy. Wonder why 99% of all '06 cast bullet shooters shoot with velocities in the 1600 -1900 fps range? The reason is to go above that successfully with the standard '06 10" twist and shoot consistent accuracy with cast bullets takes some doing. You can push 2200 fps with a 12" twist barrel and higher yet with a 14" twist barrel. The same applies to the .223 or any other cartridge where the RPM can approach or go beyond 140,000. The best twist in the .223 for cast bullet accuracy is 12 or 14" twists. With those you can get very good accuracy upwards of 2200+ fps. That is very hard to do with a 7 or 9" twist, especially in shorter barreled ARs.

The answer to MeestaSparkle is; get the 12" twist.

Larry Gibson

[jayjay1]

Dear Gents,
excuse me please for diggin´ out this old threat, but it exactly hits what I´m looking for!

My barrel is given as I´m having only this one AR (which are not that easy to get over here).
It is a 20" long and 1:9 twist barrel.

I could have a 65 or a 75gr. cast bullet from the mold maker of my choice, which both will be powder coated and GC´ed.

Am I right, when I say, that the heavier bullet compared with slower powder would give me more opportunity to run the system reliable?
So the 75gr. bullet would be my choice.

But normally I can´t stabilize such heavy bullets in this barrels, speaking for FMJs, where the top is reached at about 69gr..
On the other hand I think, that pure lead bullets will be shorter than FMJs with the same weight.

So, which one is the way to go for me, 65 or 75?

[KrakenFan69]

Since this thread popped back to the top I happened across it. Larry I can't thank you enough for that explanation. That totally makes sense to me now. I wonder, is there some sage advice for determining max velocity of a given projectile based on it's length, shape, weight etc? I run a 1:7 AR and recently purchased the Arsenal 225-61 Elvis NLG mold. I'm hoping to try some powders like H4198 and W748 to get the thing to cycle and get "Minute Of Gopher" accuracy out to 300 yds. Having a better understanding of my target zone velocity wise would certainly help.

Thanks for all the knowledge you and all the others have shared over the years here

Kraken Fan #69

Blammer

I suppose my real question is, why does everyone suggest a 1:12 twist when shooting jacketed 60 gr bullets 1:12 would probably be the LAST suggestion?

As mentioned it is about the length and diameter of the bullet, not about the weight. The 225462 many times weighs close to 60 gr when fully dressed. The length of 225462 is probably shorter than most jacketed SP or SP/FMJBT 60 to 64 gr bullets, hence it will stabilize in a slower twist. The Sierra 63 gr semi-pointed bullet will many times stabilize in 12" twist ARs when the muzzle velocity is up around 2900+ fps. You all are dancing around that nasty old concept most don't think applies but it does. That is RPM and the bullet must have sufficient RPM to stabilize. Given a fixed twist that means higher velocity to get the essential required RPM. With 225462 I actually get very good accuracy (the best) out of my 14" twist barrels with velocities above 1900 fps.

Do you want to barely stabilize the lead projectile vs a jacketed bullet?

That is precisely what you want to do except you really want to do it with both kinds of bullets. The less RPM the less the centrafugal force can adversely affect accuracy. That's why the schutzen shooters use the least twist for 200 yard accuracy and why the Palma shooters use the least twist for 800, 900 and 1000 yard matches. You want to use the best twist for a specific bullet in a given velocity range not a "general twist that will stabilize a large range of bullet weights. That's why/how I get very good and consistent accuracy at 2600 fps with my 14" twist .308W barrel with cast bullets It's how the cast bullet bench rest shooters get the best accuracy also.

Is there a down side to getting a faster twist? IF not why not get a faster twist

The "down side" is that the faster the twist the higher the RPM and the higher the centrafugal force. That translates into a lessor velocity range for accuracy. Wonder why 99% of all '06 cast bullet shooters shoot with velocities in the 1600 -1900 fps range? The reason is to go above that successfully with the standard '06 10" twist and shoot consistent accuracy with cast bullets takes some doing. You can push 2200 fps with a 12" twist barrel and higher yet with a 14" twist barrel. The same applies to the .223 or any other cartridge where the RPM can approach or go beyond 140,000. The best twist in the .223 for cast bullet accuracy is 12 or 14" twists. With those you can get very good accuracy upwards of 2200+ fps. That is very hard to do with a 7 or 9" twist, especially in shorter barreled ARs.

The answer to MeestaSparkle is; get the 12" twist.

Larry Gibson

[Larry Gibson]

"Am I right, when I say, that the heavier bullet compared with slower powder would give me more opportunity to run the system reliable?"

You are correct.

"But normally I can´t stabilize such heavy bullets in this barrels, speaking for FMJs, where the top is reached at about 69gr..
On the other hand I think, that pure lead bullets will be shorter than FMJs with the same weight."

Yes, most cast bullets are shorter than their equal weight jacketed counterpart. A 12" twist will stabilize a .652" long bullet down to 1200 fps.

Larry Gibson

[cpy911]

Larry,
Would a projectile from a 1:8 twist, 10.5" barrel at about 1900-2000 FPS stabilize?
Projectile is RCBS 22-055 55 grain semi point.