.44 mag twist rate & over-stabilization

[grounz]

Hey everyone, I'm posting here as a last resort as I couldn't find any definitive info, I would be grateful if someone here can set me straight.

I'm re-barreling a model 629 .44 magnum revolver and was given a Douglas blank marked as 44 mag, 1:14 twist (checked the twist myself to confirm). From what I've gathered, 1:16, 1:18, 1:18 3/4, and 1:20 are the industry standards, and I haven't found much info on this blank (Douglas doesn't even list 44 mag on their site, and I haven't had a chance to call and ask). I know Shilen has 1:16 and 1:20 blanks, but I'd prefer to use this blank as it was free.

My thought is a faster twist rate is better for heavier/longer bullets, and in my research I've tried JBM's ballistic calculator and a few others sites. My worry is that 1:14 is too fast and will over-stabilize the bullet, or perhaps if over-stabilization isn't much of an issue, then jacket separation.

Can anyone here tell me:

1. Is 1:14 too quick?

2. If it's good to go, am I restricted to heavier grain bullets?

3. Is there something else I'm not considering?

4. What .44 mag firearm uses a 1:14 twist? It seems very uncommon...

Thanks in advance guys

 

[WR Moore]

OK, I looked at the current Douglas website and while it seems they're no longer producing pistol caliber barrel blanks (.45 ACP excepted*), that might be a COVID related thing. However, they do list a barrel for the .444 Marlin, which would be the same bore & groove specs. Available twists are given as 18-22 inches per revolution, your choice.

My ancient Douglas spec sheet gives their standard .44 Mag twists are 1-14, 1-16 and 1-36. 1-20 was available as special order and I've still got a blank in that twist.

I'd kinda expect that a 1-14 twist was intended for those manly types who sneer at any bullet below 300 grains and are trying for more weight. FWIW, at one time a lot of folks in the PPC game were hot on a 1-10 twist for wadcutter loads at near air rifle velocities.

You might drop Douglas a letter/email and see what they think about the issue. It's been decades, but they did do great customer service. You will note, the 1-14 twist rate is no longer in production.

*Douglas did supply blanks for a lot of folks who made 1911 barrels. Possibly they still do.

 

[Protocall_Design]

The 1 in 14 will be great for anything from light target loads through magnums. You are not going to spin a 44 too fast when they are using 1 in 7 for 223 bullets at around 3000 fps. I rebarreled a 686 with a 1 in 10. It shoots everything from bunny fart wadcutter loads to 357 Mag in tight groups. I'm getting around 2" groups with 170 to 180 gr. JHPs at 100 yards with it.

 

[steelslaver]

To see actual rpms a bullet would turn fps X 60 for feet per minute then twist rate converted to turns per ft. 12/inches per twist to get twists per foot, then that times ft per minute. So a 44 mag at 1400fps would travel 84,000 feet in a minute and turn 84,000 rpm from a 1 in 12 twist. A 1 in 10 twist 12/10=1.2 turns per ft so it would spin at 100,800 rpm. A 1 in 14 (12/14=..857 turns per ft) 72,00 and a 1 in 16 63,000

For an idea I installed a 1 in 8 premium grade heavy barrel on a 6mm Remington. That is 1.5 twists per ft. At 3400 fps or 204,000 ft per minute, for 306,000 rpm, 75 gr HP completely lose it and if they do hit a target they probably keyhole. I believe the bullets I was using just can't take it and were Coming apart. Maybe ones with heavier jackets would work. But I also got quite a bit of copper fouling with the 75s, as is hard on a bullet to engage that rate of twist rifling while under that much acceleration A 100 boat tail at 3000fps is turning "just" 270,000 rpm and are very accurate.

My point is I do not think bullets "overstabilize". I think they either are accelerating past the ability to fully engage the rifling or spin past the point that they can maintain their structural integrity..

I doubt you can get enough velocity out of a 44 mag with a 1-10 twist to cause problems with any weight bullet. Dead soft 200 gr behind 24 gr of 2400 maybe, but jacket or hard cast not so much

 

[Protocall_Design]

What he said.^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

 

[Claymore33]

This discussion brings up another question, what is twist rate of MODEL 29-2 and Model 27-2?

 

[steelslaver]

I think around 1-in 18 was standard

But, a muzzle loader firing round balls runs about 1 in 50, around 1 in 30 for conical bullets

Bullets that are have poor sectional density (almost every conventional handgun bullet) don't need much rifling twist. I believe there are other things that effect handgun accuracy more. I have put 2 colt python barrels on S&W frames neither is on bit more accurate than any of my others

a 116 gr .429 lead ball has a sectiona density of about .09, a 200gr Speer HP has a sectional density of 1.55, a 240 gr HP is 1.86, a 265 gr flat point is 2.04 and a 300 gr slug would be about .233. All so low they don't need much twist and not enough difference from one to the other for twist rate to have any great effect from lowest to highest. IMHO

 

[Protocall_Design]

The twist rate on most models is 1 in 18-3/4. There are a few exceptions, but I don't know what they all are.

 

[WR Moore]

I put my copy of Charlie Askin's Complete Book of Pistol Shooting (?) in a safe place and haven't seen it for quite some time. It had a chart of the barrel specs for all the then current Colt and S&W products. IIRC, the S&W twist for the .44 bore was 1-20, which was why I ordered a blank in that twist.

As steelslayer notes, it's kinda doubtful if there's really all that much difference in inherent accuracy between the various rifling twists. Bullet length is generally the major issue in selecting twist rate*. The accuracy improvements from custom barrels is more likely due to more careful fitting (and optimizing barrel/cylinder specs) and added weight, with maybe a smidgen of improved bore uniformity.

* I've got a .223 with a 1-10 twist barrel. It'll shoot up to 69 gr SMKs very well. 75 gr Hornady HPBTs go through 25 yard targets sideways.

 

[4barrel]

My shooting buddy has a Freedom arms 1 in 20''-The book said my 29-2 is 1 in 20''. My SRH is 1 in 20'' and my Marlin carbine micro groove and 788 Remington bolt in 44 mag are 1 in 38''. The old Lyman reloading handbook has this info. I modified a Lee mold and removed the gas check for a 310 grain bullet that works good for a cheap heavy bullet. The bullet on the right is the finished product-before and after. This mold has two crimp grooves. I do have some 300 grain Speer jacketed but haven't used them yet but that is a reload topic. I'm thinking a 1 in 14'' would be for a
heavy bullet moving slow for bowling pins?

 

[Protocall_Design]

As a general rule of thumb, a slower moving bullet needs a tighter twist than a faster moving bullet. A slow velocity bullet out of a given twist rate will not be spinning as fast as a fast velocity bullet out of the same twist rate. A faster twist rate will make the slow bullet spin faster. There is a minimum rpm needed to keep the bullet stabilized. Once it drops below that rpm, it no longer goes in a straight line.

It may come out of the barrel below that number, or fall below that rpm between the barrel and target, or stay above that rpm to the target. Only if it stays above that rpm will it shoot straight. The minimum rpm is probably different for different bullets.