GREENHILL, STABILITY, TWIST AND 227-80 IMPROVED

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Last Post 14 June 2016

CBA Member

joeb33050 posted this 23 May 2016

I tried 227-80, a .917” long bullet, in a Striker with measured carefully 12” twist barrel. It didn't stabilize, wouldn't stay on the paper at 100 yards.

OU812 wrote, here, of an improved NOE 227-80, .82” long without gas check, that stabilized in a 12” twist barrel.

I FILED 227-80 BULLETS TO .82” LONG, FIRED THEM IN THE STRIKER, WITH 6/TITEGROUP AND THEY WENT THROUGH THE PAPER AT 50 YARDS, SIDEWAYS.

OU812 SENT me some gas checked and lubed bullets that are .89” long and weigh 76.5 grains.

The Greenhill Formula (my weight est) says: A .224” DIA. BULLET .89” LONG MINIMUM TWIST IS 8.5”, EST. BULLET WEIGHT IS 82.3 GR. A .224” DIA. BULLET AND 12” TWIST BARREL WILL STABILIZE A BULLET .627” LONG, EST BULLET WEIGHT IS 58 GR. Today I shot 5 into .75” at 50 yards, there is no visible tipping.

This bullet shouldn't be anything like stable, based on the constant of 150 and assuming s.g. is something like 10.9. Note that the Greenhill cite, I'll put it up, says that the constant of 150 can be replaced with 200, and the bullet is stable. (bottom of first page.) The Greenhill formula with constant of 195, .224” and .89” as above, has a minimum twist of 11” per revolution. Greenhill remains correct.

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32 Comments

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45 2.1 posted this 14 June 2016

Ken Campbell Iowa wrote: besides ....it still appears that john a. has the only accurate cast bullet 223 rig in the world ....;. let us lower the bar to 2 moa groups ... anyone... ??

ken

speaking of 223 cartridges, has anyone achieved 1.5 moa ... or 2 moa.... from a 300 blackout cast rifle ?? this is getting kinda spooky ...

There are a lot of quite accurate 223 and other twenty two caliber rifles out there. They can shoot the same quality groups as other calibers do. The whole thing is “WHAT YOU FEED THEM".

As far as the 300 Blackout, I've seen two (the only ones in my experience) who reliably shoot 1 to 1.5 MOA groups with cast in semi autos....... some of which are ten shot ones. Again, it depends on what you feed them.

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Standard Member

Hamish posted this 13 June 2016

OU812 wrote: Poor ethics and marksmanship maybe?

You are shooting a 22-250 correct? Try 8.5 grains of Titegroup. If that does not work throw away that ugly Savage and buy a Remington. From the OP: "OU812 wrote, here, of an improved NOE 227-80, .82” long without gas check, that stabilized in a 12” twist barrel." It would seem you've pretty well proven that your barrel is a 14", ( which should alleviate a little of your frustration to start with.) and now you know for a certainty that your bullet will need a little bit harder kick in the behind. Will be interesting to see f you can get it to speed before the need for a GC. asserts itself.

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OU812 posted this 12 June 2016

That's a nice looking pistol. Writing is too small to read, are they single shot pistols?

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joeb33050 posted this 12 June 2016

As previously reported in these pages, the 227-80 Improved stabilizes in my 22-250 barrels with 12” twist. With only a few sample bullets to try, the bullet did NOT stabilize in the Savage Striker 22-250. The Striker has a 14” long barrel, and measuring twist is a problem-at least for me. I asked if anyone KNEW the Striker twist, and, as usual, got a buncha opinions. One man sent a page from his Savage manual. The 22-250 Striker twist seems to be 14". This explains why the 227-80 Improved doesn't stabilize. It MAY give a hint about the very nice accuracy of the Striker with cast bullets. Maybe twist is more important than we thought, in accuracy. Slower twist = smaller groups? 223 Rem 9” twist = big cb groups? Gpidaho chronographed some loads, the 7/Titegroup = ~ 1600 fps.

joe b.

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Standard Member

OU812 posted this 04 June 2016

Poor ethics and marksmanship maybe?

You are shooting a 22-250 correct? Try 8.5 grains of Titegroup. If that does not work throw away that ugly Savage and buy a Remington.

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joeb33050 posted this 04 June 2016

The 227-80 Improved did NOT stabilize at 100 yards with 7/Titegroup; in the Striker pistol. 5 shot, none hit the paper. I have no idea why.

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gpidaho posted this 29 May 2016

Hello Joe, tried to send this in a PM but couldn't get it sent. Said it didn't recognize user name. I would think you would be recognized here. lol Anyway, I haven't forgotten our project. I have the Blue Dot and TiteGroup loads ready for next range trip and though the local gun store was out of IMR4227 a shooting friend is bringing me a pound mid-week and we'll be good to go. Remembering those that served today. Gp

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CBA Member

mtngun posted this 29 May 2016

Thanks for the link, Frank. :)

The Geoffrey-Kolbe stability calculator appears to be based on Robert McCoy's “McGyro” program, as is the JBM stability calculator. After trying both, I prefer the G-K calculator simply because the input page is more user-friendly.

But when I tried plugging OU812's bullet into either JBM's or G-K's calculator -- and merely guessing at some of the dimensions -- they said it was unstable.

Miller came up with his formula in an attempt to be more accurate than Greenhill while at the same time being much easier to calculate than McCoy. http://www.jbmballistics.com/ballistics/bibliography/articles/miller_stability_1.pdf>Technical explanation here.

Miller's formula in effect assumes an “average” bullet form. That's fine as long as you are shooting a “average” bullet. OU812's bullet has a sharper-than-average point. That sharp point adds significantly to the length but adds little to the mass or to the moment of inertia. Perhaps that throws off the calculations?

Bottom line: theoretical models are not perfect. If your gun likes the bullet, that's all that matters .... until the weather changes. :D

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CBA Member

frnkeore posted this 28 May 2016

I've posted this twist calulator before. If you study it's results, it will explain some things about why things happen to the stability of bullets.

The Miller formula does not solve for thr CG (meplat/nose shape & length)of the bullet, this one does and also shows what happens when the bullet is shot in the subsonic range. It's the only one, that I know of, that does that.

If you work with it, you'll find that long spitzer noses, require less twist. Not a huge amount but, it shows the trend.

http://www.geoffrey-kolbe.com/barreltwist.htm

Frank

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CBA Member

joeb33050 posted this 28 May 2016

Ken Campbell Iowa wrote: although it would still be of interest if the modified 80 gr bullets would stabilize in a 12 ( or 14 !!! ) twist ....even in a lowly 223 ....

besides ....it still appears that john a. has the only accurate cast bullet 223 rig in the world ....;. let us lower the bar to 2 moa groups ... anyone... ??

YESTERDAY, 22-250, STRIKER PISTOL, 225646M, 7/TITEGROUP, 100 YARDS, 10 FIVE SHOT GROUPS AVERAGED 1.613". I believe that I can now reliably shoot the pistol under 2” groups and the/a rifle around 1.5” groups. It seems that Savage 223 barrels won't shoot cast bullets accurately. It seems that Savage 22-250 barrels-with 1 exception-WILL shoot cast bullets accurately. With second hand 22” light sporter barrels, I'm happy with ~ 1.5” 5 shot averages. Soon we'll know if a 223 9” twist Savage barrel rechambered to 22-250 will shoot cast bullets accurately.

ken

speaking of 223 cartridges, has anyine achieved 1.5 moa ... or 2 moa.... from a 300 blackout cast rifle ?? this is getting kinda spooky ...

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mtngun posted this 28 May 2016

Joe, thanks as always for posting REAL SHOOTING DATA. :dude:

It's late at night as I type so I don't have time to go into detail but: -- forget Greenhill -- embrace Miller -- Miller merely requires an SF > 1.0 to stabilize, not 1.3. -- most simple Miller calculators treat all .89” long, 76.5gr, 22cf bullets the same, but in reality they are not all the same. Shortening a bullet by filing off the pointy tip changes the stability less than shortening the same bullet by filing off some of the check shank. -- In another thread, Paul Pollard mentioned that the JBM calculator could distinguish between the stability of a pointy bullet vs. the stability of a flat point bullet, if I understood Paul correctly.

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mtngun posted this 28 May 2016

OU812 wrote: Been holding off until I receive my new Leupold 45 power target scope. I received scope today You lucky dog! :fire Let us know how you like the Leupold.

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Ken Campbell Iowa posted this 27 May 2016

although it would still be of interest if the modified 80 gr bullets would stabilize in a 12 ( or 14 !!! ) twist ....even in a lowly 223 ....

besides ....it still appears that john a. has the only accurate cast bullet 223 rig in the world ....;. let us lower the bar to 2 moa groups ... anyone... ??

ken

speaking of 223 cartridges, has anyine achieved 1.5 moa ... or 2 moa.... from a 300 blackout cast rifle ?? this is getting kinda spooky ...

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CBA Member

gpidaho posted this 27 May 2016

Joe: It would be my pleasure to help out in anyway I can in your 22cal. quest. I measured (three times) my Savage 112 (26” heavy barrel) this morning and sadly it seems to have a 14” twist. While this might be a good thing with the 55gr or smaller bullets it will be of no help with the long 80s. I'll put together some loads to chronograph anyway as this will give you another reference point. I'm going to keep working on the 227-80s in my 223s. I have 8", 9” and 12 inch twists to work with there. I've enjoyed watching this thread and what you and OUB12 are doing with this extra long bullet. Gp

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joeb33050 posted this 27 May 2016

gpidaho wrote: Joe: I'd be happy to put a couple of chronograph strings together for you using the 227-80s. I have Titegroup and Blue Dot on hand and the IMR 4227 is available at local shops. (shot mine up in my 41mag) Send me a range of charges you'll be using and I'll send them over the screens for you. This will get me away from toying with the Blackout and back to the 22s again. Enjoy the day. GpIf you have a 12” twist 22-250, and if ob812 sent you 8-10 of his bullets, and if you loaded them over 7/Titegroup and shot them, we'd know if they stabilized in your/another 12” twist barrel.

joe b.

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joeb33050 posted this 27 May 2016

Blue Dot 5.5, 6.5, 7.5 gr. Titegroup 5.5, 6.5, 7.5 gr. IMR4227 9, 10, 11, 12 gr.

Thanks; joe b.

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OU812 posted this 26 May 2016

joeb33050 wrote: Everything we know tells us that a .89” long 77.5 gr .224 bullet won't stabilize, other bullets very close DON'T stabilize, OU812's DO stabilize. Is it the LBT blue?

I tried the longer original 80 grain bullet using LBT lube and it “would not stabilize", so it is not the lube. I also tried this longer bullet using HI-TEK coating and bullet would not stabilize in the same 1-12 twist barrel.

Again...bullet shot well after I trimmed .035 off gas check shank

...

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OU812 posted this 26 May 2016

Joe,

I plan on chronographing this bullet using a few different powders (bullseye, titegroup, bluedot, AO, 5744). Been holding off until I receive my new Leupold 45 power target scope. I received scope today along with new Burris 30mm Signature rings. This scope was a big investment and would not have been possible without large 2015 tax return.

I will send you more bullets to test soon (next Monday)

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gpidaho posted this 26 May 2016

Joe: I'd be happy to put a couple of chronograph strings together for you using the 227-80s. I have Titegroup and Blue Dot on hand and the IMR 4227 is available at local shops. (shot mine up in my 41mag) Send me a range of charges you'll be using and I'll send them over the screens for you. This will get me away from toying with the Blackout and back to the 22s again. Enjoy the day. Gp

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joeb33050 posted this 26 May 2016

gpidaho wrote: So Joe, only two of mine even hit paper? Guess no need to offer to send ya more. lol Hope it was just that long bullet in the slow twist and not a total reflection on my casting ability. Thanks for the report. GpAgain, it's about stability. Mine and yours are going through the paper sideways. Also, I've shot almost 500 22 shots with aluminum gas checks, and accuracy is very poor. Others say aluminum checks shoot fine.

Everything we know tells us that a .89” long 77.5 gr .224 bullet won't stabilize, other bullets very close DON'T stabilize, OU812's DO stabilize. Is it the LBT blue?

Was gebst?

Do you have any chronographed velocities with the 227-80 and Titegroup, IMR4227, or Blue Dot?

Thanks; joe b.