Why is .22 LR "standard" twist 1:16?

[FatJackDurham]

Why is the standard .22 LR twist rate 1:16? According to the twist rate calculator, that is useless for just about every factory load out there.

I bought a pile of 22 S,L and LR ammo to test in my newly relined Stevens for this coming weekend, and for fun, I pulled out the bullets and measure them. Then, I popped them into a spreadsheet with the twist rate formula to determine the minimum velocity for the bullet length to stabilize.

What I found was that for all the bullets, the required velocity was rediculously over the printed FPS on the box.

For example, a 40 grain CCI standard velocity bullet measured .470 in length. Even assuming the bore diameter was .223, which is unlikely to be more than .221 or .222, the minimum velocity to stabilize is 2029 fps, a ridiculously unattainable velocity. Only the smaller bullets seem to make the grade.

Is this why Paco Kelly invented his rimfire tool?

The only production rifle I found with better twist rates is a Remington model with a 14.25. And, of course, you can buy custom twists for the 10/22 from various sources.

So, what's the deal here, does the formula not apply at the .22 caliber?

[Hobie]

Bumblebees shouldn't fly and I suppose .22 LR bullets shouldn't fly true, but they do. So you applied the Greenhill formula and found that? Interesting.

[FatJackDurham]

Yes. I believe its the greenhill formula. I checked it with this website:

http://www.tmtpages.com/twistrate.htm

The bumblee bee analogy is apt. I wonder if that formula works better for a range of bullets diameters, but less so for the extremes.

I see that there are 1:9 twist bullets designed specifically to shoot the Aquila SSS Sniper round, so there must be something to it.

I don't know. I'll be shooting 14 different 22 ammos this weekend with my chrony, so I hope to get some good data.

[Mescalero]

A journey of discovery........... you Will be surprised.

[AJMD429]

The bumblee bee analogy is apt. I wonder if that formula works better for a range of bullets diameters, but less so for the extremes.

I think there's a "Dell" formula that takes more factors into account than the Greenhill one (maybe saw that on the LASC website, but don't remeber for sure).

Actually - found the link - http://www.lasc.us/Brennan_2-3_Twist.htm

I do know that the Aquila SSS's are NOT approved for use in some suppressors unless the barrel has unusually fast twist, because they supposedly can start keyholing before they even get past the suppressor, resulting in baffle-strikes.

Sounds like your range/chrony session should be very interesting. . . Range Report encouraged...!

[3leggedturtle]

Learn something different everday. How about the 50gr 22Mag Federal load. Any one know how long that bullet is and what speed it should take to stabilize? I chrono them at 1550fps out of a 19 and 21" barrel, and 1425fps out of a 10" Contender.

[1894c]

great discussion...great question...always wanted to know the reason why too...bumble-bees--go figure... :)

[iceman]

Bumble bees can fly because nobody told them they can't.

[Larkbill]

Standard .22 LR dia. is .219

Going further, how come my Ruger SSS is VERY accurate shooting .22 LR even though it's dia. is a compromise to enable it to also shoot .22 mag whose standard dia. is .223?

[Don McDowell]

This is one of those things where you can actually try to think yourself into a problem that doesn't exist.
The 22 was popular as a 200 yd target and small game cartridge right from its inception and it remains fully capable of still doing those things today.

The reason you can get reasonable accuracy from an oversized bore is quite simple, the bullet "bumps up" to fit the bore when the cartridge goes off. The little 22 lr runs at pressures that are actually somewhat amazing for such a little dude. So as long as you are getting good accuracy there's little to do but keep the chamber clean, especially the rim recess and the firing pin, but when accuracy starts to fall off then it's time to deploy your best lead mining technique, as the throat will likely have been filled with lead caused by the blowby.

[L_Kilkenny]

I'm curious what the greenhill formula or the spreadsheet, whatever, says about how well the lightweight hypers like the stingers should shoot in a 1:16. Because from experience it's a rare gun indeed that will print Stingers and their similar brethren worth a spit and I've always credited this to the twist rate not being acceptable for a 32gr bullet going 1600fps. But to monkey up the works this formula might seem to indicate that these lightweights should actually shoot better. Something we all no isn't the case.

LK

[mikld]

Bumble bees can fly because nobody told them they can't.

An aside; my favorite quote is from Garfield (the cat), "It is amazing what one can accomplish when one doesn't know what one cannot do..."

[FatJackDurham]

Wow! So many great questions!!!

I'll have to check that other link to see the formula.

One issue I have with Greenhill is that I don't know what the constant is based on. There is a simpler formula, but that doesn't take velocity into account.

Over the last three weeks, (so not an expert) I have reread articles on stability and accuracy. My dangerous limited knowledge so far is this:

1) Length vs. spin affects stability because of the leverage of the wind resistance against the tip of the bullet. Effectively, the longer the bullet, the further from the Center of Gravity is the tip. There for, the more leverage the air has to upset the bullet if flight. Once the bullet starts to tip, lift forces can change the path of the bullet.

2) Transonic boundary - A low velocity bullet can be more accurate over distance because it it doesn't cross the sound barrier in flight. The BC of a .22 bullet is so low, that even though a Stinger starts out faster, it ends up at the same speed. Crossing the transonic boundary in between destabilizes the bullet.

For example:
Bullet Muzzle 100 yards
Stinger 1640 1066
Standard 1070 908

Starting difference= 570
Ending difference= 150

But, the standard velocity bullet doesn't ever cross a sonic boundary.

3) For the magnum question, I am not sure what the actual length of the bullet is, but interpolating between the 40 and 60 grain, lets say it's .585. The formula says you'd need 2900 FPS for 1:16 twist, but only 1000 for a 1:9 twist. (rounded up). A perusal of forums showed me a couple of posts where 1:12 twist on a WMR could shoot up to a 55 grain bullet and a 1:9 up to 70.

4) The size of the .22 bullet is so small in length and diameter, that even a .001 change has vast effect on the result, there for, I suspect the margin of error is to high to use the formula effectively.

5) Overthinking - Obviously. One of the most impressive things I found reading these books is that there is very little that you can CALCULATE regarding shooting guns. Nearly the only way to know something for sure is "Trial, Error, Correction."

[AJMD429]

One of the most impressive things I found reading these books is that there is very little that you can CALCULATE regarding shooting guns. Nearly the only way to know something for sure is "Trial, Error, Correction."

The shooting part (trial, error, correction) is sure a heck of alot more FUN than the calculating part...

[FatJackDurham]

http://www.schuemann.com/LinkClick.aspx ... 67&mid=445

here is a good article on the whys and wherefores of bullet twist.

Summary: Accuracy is best at the minimum twist rate that can acheive stability.

[Hobie]

I want to further muddy the waters with a personal observation concerning the Aguila SSS with the 60 gr. bullet.

I have tried that ammo and it keyholes in every .22 LR gun I have but one. My 1956 Marlin 39M shoots it right well. Frankly, I only discovered that because, after trying it in every other gun I'd given up on the ammo but still had a bit to get rid of and the Marlin just happened to be the gun I had with me that day.

[retmech]

The Greenhill formula as I understand it was based on artillery shells. For rifles it's a very rough guide. An excellent example I've run across personally is two different 158 gr bullets by Lee in the Rossi 92 with 30" twist. The Lee tumble lube SWC 158 gr is stable and very accurate out to 200 yds (farthest that I've shot it) at 1100 fps. The Lee 158 RNFP will not stay on a 2' x 4' target backer at 100 yds due to tumbling at the same velocity and at 50 yds it will group under 2". The SWC is .660" long and the RNFP is shorter at .637" and these results are identical in 2 rossi .357's
! You pays your money and takes your chances!

BTW the RNFP at 1100 fps out of my Winchester 94 (16" twist) is very accurate at 100 yds as is the SWC.

[Dewight]

Because that is what works!

[Canuck Bob]

Fryxell discusses the formula regarding the 444 under the sub heading cast bullets for the slow twist MG barrel. He suggests a change in the constant due to his experimental results with heavy bullets. Personally I always got outstanding accuracy with my 444 when it was scoped and have been wondering for awhile if it wasn't the twist.

http://www.lasc.us/Fryxell444Marlin.htm

[FatJackDurham]

I want to further muddy the waters with a personal observation concerning the Aguila SSS with the 60 gr. bullet.

I have tried that ammo and it keyholes in every .22 LR gun I have but one. My 1956 Marlin 39M shoots it right well. Frankly, I only discovered that because, after trying it in every other gun I'd given up on the ammo but still had a bit to get rid of and the Marlin just happened to be the gun I had with me that day.

Interesting. The Marling has Microgroove, right? I wonder if that had an effect on the 60 grain bullet?

[Hobie]

I want to further muddy the waters with a personal observation concerning the Aguila SSS with the 60 gr. bullet.

I have tried that ammo and it keyholes in every .22 LR gun I have but one. My 1956 Marlin 39M shoots it right well. Frankly, I only discovered that because, after trying it in every other gun I'd given up on the ammo but still had a bit to get rid of and the Marlin just happened to be the gun I had with me that day.

Interesting. The Marlin has Microgroove, right? I wonder if that had an effect on the 60 grain bullet?

I don't know but supposedly the twist rate is the same... HOWEVER, I understand that one can get slightly different twist rates from the same tooling in successive barrels depending on the feed rate of tool/work. Perhaps the twist rate of this particular barrel is just fast enough...

[Mescalero]

Yes,
Hobie, there are a number of things that affect this, speeds& feeds; something that in my day
you were NOT allowed to step foot into the shop if you did not understand.
Wear in the tooling,if you do not " drop the knee " before you reset in milling operations you can not control the wear & slop in the lead screw, which controls fine feed.
I could go on forever, the misconception that there exists a " constant " is the most prevelant misconception.
The ONLY constant is the variable.

[1894c]

this thread has been very interesting thank you all for posting... :)

[Hobie]

Yes,
Hobie, there are a number of things that affect this, speeds& feeds; something that in my day
you were NOT allowed to step foot into the shop if you did not understand.
Wear in the tooling,if you do not " drop the knee " before you reset in milling operations you can not control the wear & slop in the lead screw, which controls fine feed.
I could go on forever, the misconception that there exists a " constant " is the most prevalent misconception.
The ONLY constant is the variable.

A collorlary is, "the only thing you can count on is change".

[Canuck Bob]

I own a couple of slow twist rifles. The micro groove 444 and Winchestr 32 Special. Pundits are always advising they won't stabilize heavy bullets. Handloaders are always stabilizing heavy bullets, must be magic, couldn't be the formula!

It is kinda like the statement, the 30-30 is under powered on deer (gun writer). My only rifle is the 30-30 (old farmer with 30 sets of deer and moose antlers nailed to the barn and sealers of bear grease in the pantry).