.223 rifle twist: fact vs fiction

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adcoch1

adcoch1

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Hello all, I am thinking about a 223 bolt gun, and I can't seem to get a satisfactory answer to a few questions.

Question 1: what is the heaviest bullet that can be universally accurate in a 1:12 twist.

Question 2: what is the most accurate combination of twist to bullet weight.

So, I have owned several ar 15 rifles and carbines, all with 1:9 & 1:7 rifling. All have been impressive accuracy wise, but I have heard a lot about 1:10 and 1:12 guns being quite accurate in bolt guns. I am leaning towards believing that the high quality bullets in the 62-69 gr weight may just be more forgiving than other offerings. I've just started reloading for 223, so I want to get some solid data before i go shopping for a rifle.

So that's the back story, tell me about your experiences shooting the 223, and lets try to keep it scientifically accurate, not just the usual "1:7 is the best" line i always hear, unless it's absolutely true. All my present 223 firearms ARE 1:7 btw...

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My cousin bought a Browning with 1:12 twist. I got the CZ with 1:9 twist. The Browning was key-holing 62 grain bullets. Don't get me wrong, nothing wrong with the rifle, just the wrong twist rate for what he was shooting through it.

I have shot 35 grain out to 75 grain. All were just fine at 100 yards. But, just because it looked good at 100, doesn't mean the 75 grain would look good at 200. From my understanding a 69 grain is a reasonable limit for 1:9 twist.

75grain.png

68grain.png

CZ527_HANDLOADS.png
 
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adcoch1:

Twist rates affect bullet stability based on bullet diameter, length and velocity. Weight has much less to do with it. With the 5.56 Nato cartridge, a stubby 75 grain flat base round nose bullet may have greater stability in a 1 in 9" twist than a pointy, (but longer) boat-tail bullet of 60 grain weight at the same velocity. Check out the greenhill calculator but note that specific gravity of the bullets composition figures in as well. http://kwk.us/twist.html
 
Question 1: what is the heaviest bullet that can be universally accurate in a 1:12 twist.
Click to expand...

It's a matter of length, not weight. Barrels that shoot 62 gr. spitzers just fine may not stabilize M855, which is longer than a pure lead core bullet because of the steel penetrator.

Generally speaking, though, 1:12 may not reliably stabilize bullets heavier than 55 or 60 gr.

Question 2: what is the most accurate combination of twist to bullet weight.
Click to expand...

If the bullet is stabilized, it's stabilized. There is a minimum RPM to stabilize a given bullet, and a maximum RPM the bullet's jacket can handle before it deforms or comes apart. Any RPM between those two will have no impact on accuracy.
 
sirgilligan said:
My cousin bought a Browning with 1:12 twist. I got the CZ with 1:9 twist. The Browning was key-holing 62 grain bullets. Don't get me wrong, nothing wrong with the rifle, just the wrong twist rate for what he was shooting through it.

I have shot 35 grain out to 75 grain. All were just fine at 100 yards. But, just because it looked good at 100, doesn't mean the 75 grain would look good at 200. From my understanding a 69 grain is a reasonable limit for 1:9 twist.
Click to expand...

Like you OP, I don't fall into the automatic 1-7" twist crowd.

Straight from the folks who know:

Sierra_zpsyeo8zttu.gif

I had one old Remington 788 in .222 with a 1-14" twist and it shot 60 Hornady SP's fine, as in 5-shot groups under 1" @ 100 yds. 60 gr. Nosler Partitions though, not so much. Bear in mind, just because a barrels twist is too slow doesn't automatically mean bullets keyhole. The .222 I mention shot the Partitions into 2 1/2" groups, but no tumbling at all.

Years ago my Dad had a .222 Remington Magnum built and ordered a barrel blank with a 1-12" twist so he could shoot 60 gr. bullets. Of course this was years before the internet and the assumption that a 1-7" twist is a one-size-fits-all.

Remember, in the longer barrels typically associated with bolt rifles, higher velocity is achieved thereby somewhat lessening the need for a faster twist. As an example, my Remington 700 Classic in 220 Swift has a barrel with a 1-14" twist but shoots the long-ish 60 gr. Partitions just fine...mainly because they're running a hair over 3600 fps.

35W
 
The history of .22 centerfires as I recall it:
For some decades, varmint hunters and benchrest shooters were happy with 52 gr boattails and 55 gr flatbase spitzers in 14" twist. There were heavier but short and blunt bullets that would shoot in a 14" twist, the 63 gr Sierra and the 70 gr Speer if you wanted to try the smallbore on bigger animals.

Then the military got into the act. They settled on a 55 gr boattail. It did ok in the 14" twist until they took it to Alaska. They went to a 12" twist for stability in cold dense air.
The Marine rifle team put on some 10" twist barrels to try to get better accuracy from the rather rough ball ammo.

Target shooters started working with the Mattel, it didn't kick and once the free floated foreend was devised, did not have the stock bedding requirements of M1 and M14. Sierra and Hornady obliged with 68-69 gr boattails that called for a 9" twist but shot closer to the wind.

The military found itself needing to shoot at foreigners at greater ranges and adopted the 62 gr three piece European SS109 bullet in M855 ammo. A 9" twist would have been adequate but the Army wanted tracers and it takes a very long .224" bullet to hold enough tracer mix to carry very far. That brought about the 7" twist.

Target shooters wanted higher BC for less wind drift so the bullet companies came out with 75, 77, 80, and 82 gr boattail match bullets. If you are lucky, your 9" twist might shoot the 75s well, but a faster twist is a safer bet and needed for anything heavier/longer. So we see twists in the 7.5" to 8" range.

You can really go nuts and load 90 gr bullets in a 6.5" or 7" twist barrel, I did, but that is probably getting to the point of diminishing returns. I wouldn't do it if starting over.

So, after 80 years history, what is your rifle to be FOR?

I think I covered No 2, and I think the 12" twist would be great for anything up to 55 gr and you might could do ok with a 60 gr flatbase.
When the heavier bullets were still kind of a novelty, C.E. Harris wrote that while the 69 gr bullet demanded a 9" twist, his was still more accurate at 100 yards with a 52 gr.
My 6.5" twist barrel, bought for 90 gr bullets will shoot 75s very accurately... if I don't load them to such high velocity that they spin apart.

Lots of flexibility below the high end.
 
Guys, this is exactly the kind of points, info, and discussion I was hoping for. I've been around guns and using them to good effect for a long time, but I've already learned a bit and heard a few things to think on! I really want a new cz527fs, but i have to justify its accuracy potential before i drop the cash on it, once i find one. There are lots of viable rifles for 223, so I figured it would be good to learn as much more as possible before purchasing anything else. Gotta read through this all again...

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The full stock rifles are stylish, but even though CZ says "muzzle cap designed not to bind on the barrel during expansion and contraction." I would not expect the greatest accuracy. I know my Sako Vixen Mannlicher was not as accurate as I hoped. I should have bought the sporter or heavy barrel.
There is a long thread here about a guy's efforts to get a full stock bedded uniformly enough to give decent accuracy.
 
I have a mini Mauser with a 1:12 twist. It shoots 50grain bullets under an inch, but when you move up to 55grn the groups open up to 3-4" at 100yds. I have not tried anything heavier.
 
That is more than likely one of those individual gun - ammo compatibility matchups.

MY 12 twist is more accurate with a 60 grain bullet while MY 9 twist is more accurate with a 52. Stability does not guarantee accuracy.
 
I have bullets that are fine in a 1:12 barrel that will come apart in a 1:7 barrel due to centrifugal force and bullets that will be fine in a 1:7 and tumble out of a 1:12.

So I would say it's fact, depending on what your trying to do.
 
1:7 was designed for stabilizing tracers which are really long and low density. It serves no other purpose. You will find most match grade barrels in 1:8 or 1:9.

Look at what the military itself uses for designated marksman rifles:
Army SDM-R 1:8" 20" bbl
Seal Recon Rifle: 1:8" 16" bbl
Marine SAM-R: 1:7.7" 20" bbl (started out at 1:7" but slowed to 1:7.7" for heavy bullets)
The Navy MK 12 SPR is the lone exception at 1:7"

I go out of my way to find 1:8 barrels when I build. If you are going to shoot a lot of light stuff and you are never going to shoot heavy and low density (all copper, for example) 1:9 might be best.

If you look back at the history of the M16 1:14 tumbled in flight, 1:12 didn't stabilize 55gr in cold weather!

Mike
 
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My AR-180 is 1/12. Only 55 grain will stabilize in it. I have had great results with the MK262 (77 grain) in 1/9, 1/7, and 1/8 twists. 10" CQB barrels up to 20" barrels.
 
My experience: I shoot a Remington 700 VSF .223 with 26" fluted barrel and 1:12 twist. I shoot prairie dogs up to 300 yards, but mostly around 200 + or - a few yards. I use 40, 50 and 55 gr bullets, all with superb accuracy. What I read is that the most popular weight for my rifle is 55gr, but I've never tried heavier bullets. The most accurate for my purpose (prairie dogs) is the Sierra 50 gr Blitz Kings. But, last weekend I wanted to use up my 40 gr Hornady V-Max and shot about 200 of them. So, zeroed my rifle for that ammo and killed lots of dogs with few misses. I prefer the performance of the 50s with fewer flyers, rare in fact. Let us know what you end up with.
 
A 222 I have with a 1:12 twist likes Speer 70 grain Semi Spitzers.

A 223 I have with a 1:10 twist puts 5 shots of Nosler 77 grain BTHP bullets into about .7 inches at 100 yards.
 
My son's Savage model 12 BVSS with a 1:9 30" heavy barrel shoots anything between 55g and 69g with absurd accuracy. Heavier than that and I've yet to find a load that works.

Case in point, 10 shots each at 100 yards, 55 VMAX on left / 75 AMAX on right

14DAE5ED-F7EB-4773-B0EF-1262449F0CB5.jpg
 
My son's Savage model 12 BVSS with a 1:9 30" heavy barrel shoots anything between 55g and 69g with absurd accuracy
Click to expand...

I wouldn't call 1-2 MOA with varmint and match bullets "absurd accuracy". More like run of the mill sporter accuracy. Not being snide, just the way it is. Most any half decent bolt gun can manage ~MOA @ 100 with decent ammo, and target/varmint guns should be able to hold sub MOA. My factory Ruger M77 Varmint in .220 swift averages .72 MOA @ 200 with 50 gr. V max bullets, and my 700 VLSF .17 rem is slightly better at .67 MOA with 25 gr Hornady HPs. The .220 has taken praire dogs at nearly 800 yards, though my hit:miss ratio at those distances is about 1:6.

This target was printed at 118 yards with my 22" bull barrel AR using 50 gr. V max handloads:

101_1456.jpg

It has a 1:8 Wilson Arms tube

bd303097-1d0f-45d9-bc3d-fb9d8929e2fe_zpssa2gzs98.jpg
 
Nature Boy said:
My son's Savage model 12 BVSS with a 1:9 30" heavy barrel shoots anything between 55g and 69g with absurd accuracy. Heavier than that and I've yet to find a load that works.

Case in point, 10 shots each at 100 yards, 55 VMAX on left / 75 AMAX on right

14DAE5ED-F7EB-4773-B0EF-1262449F0CB5.jpg
Click to expand...

The group on the right is a perfect example of a twist that's a bit too slow. NOTICE, the bullets ARE NOT tumbling, they just don't group well. This is why I think to myself "BS" when someone says 62 gr. lead core bullets tumble out of their 1-12" twist or 75's tumble out of their 1-9".
A buddy of mine coaches our 4H High Power team and told me some of the kids rifles with 1-9" twist will stabilize the Hornady 75 gr. HP, but not the A-Max.

35W
 
some of the kids rifles with 1-9" twist will stabilize the Hornady 75 gr. HP, but not the A-Max.
Click to expand...

Yup, it's the length.
My 14" twist .22-250 will shoot the Hornady 60 gr SP accurately but is just wild with the longer 60 gr HP. Not so bad as to keyhole, but barely on the paper.
 
Sniper66 said:
My experience: I shoot a Remington 700 VSF .223 with 26" fluted barrel and 1:12 twist. I shoot prairie dogs up to 300 yards, but mostly around 200 + or - a few yards. I use 40, 50 and 55 gr bullets, all with superb accuracy. What I read is that the most popular weight for my rifle is 55gr, but I've never tried heavier bullets. The most accurate for my purpose (prairie dogs) is the Sierra 50 gr Blitz Kings. But, last weekend I wanted to use up my 40 gr Hornady V-Max and shot about 200 of them. So, zeroed my rifle for that ammo and killed lots of dogs with few misses. I prefer the performance of the 50s with fewer flyers, rare in fact. Let us know what you end up with.
Click to expand...
Similar situation. Years ago I came upon a Remington I think it was a 725 in .222 Remington. Bad barrel but I had a brand new Remington 700 BDL VSSF barrel and put it on the 725 action. Using 55 grain and below bullets the rifle is a tack driver but anything above 55 grains I can't get good results with. Never had much luck with the lighter bullets in my 1:7 AR rifles.

Ron
 
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