223 at 1,000 yards

[Turbulent Turtle]

However, there is one parameter that isn't taken into account in many ballistic calculations and that is barrel twist rate, ie. bullet spin rate. After you mentioned inertia, it occurred to me that I had looked into the idea of fast twist rate affecting wind displacement several years ago. For reasons best left unmentioned, I had a .308 at the time with a 9-twist barrel that routinely gave me fits in terms of seeing much greater wind deflection than should have been expected for given wind conditions. Sure enough, Bryan Litz had a section on this topic in his first book, a phenomenon commonly known as "aerodynamic jump". In my hands, the difference in wind deflection between two rifles with essentially identical barrels (except for twist rate) using the same load was definitely noticeable at longer distances.

People typically run the 185s in something like a 12- or 11-twist barrel, and most are running the 90s out of 7-twist barrels. Because many ballistic calculators don't take the twist rate into account, I wonder if the dramatic increase in spin rate of the 90 VLD as compared to the 185 could account for the increased wind deflection you observed (via aerodynamic jump), even though the BC of the two bullets is almost identical. Along those lines, how did your predicted drop at 1000 yd based on known MV for the 90s match up with the actual drop? If it was fairly close, that at least would suggest that the BC reported for the 90 VLD wasn't way off.

An interesting post. So I pulled out the formula, plugged it into a spreadsheet and did some comparisons.
My assumptions:
.224 SMK 90gr. Length: 1.171. Velocity 2800. STP. 0 ASL.
.308 Berger Jug 185r. Length 1.353. Velocity 2800. STP. 0 ASL.

The number on the left is the twist rate, the number on the right is the jump in MOA/MPH. A higher number means more susceptible to wind.

For the 90SMK:

6.5, 0.039
7, 0.036
8, 0.032

For the 185Jug:
9, 0.046
10, 0.043
11, 0.038
12, 0.035

It would seem that the 90SMK at 1:6.5 is about as susceptible to wind as the 185Juggernaut in a 1:11.

In a 10MPH wind at 1000 yards, the aerodynamic jump difference between a 1:9 twist and a 1:12 twist is about an inch. For a 1:6.5 twist versus a 1:8 twist it's less than 3/4 inch.

In the same wind, the difference between a 90smk in 6.5 versus the 185 in a 1:12 is less than half an inch.

I'm thinking this is inconsequential. Remember that even though a .224 bullet will spin faster than a .308 bullet, its diameter is smaller so the angular velocity (I think I have the term right) difference is less than you would think.

 

[Turbulent Turtle]

The one thought that I had, in reference to inaccuracy at longer range for the 90gr is that perhaps there is some dynamic instability manifesting itself due to the high spin rate.

It would be interesting to know at what distance this becomes apparent.

As for the transonic area, that is usually from Mach 0.95 to 1.25 but I'm sure it can vary a bit, so your numbers show that you are comfortably above that area.

However, it could be that the BC used is "optimistic", which could account for greater wind deflection and lower velocity at the target, as in solidly in the transonic area.

As I said earlier, I only ever used the 80gr SMK but mostly JLKs at the 1000 yards after briefly playing with the 75 A-max. The 80s did pretty good but there were nowhere near the performance of my 180 JLKLBTs.

Finally, I just pre-ordered Bryan's latest tome. Talk about coincidence.

 

[Laurie]

I used a 223 with the Berger 90 VLD to get 7th place overall in the 2011 GB League FTR division. All GB League fixtures are LR bar the season warmer, an all 600 yard event. Of the remaining six rounds, four were entirely at 1,000 yards, one had 800/900/1,000 stages and one was 1,000/1,100/1,200 yards (which I skipped).

Fixtures were and still are held at Bisley, Diggle, and Blair Atholl, none of them known as 'easy' ranges. I took a lot of 1,000 yard stage 1st to 4ths that season, and the rifle shot a dream with elevations that were as good as my previous season's 308 shooting Berger 185s at 2,825 fps - and that was extremely good. I can't say I ever found Jerry's greater wind drift compared to the 308 at 1,000. That was with a 31-inch 1-7" twist and 2,907 fps MV for the Berger 90gn VLD. Incidentally in testing, I got two five-inch ish 5-round groups at 1,000 in a UK BR Association match, one each with the VLD and BT, the latter at ~2,860 fps. By that time, many GB FTR competitors had skipped the 185 Juggernaut and moved directly to the Berger 210s at 2,650 at least, often over 2,700 fps.

When shooting with and against the US F/TR team at Blair Atholl exactly three years ago this week, I won a 1,000 yard individual using the 90gn VLDs, and when we talk 'bumpy air', there are few ranges that have bumpier air than Blair. The rifle also produced the second highest score in a coached team shoot at 1,113 yards and (what TonyR likely remembers) shot 10 rounds in a low-wind condition practice before the weekend at the 1,200 yard point - actually 1,224 yards there. 9 ex 10 shots were within 0.5-0.75-MOA elevation, one a bit low and all bar a couple stayed inside the thousand yard target's four-ring, (ie well under 2-MOA) moving around a bit due to invisible wind. I can't remember the score, but it was in line with what US team members were getting with 155.5s at MVs that they wouldn't disclose, but were likely higher than most British FTR shooters were getting three years ago prior to the widespread adoption of Lapua Palma brass.

Sticking to Blair, notorious for its 'funny elevations', I briefly held the GB F-Class Assoc record for a 15-round 1,000 yard match score shot there with the 223, 74 and something like 9 Vs. As luck would have it I was squadded with Russell Simmonds, then World FTR champion and we shot alternately (two on the mound system used here with the 45 second rule - none of your string shooting waiting on a wind condition) and we tied on points but I beat him on the last shot to get an extra 'V'. Russell then shot 155s at well over 3,100 fps in his 308.

So, why don't I still shoot 223? FAR too much work in handloading, and EVERYTHING has to be right. The first barrel started to throw the occasional round low after just over 2,000 rounds went through it. Its replacement never shot as well and produced its best results at lower MVs. And as was quoted earlier, 2,900 fps is the magic number for the 90gn VLD for 1,000 yard shooting. I really believe that if you don't break that barrier, it won't perform consistently at 1,000. (At 600, the 90s can humble 308s at quite low MVs - I have a rebarreled Savage 12 LRPV with 26-inch Bartlein 1-7.5 that shoots tiny groups with the 90 BT at only 2,650 fps and is extremely effective in club shoots.) We now have some new powders coming to the UK from Nitro-Chemie under the Reload Swiss brand name including RS52, very like the N-C manufactured Alliant Reloder 17 (RS60) but with a similar burning speed to Re15 / VarGet. Running tests with a pre-launch sample, I easily broke the 2,900 fps barrier with Berger 90 VLDs in a 28-inch barrel and with less pressure than from the Re15 I'd used when 223 was my main FTR tool. So, who knows - I might be shooting 223 again next year!

In summary, try it if you fancy the idea. BUT, be prepared for a great deal of work and experimentation, very total likely disappointment and at best almost certainly severe frustrations. .308 is a much more sensible LR FTR choice, and offers far more flexibility now thanks to the large number of top class bullets introduced in recent years, mainly by Berger.

 

[Turbulent Turtle]

Holly crap. Thank you so much for posting his reply. It confirms something I've been observing empirically. I ordered his new book when it was announced earlier this week, but I'm glad to get this tidbit right now.

I've always believed that bullets that were not completely stabilized at the muzzle just could not have the best BC value for that bullet. So bullets that need time to "go to sleep," are in effect only reach optimum stability as the forward velocity decreases, since the spin rate remains the same and the overturning forces diminish.

I always believed a 1:11 twist was better than a 1:12 or slower for the bullets that I use, the long 180gr JLKLBT bullets. The 1:11 shoots then like laser and I get a trajectory quite close to predictions. I see that with a 1:11 twist, my Sg. is 1.67+ but with a 1:12 it would be 1.4.

 

[rcw3]

The whole discussion on "twist rate" gets confusing.

I see the pieces of quotes by Bryan Litz saying a 1.5 sg is best, but things just do not figure up.

Example: If you take the recommended twist rate for the Berger .224" 80 gr. VLD and the Berger 82 gr BT bullets, they have a recommended twist rate of 8".

But if you take the Berger calculator here:
http://www.bergerbullets.com/litz/TwistRuleAlt.php

Then run the numbers for an 8" twist barrel for a .223 Rem pushing either of them 2700 or so fps, you're going to come way under the 1.5 sg number that is suggested by him in the quotes (yet he presumably set the published twist rates for the bullets). So where does one go for a twist rate and what do you believe?

This one has me scratching my head.

Robert

 

[Turbulent Turtle]

The way I look at it, the 1:8 twist recommended by Berger will definitely stabilize the 82gr 1.115 inch long 82gr Berger at 2700FPS, STP, 0 ASL. The Sg is 1.32, which means the bullet will not keyhole and as the distance grows it will fully stabilize and "go to sleep." It's just that since it was not completely stabilized at the muzzle, it will have lost some velocity (lower BC) because it was not perfectly point on at the beginning.

The Berger 80gr Match VLD is a smidgen longer at 1.117 and at the same MV and conditions as above, it's Sg is 1.28. It will also be marginally stable at the muzzle and will go to sleep a little further down but it will not keyhole.

The recommended twist rate from Berger should be viewed as "minimum recommended twist rate." Or better yet, don't use anything slower in a twist.

Twist rate is a Goldilocks game of too fast, too slow and just right.

Too fast and in extreme cases you get little cylindrical puffs a few dozen yards downrange and nothing on target, or if the bullet is damaged or otherwise defective you get nasty dynamic instability.

Too little and in extreme cases you get keyholes on the target and at longer distances you miss the target completely, or the bullet stabilizes further downrange but you have lost extra velocity until it goes to sleep.

You want to get it just right for the long haul.

When specifying a barrel, pick your bullet, get the length, figure out the required MV to get to 1000 as much above Mach 1.25 as you can and pick the twist rate that will provide an Sg of 1.5 or somewhat better and then go out and enjoy.

 

[Laurie]

1-7" + 2,900 fps gives the 90gn Berger VLD an Sg of 1.35 using the Miller spreadsheet, and 1-8" + 3,000 fps gives the 80gn VLD / 80.5gn LRBT Sg values of 1.37 / 1.46 under standard environmental conditions. I neither saw, nor suffered any problems shooting 223 Rem at long ranges in much cooler / coldish UK weather conditions in real life match conditions throughout the winter months. One of my best results with the 90gn VLD was the final 2+20 1,000yd match at Bisley in the November 2011 European F-Class Championship meeting in difficult and strong winds and temperatures in the high 30s, low 40s F.

Likewise, I think all this stuff about bullets not stabilising until after so many hundred yards is pure bunk. My load development with these bullets was all done at 100 yards off the bench, and if the load didn't consistently put 5 rounds into 0.2-0.35 inches, it didn't make the grade.

1,000 yard real-life scope elevation adjustment come-ups from 100 yard settings were pretty close to those predicted for the G7 BC in Bryan Litz's PMII Ballistic Solver program, so the average BC over that distance was pretty close to Berger's / Bryan's value.

Having said why [maybe] not use 223, I didn't give the counter argument - if you get it shooting well, it's just so nice / easy to shoot in an 18lb FTR rifle. I never bothered with a fancy wide-foot bipod, simply using a pair of different height folding leg and locking-joint Versa-Pod tactical models.

 

[ptd]

I think I remember reading that original Miller formula underestimated stability a tad as it assumed constant density from base to tip? Would that not factor into what folks are observing vs calculating?

-pd

 

[Laurie]

I think I remember reading that original Miller formula underestimated stability a tad as it assumed constant density from base to tip? Would that not factor into what folks are observing vs calculating?

-pd

Yes, absolutely. Michael Courtney (who is a forum member) proved some time that Miller understates HP and plastic tipped pointed bullets' actual Sg values. I'm always very content with the relationship where the the Sg exceeds 1.3 with these bullets, and have successfully used combinations at long range in lowish but still above freezing temperatures with values much lower than that at times. (There are still some UK FTR 308 using competitors happily using 1-14 inch twist barrels with the latest generation of long 155s producing Sg values that should see bullets go through targets sideways!)

 

[JRS]

Here is a response from Bryan Litz:

Greg,

Thru recent testing, specifically on twist rate and stability, it’s been discovered that although bullets can shoot accurately with stability levels of 1.4, even down to 1.2 or 1.1, BC is not maximized until you achieve an SG of 1.5. So with an SG of 1.4, you’ll see about a 3% degradation in BC compared to getting the SG over 1.5, even though the bullets might appear to be fully stabilized based on accuracy.
Another thing is that transonic is a very gray area, with the heaviest affects coming at speeds below Mach 1.2, but you can see some effects at higher Mach numbers such as 1.3 or 1.4. There are even dynamic instabilities which can be observed at higher supersonic speeds (Mach 1.5+) which are not necessarily related to transonic, but other aerodynamic effects.
Long skinny bullets such as the 22 cal 90 grain bullets tend to suffer most from these effects.

My new book: Modern Advancements in Long Range Shooting, which will be available next month, goes into extensive detail on these recent stability tests. I think you and the others on that thread will be very interested in the material covered in that book.

Take care,
-Bryan

Kind Regards,
Bryan Litz
Ballistician
bryan.litz@bergerbullets.com


So it seems as though there could be several things that might contribute to the performance issues some have observed with the 90 VLDs at 1000 yd. It sounds as though they are largely due to the extreme length of this bullet. I will continue with load development and report my results (good or bad) here.

Nothing new ???

Randy Robinett explained the above quote by Litz to me a few years ago. It's the very reason I order a twist rate a bit slower than the current trend 8).

 

[TonyR]

When shooting with and against the US F/TR team at Blair Atholl exactly three years ago this week, I won a 1,000 yard individual using the 90gn VLDs, and when we talk 'bumpy air', there are few ranges that have bumpier air than Blair. The rifle also produced the second highest score in a coached team shoot at 1,113 yards and (what TonyR likely remembers) shot 10 rounds in a low-wind condition practice before the weekend at the 1,200 yard point - actually 1,224 yards there. 9 ex 10 shots were within 0.5-0.75-MOA elevation, one a bit low and all bar a couple stayed inside the thousand yard target's four-ring, (ie well under 2-MOA) moving around a bit due to invisible wind. I can't remember the score, but it was in line with what US team members were getting with 155.5s at MVs that they wouldn't disclose, but were likely higher than most British FTR shooters were getting three years ago prior to the widespread adoption of Lapua Palma brass.

That shoot with the 223 was something to see. On the line with some of the best 308 shooters in the world and holding elevation with the best of them. So it can definitely be done by someone with patience and determination. Probably not the best choice for just anyone, but some shooters can't take recoil for purely physical reasons such as shoulder injuries and it would be one way someone with physical problems could stay in the game.

 

[Turbulent Turtle]

1-7" + 2,900 fps gives the 90gn Berger VLD an Sg of 1.35 using the Miller spreadsheet, and 1-8" + 3,000 fps gives the 80gn VLD / 80.5gn LRBT Sg values of 1.37 / 1.46 under standard environmental conditions. I neither saw, nor suffered any problems shooting 223 Rem at long ranges in much cooler / coldish UK weather conditions in real life match conditions throughout the winter months. One of my best results with the 90gn VLD was the final 2+20 1,000yd match at Bisley in the November 2011 European F-Class Championship meeting in difficult and strong winds and temperatures in the high 30s, low 40s F.

With the Sg figures you listed, you would not see any problems shooting the 223 at those temperatures, the most you might see is the need for a little more elevation as the temperature drops. Some of that would come from the increased cold air density and some of it would come from the further reduction of the BC as the Sg decreases. Now, if you tell me that as it got much colder you didn't have to adjust for elevation, well then, I don't know.

Where I shoot most of the time, the problem is a little different as the temperature can increase 30 degrees or more between the first match and the last one. I find myself removing a little of elevation on the scope, usually about .25 MOA for 20 degrees difference but sometimes more.

Likewise, I think all this stuff about bullets not stabilising until after so many hundred yards is pure bunk. My load development with these bullets was all done at 100 yards off the bench, and if the load didn't consistently put 5 rounds into 0.2-0.35 inches, it didn't make the grade.

If your Sg was 1.3 and above, there would have been no manifestation of instability on the target as you bullet was "stable" at the muzzle. Bryan makes it clear the only thing that would occur is a slight reduction in the BC values (in the order of 3% at 1.4). This would have infinitesimal effect at nearer ranges and no effect on group sizes.

1,000 yard real-life scope elevation adjustment come-ups from 100 yard settings were pretty close to those predicted for the G7 BC in Bryan Litz's PMII Ballistic Solver program, so the average BC over that distance was pretty close to Berger's / Bryan's value.

Define "pretty close".

I did some calculations using my bullet and velocity, etc.
I shoot the 180gr JLKLBT @ 2850 (12 feet) with a G7 BC of .291 at 80f, 80%, 100ASL.

At 100% of the BC, I get a drop of 28 MOA at 1000 yards and 6.6 MOA of wind (10mph, full)
So:
At 100%, -28.0MOA and 6.6MOA of wind.
At 97%, -28.6MOA and 6.9MOA of wind.
At 95%, -28.9MOA and 7.1MOA of wind.
At 92%, -29.5MOA and 7.4MOA of wind.
at 90%, -29.9MOA and 7.6MOA of wind.

So "pretty close" was what? one and half MOA of elevation, two maybe. No biggie, you were on target, and maybe even in the black. Elevation is easy to compensate for, just turn the dial a little bit. But in our hypothetical conditions above, you will notice that you get a full MOA more of wind with a drop of 10% on the BC. With a 5% drop, something that is within the realm of probability at an Sg of near 1.3, you get an extra half MOA of wind to deal with. Something you could easily alleviate just by having a faster twist.

Anyway, that's how I understand Bryan's reply and it makes sense to me.

So, it's not about unstable bullets becoming stable when they "go to sleep," this is about a bullet getting into a more aerodynamic attitude and getting the maximum benefit of its BC. The bullets were never in danger of destabilizing or not being accurate right from the muzzle.

 

[Turbulent Turtle]

I think I remember reading that original Miller formula underestimated stability a tad as it assumed constant density from base to tip? Would that not factor into what folks are observing vs calculating?

-pd

Yes, absolutely. Michael Courtney (who is a forum member) proved some time that Miller understates HP and plastic tipped pointed bullets' actual Sg values. I'm always very content with the relationship where the the Sg exceeds 1.3 with these bullets, and have successfully used combinations at long range in lowish but still above freezing temperatures with values much lower than that at times. (There are still some UK FTR 308 using competitors happily using 1-14 inch twist barrels with the latest generation of long 155s producing Sg values that should see bullets go through targets sideways!)

I used the JBM stability calculator that accounts for plastic tips and it does make a difference in the Sg.

 

[Turbulent Turtle]

Randy Robinett explained the above quote by Litz to me a few years ago. It's the very reason I order a twist rate a bit slower than the current trend 8).

I fail to see the reasoning that supports your decision to order slower twist rates in your barrels. So, knowing all this you get a 1:13 instead of a 1:12 for a .308?

 

[jsthntn247]

Anybody ever try H4350 with the 90's? Seems some folks are having good luck with it and the heavies in 308.