Who's shooting 90 VLD's with a 1:6 twist barrel?

[Mozella]

Berger changed their twist recommendation for their 90gr VLD bullets to 1:6 a while ago. I notice that most guys report shooting them out of 1:7 or 1:6.5 (or similar) barrels. I can't find any first hand experience using a 1:6 twist barrel.

I talked to Berger today and told them I was thinking of buying a 1:6 barrel and I asked for their advice. I have tested the 90's at MVs as high as 3020 fps but normally I only shoot them about 2700 fps out of my 1:7 and my 1: 6.5 twist barrels which is significantly below the speeds most guys use. That give a spin of 324000 rpm. Berger said that rpm risks jacket failure and encouraged me to buy a 1: 6.5 or a 17 twist barrel and keep the rpm below 300000.

I mentioned that I've been there and done that without much success. Although my 1:7 and my 1:6.5 barrel will shoot some nice groups with the 90's, they are not nearly as consistent as what I get from other guns and/or bullet weights.

I don't know anyone launching .223 bullets as slow as 2500fps for 600 yd F/TR competition but that's the limit if you want to stay below 300000 rpm. According to the Berger rep I talked with today, I should keep the rpm at or below that.

So I asked why they recommend a 1:6 twist if the jacket is at risk for failure at MVs above 2500 fps. He didn't give me an answer. In other words, I couldn't get him to give me a single example of when a 1:6 twist barrel is appropriate even though that what they recommend. Strange.

So the question is this: Is anyone using a 1:6 twist barrel with the 90 VLD's? If so, are they careful to keep the MV below 2500 fps? Or, if they're using MV's up around 2700 fps, are they experiencing jacket failures?

 

[Ned Ludd]

A 7.0-twist is all you need to compete with the 90s. You will be giving up perhaps about 2% of the maximum theoretical BC of the 90 VLD, but it works just fine. You can also go with 6.5-6.7 twist in order to obtain the full BC under typical atmospheric conditions (65 degrees and higher, 500 ft elevation and higher). There is no need at all to use a 6-twist. If jacket failures are a potential issue at sufficient velocity and rpm, why spin them that hard? One thing I know for sure, I have no intentions of EVER running them at only 2500 fps .

One thing you need to remember about firearms industry personnel...being a "Rep" doesn't necessarily being an "Expert". In many cases, these folks are required to know at least a little bit about a very wide range of products, but they can't always be expected to have the same expertise on any given product as an individual that has been using that one product competitively for years. Sometimes you get lucky and run into a rep that really knows their stuff on the topic you're asking about. Sometimes they don't.

 

[swd]

One thing you need to remember about firearms industry personnel...being a "Rep" doesn't necessarily being an "Expert". In many cases, these folks are required to know at least a little bit about a very wide range of products, but they can't always be expected to have the same expertise on any given product as an individual that has been using that one product competitively for years. Sometimes you get lucky and run into a rep that really knows their stuff on the topic you're asking about. Sometimes they don't.

Boy, ain't that the truth!! This should be sticky.

In regards to the OP. It's sad that Berger has made a recomendation that doesn't match up with the real world. They know very well that probably 80% + of the 90's are being sold to guys shooting diciplines that will push them 2700+ fps.

 

[jsthntn247]

What are the specs on the rifle your having trouble shooting them in?

Barrel Length
COAL length of loaded round
What powder, primers, and brass have you tried?

Should be fairly easy to get a load that shoots half moa at 600 if done right. I have shot them at 2650, 2780, and 2850 with 3 different powders and shot HM scores.

Personally I would stick with the 6.5-7 twist

 

[Mozella]

What are the specs on the rifle your having trouble shooting them in?

..... snip.....

I've done a lot of carefully measured testing with VLD 90's, first in a Shilen 26" 1:7 twist barrel (175 rounds) and then in a 30 inch PacNor 1:6.5 twist (769 rounds). Each 5 shot group was scanned and carefully measured using On Target software and then compiled in M.S. Excel work sheets. I've tried MVs as high as 3020fps and as low as 2349fps. I tested with Varget, Vihtavuori N-140, Vihtavuori N-540, Reloader-15, IMR 4895, IMR 8208 XBR, CFE-223, and Vihtavuori N-550. As for primers, I've tested Federal Gold Medal Match, CCI BR-4, and CCI 450 Magnum. I've tried Lapua and Lake City brass. I've used jumps from a .015" jam all the way out to .080" jump in .005" increments. I've experimented with neck tensions between .0015" and .003". I've tested bullets out of the box as well as trimmed, pointed, and trimmed plus pointed.

So there's no lack of careful scientific experimentation. But I'm still searching for a 90gr recipe which is reliable.

The best 5 shot group at 100yards measured .107 MOA. Unfortunately, attempting to duplicate that exact recipe produced groups measuring .725 MOA under identical no wind conditions. Not all my best groups are that good or that bad of course. But the results show a frustrating inconsistency; i.e. one group is great and the next not so hot or even horrible.

This is not my first rodeo. I've been able to zero in on a dead-reliable load for several rifles which shoot well group after group. I've had particularly good luck with this same Shilen 1:7 twist barrel shooting Berger 80 VLD's. My best fifteen 5-shot groups using the 80's average an MOA of .239 and I could count on that kind of performance without worrying about any group worse than .500 moa, ever.

I don't need that kind of performance out of the 90's but I can't stand shooting four groups in the 3's and then a group of .700 MOA followed by a group of .900 MOA. That's why I'm still searching for answer 'cause I'd really like to figure out how to shoot the 90's.

I still win my fair share of 600 yd F-Class matches and 600 yard BR matches with my 6mm BR, so even though I'm getting older every day, I can still shoot well enough to have some confidence in my collected and carefully measured data.

I suppose the PacNor barrel might be a "non-shooter", but the best 50 groups of VLD 80's average .484" even though the barrel is chambered for 90's. That's not spectacular but, unlike the 90's, the performance of the 80's is reliable. I've won some matches with the PacNor too, shooting 80's.

I went ahead and ordered a 1:6 twist barrel just to satisfy myself that I'm not missing out because of insufficient spin. I'm still mystified about Berger's 1:6 minimum twist recommendation for their 90's if they worry about rpms above 300000. That still doesn't make sense to me. I'll know something in a few months when the barrel arrives.

 

[cb1229]

We followed Lauri Holland from England in target shooter magazine and he worked up a load using 25gr of re-loader 15 and 90vlds in a 6 twist running 2850 very accurate any hotter and the bolt starts to stick

 

[XTR]

I shot them from a 1:7 at 2800 and won SOA short range Agg in 2015 at Raton and took 3rd this yr at the Sinclairs East Coast Nationals at Butner. I run a 308 beyond 600 but the 223 w/90s will rock mid range.

Greg and I have both posted the formulas that work many times here.

 

[r bose]

To answer your question, Berger has to give worst case scenario for twist rate. Imagine a 20" service rifle being shot at sea level, shooting in sub 50 degree temps, at 2500 FPS?? Might need a 6 TW but no more than a 6.5TW....been there done that. Remember not every 90g 223 bullet is being shot out of an FTR rifle.

 

[raptor1ronin]

I use 1-6.7 twist. Great results however I have had Bullets blow up. Decided to go 1/7 haven't seen one blow up with that twist.

 

[cmillard]

Laurie Holland!! if I am not mistaken, he was successful with the 90s out to 1200 yards with a 7" twist?

 

[Snuggie]

I was shooting the 80 SMK's and 8208 XBR with a 7.7 TW and they shot very well. Went to a 6.5 TW and the 90VLD's. It's a LASER !! Running about 2,750 with Varget but recently had hard bolt pull back in 97 degree weather! Imagine that?!?! Having Gretan bush my firing pin hole and install his ( Greg's) fluted pin and spring.

 

[jsthntn247]

I was shooting the 80 SMK's and 8208 XBR with a 7.7 TW and they shot very well. Went to a 6.5 TW and the 90VLD's. It's a LASER !! Running about 2,750 with Varget but recently had hard bolt pull back in 97 degree weather! Imagine that?!?! Having Gretan bush my firing pin hole and install his ( Greg's) fluted pin and spring.

I was wondering if you got that figured out.

 

[Ned Ludd]

Laurie Holland!! if I am not mistaken, he was successful with the 90s out to 1200 yards with a 7" twist?

A 7-twist will work just fine, but you may not be getting the full [theoretical] BC of the bullet at that twist rate. I've used a .223 that has a 7-twist barrel with the 90s out to 1000 yd on a number of occasions and never had any issues. However, with the isolated reports of people having jacket failures with the 90s, it may not be advisable to use more than a 7-twist. I have a second (new) .223 with a 6.8 twist and had what I think was a probable jacket failure with the 90 VLDs in a recent MR match, which cost me a good finish. On paper, a 6.8 twist is just enough to produce an Sg of >/= 1.5 and get the full theoretical BC of the bullet. I may never know exactly what the root cause of that failure was, but once it happens, the possibility that it could happen again is solidly in your mind and that's not a good thing. So I think in the future I will likely stick with a 7-twist and call it a day.

 

[Snuggie]

I was wondering if you got that figured out.

Yep. I cleaned the hell out of it and then put three rounds thru it. Still same prob. Better soon though! LOL!!

 

[jsthntn247]

A 7-twist will work just fine, but you may not be getting the full [theoretical] BC of the bullet at that twist rate. I've used a .223 that has a 7-twist barrel with the 90s out to 1000 yd on a number of occasions and never had any issues. However, with the isolated reports of people having jacket failures with the 90s, it may not be advisable to use more than a 7-twist. I have a second (new) .223 with a 6.8 twist and had what I think was a probable jacket failure with the 90 VLDs in a recent MR match, which cost me a good finish. On paper, a 6.8 twist is just enough to produce an Sg of >/= 1.5 and get the full theoretical BC of the bullet. I may never know exactly what the root cause of that failure was, but once it happens, the possibility that it could happen again is solidly in your mind and that's not a good thing. So I think in the future I will likely stick with a 7-twist and call it a day.

Yea, cost you second place in a state match more than likely. Hated to see that happen. I've yet to have one fail in my 6.5 twist but it's probably a matter of time.

 

[Ned Ludd]

Yea, cost you second place in a state match more than likely. Hated to see that happen. I've yet to have one fail in my 6.5 twist but it's probably a matter of time.

That was certainly a possibility. Of course, if you'd shot the .223 both days, you'd likely have been right up there as well. Exactly where I might have finished isn't so important as the fact that it would have been much better than where I did finish . Even more important is trying to get a handle on why it happened, if that's even possible. It could be the twist thing, but I'm not at all certain that everyone that's had a 90 VLD fail before getting to the target all had the exact same cause. Drew is pretty certain it was a cleaning issue in his case. It may not be possible to ever really know for sure what happened in my case, but I'll keep trying and hope it doesn't happen again. As I mentioned, the first rifle has worked so well with a 7-twist, I just don't see the need to go any faster in the future, even if the faster twist rate barrels end up having nothing to do with jacket failures.

 

[284winner]

If the 90s are pushed between 3000-3200 will an 8 twist stabilize them ?

 

[Ned Ludd]

If the 90s are pushed between 3000-3200 will an 8 twist stabilize them ?

That's a good question. I've come across a few older posts here at A.S. where people were pushing the 90s out of .22BR and other similar cartridges in the 3000+ fps range that were using a 7.2-twist. According to Berger's Twist Rate Calculator, a 7.2 twist at 3100 fps would have an Sg of 1.41 and be giving up approximately 3% of the theoretical BC (calculator set at 75 degrees and 500 ft elevation). That is fairly close to what a 7.0-twist will give you with the 90s at .223 Rem velocities. At the same settings/velocity, the 8-twist is predicted to give and Sg of 1.14, and a reduction in BC of 11%. I'm nit even sure that an 8-twist would be sufficient to prevent keyholing (gyroscopic instability); it's pretty far down there in terms of Sg. So it seems as though you can buy a little twist rate forgiveness with increased velocity, but only a little.

 

[284winner]

That's a good question. I've come across a few older posts here at A.S. where people were pushing the 90s out of .22BR and other similar cartridges in the 3000+ fps range that were using a 7.2-twist. According to Berger's Twist Rate Calculator, a 7.2 twist at 3100 fps would have an Sg of 1.41 and be giving up approximately 3% of the theoretical BC (calculator set at 75 degrees and 500 ft elevation). That is fairly close to what a 7.0-twist will give you with the 90s at .223 Rem velocities. At the same settings/velocity, the 8-twist is predicted to give and Sg of 1.14, and a reduction in BC of 11%. I'm nit even sure that an 8-twist would be sufficient to prevent keyholing (gyroscopic instability); it's pretty far down there in terms of Sg. So it seems as though you can buy a little twist rate forgiveness with increased velocity, but only a little.

Just wondering what speed would allow stability in an 8 twist if any ? I've heard some guys saying that there 22-243 AI will stabilize the 90s at high enough speeds in an 8 twist barrel.

 

[Ned Ludd]

Just wondering what speed would allow stability in an 8 twist if any ? I've heard some guys saying that there 22-243 AI will stabilize the 90s at high enough speeds in an 8 twist barrel.

You can run the numbers using Berger's Twist Rate Calculator. Not sure how high velocity would have to be to get an acceptable Sg with the 90s out of an 8-twist, but it would be way up there...probably much faster than is realistically possible of an 8-twist at 3100 fps only gives a predicted Sg of 1.14. In my hands using twist rate calculators, it seems as though increasing velocity has a much smaller effect than does increasing twist rate.