You long distance guys; 6mm twist suggestions please for 75-87gr, and, 87-105gr

V

VaniB

New member
I want a 6x47Lapua varmint rifle to shoot accurately at 400-500 yards. To start with, I will test loads to be sure it can shoot 3/8" 5 shot groups at 100 yards.

I want a barrel to fire the 75Vmax-87Vmax bullets.... or a barrel to fire the 87V - 105Amax.

Some guys say that excess spin effects accuracy. I've also heard that a bullet shooting 1/2" groups at 200 yards can go to crap at 300 yards. You long distance shooters would know about this.

What barrel twists do you recommend I order for those two different bullet choices?
 
You'll need 8.5 twist to stabilize the 105's... 10 twist will do for the others (75-87).

Paul
 
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Hmmmm...

Benchresters seem to favor slower twists over those favored by those if us who shoot off the ground.

Those two bullet weights should work just fine in anything between 1:8 to 1:9, though if you want to choose one over the other go with the slower twist for the heavier bullet.

For mid-range high power, the 6mm shooters use bullets from 90 to 115 grain with twists from 1:7 (rare but possible) to 1:8. Few go any slower unless they choose to use bullets on the lighter end of this range.

If I were in your position I'd go with a true 1:8 for either weight range. Bartlein just shipped a 1:7.8 5R 30" barrel for me for a 6XC I'm having built for 1K this year. I plan to use either the DTAC 115 or the newer 111.
 
You will be happy with your 6X47

I have several now - all in 1-8 twist to shoot 100 gr + vld's and BT's

Couldn't get the 87gr to shoot well in the 1-8.

105gr+ with IMR4350 and RL19 are doing 3050 to 3100 fps - incredible accuracy with bergers 105/108, 105 amax's not far behind. Using 28 inch Kriegers. Using a no turn .272 neck. Use a full length forster 6x47 die with expander ball installed to size the brass the first time. Necks come out .2685, no ugly shoulder like I was getting when I did it with bushings. So simple, it's like cheating. I use it only the first time - figure necks wouldn't be concentric the first time anyway

Am building one now in 1-12 twist to shoot 70 to 80gr bullets, hoping to get good speed with a 70gr without brass stress. Flat trajectory rules for PD's

You can build a 1-10 twist to shoot the 87's, but my experience is that the 1-10 won't work great with the 100+ or >70 bullets. Another one to try if you go 1-10 is the berger 88. 1-10 might work with 75 vmaxes, don't have experience with that. Lighter is iffy.

Am a huge 6x47 fan.
 
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Try this...

Xcell I file I recieved a year or so ago from Keith Skjerdal. Thanks Keith.

Paul
 

Attachments

  • bulletstabilitycalc.xls
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I've had a couple of 1 in 12 twist .243 AI varmint rifles to shoot the 75 gr. V-max and Ballistic tip bullets. Worked extremly well for getting woodchucks out to 500-600 yards.
 
Ok....so then nobody here and who has fired an 87Vmax very accurately out to say 300-400 yards, has been able to fire a 75Vmax just as accurately out of the same barrel? If you have, then please mention the twist rate that best serves these two bullets.

And ....nobody here who has fired a 105Vmax accurately to say 300-400 yards, has been able to fire an 87Vmax accurately out of the same barrel? If you have, then please mention the twist rate that best serves these two bullets.

I'm thinking that a 1-9 might be best for the 87 and 105 Hornadys (?) And 1-10 best for 75-87 (?)

My thinking is that it seems the 1-8 is best for a 105, but too fast for the 87. But, then I'm worried that if I go with the 1-9, it may be satisfactory for the 75 (if even a little fast for it), but not quite fast enough for the 105 in extended distances.


pbike,
I've never used Excel. I entered the values in the boxes, but how do I get it to calculate?
 
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Van

When my 8 twist long range barrels are no longer competitive I use them for live varmint shooting. I shoot everything from a 71 grain Berger BT to the 105grain Berger VLD with minute of prairie dog accuracy. The two best bullets I have found are the 80 grain Blitz and the 87 grain V Max. In a 244 Ackley I can shoot them at 3500 and 3400 fps respectively, with ease. i don't think you'll find a better bullet than the 80 Blitz.

All of those stories about a twist being too fast should be taken with a grain of salt.

JMHO

Ray
 
Cheechako - do you know of a place that has any of the 71 bergers left?

Minute of PD means different things to different people. I insist on match grade accuracy, even if I will never use it that way. If it don't shoot, it gets redone until it does shoot. Been down that road, have the canceled checks to prove it.

Pick a bullet, build the rifle for it and you will be happier with it in the long run.

I have not had the good luck of having a rifle that will shoot every bullet weight to what I consider to be an acceptable level of accuracy.

There is no one twist fits all. Otherwise, there would be only one twist.

JMO
 
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Andrew

I've always gotten mine from Bruno's. What have you heard? Are they in short supply?

Ray
 
Berger stopped making them - not enough demand, plus they have the flat base 70's and 80's that are close.

They will make them for you if you buy 10,000.

I love the 71 BT - prints several inches higher at 300 yards over the same amount of powder then the flat base 70, shoots into a nickel at 300. Perfect bullet for the 6mmbr - in a 1-12 twist :)

70 Sierra blitz king is close, but not a berger.
 
Andrew

Sorry to hear that. I did not know. It's my 600 yard PPC bullet. I shoot it in a 12 twist at 3550 fps.

I saw your edit. When I say "minute of prairie dog" it's just a tongue in cheek expression. I'm a Benchrst shooter and am never satisfied with accuracy. But most of the bullets and loads that I've tried in my shot-out 8 twist barrels will shoot in the threes with an occasional two or one just to make it interesting.

Ray
 
Vani,

That Excel file gives you answers in 4 formats... what you want is the one in the lower right corner "minimum twist rate"

Fill in answers for the bullet length, diameter, weight, desired stability factor (1.3ish), and speed at muzzle. Each entry you make will recalculate the twist rate... watch as you go.

the other thing that should be mentioned is you won't find a twsit rate that works perfect for all the bullets you want to shoot. The fastest twist will stabilize the longest bullet, but it may "overstabilize" the shortest bullet. Some say there is no such thing as Over stable... I disagree! To have the best performance you don't want bullets coming apart on way to the target from spinning too much.., just as you don't want a rifle twisting violantly in the bag as you fire from a bullet twisting too much, hence the 18 twist 30 BR. If I were in your shoes I would have 2 barrels One for the longer heavier bullets, and one for the shorter lighter faster bullets.

Paul
 
Don't try to do it all

Another vote for sticking with one twist/bullet weight range and not trying to do it all. I'd pick a 12 twist and my first bullet selection for your specified range would be the 80 gr. Berger or Fowler.
 
Guys, I really appreciate your help. And Andrew, Ray, and Paul, the detail is very helpfull. Andrew, you are the 2nd or 3rd person to tell me that he couldn't get the 87's to shoot good in a 1-8 twist barrel, while the 105's worked great. I wonder if it's something about the barrel just not liking a Hornady 87Vmax, or is it possibly a matter of a 1-9 twist fixing that. I was delighted to see your 6x47 giving you velocities 3,050-3,100 FPS. I used a safe 2,900FPS to base all my calculations. And the actual higher numbers you report would give me that much better performance.

Gents, I really tried to print and explain as clearly as I could that I am not looking for a barrel to fire "all" bullet weights, but am looking to fire just TWO bullet weights.

I am really desiring to focus on the high .400BC 87Vmax. I intend to shoot this rifle at distances starting at 400 yards, and out to 600 yards or more. But, as you know it would be a mistake to build a rifle based exclusively just on the one bullet. Therefore, I would want another bullet with a high .500BC like the 105Amax.

I have found that a lot of folks who are trying to help me, don't realize that the true target bullets (ALL Berger 6mm bullets included) make for very poor PD or chuck performance with the wounded animal often scurrying back into the burrow. They commonly only pencil a hole through the animal. This is why I cannot consider any target bullet acept the 105Amax. The 105Amax is an exception being that it is the ONLY target bullet reported to expand moderately or violently in small varmints.

This is why you see a spread in my choice of the two bullet weights. If a 105Amax doesn't work, my next only available choice in a high BC is the 87Vmax. If my rifle doesn't like one of these bullets, then I can try the other.
My original choice was to consider a barrel that could fire the 87Vmax, and also accurately fire a .330BC 75Vmax. . The spread between these two bullet weights is much tighter, and it would probably be easier to choose a single barrel twist. But, at 500-600 yards the performance of the 75Vmax just doesn't compare.


So the question is: Will I find a single barrel twist to handle both the 87Vmax and the 105Amax? A 1-9 twist?
 
Call Hornaday

I guess the best answer would be to call Hornaday ,they are wonderful people and they will tell you the straight dope on the twist question.BTW I use their 75 and 87 gr vmaxs in my 6-284s with 12 twists,the 87 is very effective on varmits at long distances -800-1100 yds when driven at 3725 fps.the 75 while flatter at shorter distance 600 or less will run at 3885.these are my velocities at 1242 ft alt. 58deg. 85 % hum. bar.30.32
 
Roger T said:
I guess the best answer would be to call Hornaday ,they are wonderful people and they will tell you the straight dope on the twist question.BTW I use their 75 and 87 gr vmaxs in my 6-284s with 12 twists,the 87 is very effective on varmints at long distances -800-1100 yds when driven at 3725 fps, the 75 while flatter at shorter distance 600 or less will run at 3885.these are my velocities at 1242 ft alt. 58deg. 85 % hum. bar.30.32
Click to expand...

Roger,

I already did. I also called Berger and Nosler too.

I learned some helpful tips from Hornady and Berger. But, you still have to be carefull and double check what you are hearing.

Reps can be much better at answering non-mitigating black and white questions that have precise answers. The Hornady rep told me that the 105Amax is not designed or rated for varmint as it has a thicker jacket then the Vmax. So that is good "black & while" info to know. But, he also told me; "if a bullet is stabalized at 100 yards then it's going to be stabalized at 600 yards". That is incorrect, as you and I have both heard instances of keyholing and instability problems beyond the 100 and 200 yard targets.

And Eric at Berger told me to stay away from Berger .243 bullets as they are not designed for expansion.

So YES, reps can provide some good info, but you still need to do your own homework. This is where the hands on experience from VERY seasoned shooters like of those that I can find here, will trump over the opinion or input of one rep. Your particular experience with the 12 twist and those two bullets is valuable info that a rep may not know. The Hornady rep was telling me to go with a 10 twist for an 87gr down to 70gr bullets. Maybe the slower velocities from a smaller 6x47 case require more stabalization when compared to a hot 6-284.(?) But then too, maybe an 11 twist would be even better? Like I say, that was just one reps opinion.

Think I really like the 87 and 105 though.

PAUL,
Thanks for that EXCEL page. I was having a problem trying to use it yesterday because I failed to apply the decimal point on the caliber entry. I guess a bullet that is 243 inches wide (instead of .243") would throw the program off a bit. :D

Once I get the bullets arriving in the mail, I will refer to it to get a second opinion. But, the living and breathing experienced shooters loike you on this thread are who's opinions I weigh most.
 
You're confusing yourself.

The "just two bullet weights" you keep coming back to happen to sit in two different twist ranges in terms of optimum theoretical performance and that is where you go off track.

To shoot any bullet you need enough twist to stabilize it. You can be sure your 105s won't work in a 12 twist. I suspect that a 10 twist won't do it either. Others are writing that you should pick 8" for this bullet. You have to have enough twist so if you're going to use these 105 gr. bullets you don't have that many options. 8" is by general experience a good twist for that bullet. I wouldn't pick it because I don't think that bullet range is the best choice for your stated needs.

This statement is not correct:
"I have found that a lot of folks who are trying to help me, don't realize that the true target bullets (ALL Berger 6mm bullets included) make for very poor PD or chuck performance with the wounded animal often scurrying back into the burrow. They commonly only pencil a hole through the animal. This is why I cannot consider any target bullet acept the 105Amax. The 105Amax is an exception being that it is the ONLY target bullet reported to expand moderately or violently in small varmints."
Click to expand...

I've used the bullets I referred to, the 80 Berber and Fowler (which you term "pure target bullets") and they make chunky hamburger at the ranges and velocities you are writing about shooting. This is based on personal experience -- not something I read.

You have more bullet choices than you think. I suggest again that you ignore the 105 and go with the mid-weight bullets in a 12 twist. You're asking too much from one barrel.
 
VaniB,

A 12 twist is on the edge for an 87 Vmax. A 10 would be best. The 8 tw is good for 105, but cost you speed for the 87. I know guy with 1000 Kills on groundhogs with the 87 V max out of a 6mm Rem. I think the 87 Vmax is the best 6mm long range varmint made.

Good luck

Mark Schronce
 
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