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View Full Version : What twist for 30BR



rputansu
08-28-2008, 01:10 AM
I am in the planning stages of putting together a 30BR LV and would like to hear what twist and why? What pills to push and popular weights? The usual load data, popular powders and why the choice. This will be my first full out BR rifle and I want to sift through the information so I can make an informed decision. I have several accurate varmint rifles (223, 257Rbts, 6BR, 308) and think it's time to commit to a purebred benchrest rifle.
TIA for the input,
Robert

mturner
08-28-2008, 01:20 AM
I have found that an 18" twist is great for 110 gr to 125 gr bullets. You can even do fine with the 135 gr. Some may think this is pushing it a bit, but if they ran the test I did, I believe they would agree. I fired a group with the 150 gr Sierra Matchking from a 18.7" twist. I was very surprised to see that they went into .170". I would never push it this far in a match. The same bullet in a 20" twist resulted in tumbling bullets. Stick with the 125 gr and under, because this was from my 30-30, and the velocity of the 150 gr was 2800 fps. The new 115 gr Berger with a dose of H4198SC would be a hard combination to improve on.

Michael

Dick Grosbier
08-28-2008, 06:56 AM
17 to 18 Twist, and if this is to be a LV light bullets such as 112 Bibs , 110 Bergers, or 115 Eubers to name a few will be easier on the shoulder. H4198 is your best all around powder choice , N130 is also very popular but more expensive and frequently harder to come by.

Dick

MRL
08-28-2008, 07:56 PM
If this is your first BR rifle seriously consider not building a 10.5# LV 30BR. I did it and found the recoil was annoying to say the least, a 13.5# 30BR will be easier to learn to shoot well in a shorter time frame.

jackie schmidt
08-28-2008, 08:10 PM
Just like the 6PPC, there is now an entire industry that has cropped up in support of the 30BR.

A typical 30BR rig will have a 1-17 or 1-18 twist barrel, shoot 112 to 125 grn bullets, use N130 or H4198 powder, have a "zero" freebore chamber, and probably be built on a HV platform.

This wheel has been invented, and invented quite well. You mentioned "pure bred Benchrest Rifle", I assume you are going to shoot score. For group, I would still go with a 6PPC.

I agree with MRL in that unless you are going to be competing in a lot of IBS Varmint for Score matches where they do shoot LV in quest for Shooter of the Year Points, build a HV. While many will tell you that a 30BR at 10.5 pounds is no problem, it does pop you pretty hard, especially if you shoot free re-coil.......jackie

eww1350
08-28-2008, 08:22 PM
I wouldn't waste time building a 30BR...Jim Borden has one for sale in the classifieds for $2300...that is a bargain...this rifle is built on the Rimrock BRM action...these rifles he builds shoot 250-25x pretty often and you can have it NOW...
just my 2 cents worth...

rputansu
08-28-2008, 10:26 PM
Well,
Some sound advice. I'll go with the HV platform and the longer twist of 17 to 18. Getting beat up at the bench isn't appealing. I must admit that I don't quite understand why the 17 or 18 twist shoots better than say a 13 or 14 in the 30 cal. I have a 14 twist 6BR that shoots the light pills very well but why does the 115 grain or so 30 cal pill shoot so well in a 17 or 18 twist? I just can't wrap my mind around it.
Also wondering if anyone has tried Varget in the 30BR. I must admit I have a fondness for Varget because it is so forgiving in many caliber combinations.
Thanks for the replys,
Robert

Mike Swartz
08-28-2008, 10:41 PM
Robert;
Varget is slow for a .30BR. The reason that the .30BR requires a faster powder is the difference in the expansion ratios of the cases when compared to a 6BR. However, you owe it to yourself to try Varget in your rifle when you get it and prove this to your self. The reason for the slow twist barrels is the reduction in torque at load start. I don't see any reason that a .30BR would shoot worse with a 14 twist barrel other than the jumping around in the bags that comes with a faster twist. I saw a .30BR built on a 10 twist barrel when they first came around. The rifle was a bear. I would like to try a Bartlein 22 to 16-17 gain twist barrel with a .30BR. It might be even more calm. We'll see.

Mike Swartz

jackie schmidt
08-28-2008, 10:43 PM
Varget is on the slow side for the 30BR with the lighter bullets.

The reason shooters use the slower twist is because it is deadly accurate and really tames the Rifle down in the bags, ie, very little torque. You can really tell the difference when going from a 14 or 15 to a 17 or 18.

Randy Robinette of BIB bullets can give the best explanation as to why the faster powders work so well in what is a relativew small case for such a large caliber.

This is one of those instances where a lot of good shooters have already done a tremendous amount of homework geeting this combination to work. Don't be tempted to re-invent this wheel.......jackie

eww1350
08-28-2008, 10:44 PM
Robert, the caliber of the bore and bullet weight determine barrel twist..Most of the super slow twist barrels used today were direct results of trial and error testing NOT from a ballistics chart..Varget is a slow burning powder that requires a specific bore diameter to bullet weight ratio to work properly..
The 30BR has had every powder in the book tested for best fit..and when you hear H4198 or VV N130 is a good fit..then save money and bullets..you won't beat that combination...Your biggest challenge is going to be learning good consistant bench technique behind the 30BR..Buy a bunch of good custom 112-118 grain bullets and a lot of H-4198 and practice with windflags as often as possible..The great thing about a 30BR is one barrel will last 5 times longer than any 6mm ...
I have both 17 and 18 twist rifles, and both shoot equally well...When I beat the 6ppc's in a group match, I can't stop smiling for a week..:D:D

rputansu
08-28-2008, 11:12 PM
Excellant,
I never thought about the resistance, makes perfect sense. I agree with not re-inventing the wheel. I will take the advice and spend the money on good bullets and powder. One of the things that swayed me towards the 30BR is barrel life. I like the idea of building confidence in your equipment and knowing that you'll have it for a while before the accuracy begins to slip.
Robert

Al Nyhus
08-28-2008, 11:24 PM
Robert, the caliber of the bore and bullet weight determine barrel twist

Bullet length, not weight, is the important thing.


Most of the super slow twist barrels used today were direct results of trial and error testing NOT from a ballistics chart.

The 'slow' twist .30 cal. barrels resulted directly from Randy Robinett's work with the JBM Ballistics Drag/Twist Function program. The JBM calculations are based on the works of the late Robert McCoy (McDrag, McGyro, etc.) Randy spoke to this directly in an article I wrote for Precision Shooting several years ago where he detailed the development of the so-called 'slow twist'* barrels and the 30BR cartridge.

* - A 6PPC with a 1:14 twist barrel shooting a 65-68gr. bullet based on a .825 length jacket at around 3,400 fps.(the 'normal' 6PPC combo) has a G.S. (Gyroscopic Stability) figure of around 1.4.
- A 30BR with a 1:18 twist barrel shooting a 118-125gr. bullet based on a 1.00 long jacket at around 3,000 fps. also has a G.S. number of around 1.4.

So...why are the 17-18 twist .30 barrels considered 'slow twist'? :confused: They are no 'slower' with respect to the G.S. number as the thousands of 1:14 barrels that have been chambered for the 6PPC's over the years.:rolleyes:

Even after all the seasons of these .30's being proven competitive, you still get shooters that can't imagine how a 'slow twist' .30 can work....when in fact they're shooting the identical combination on their 6PPCs. ;)

Al Nyhus
08-28-2008, 11:35 PM
Randy Robinette of BIB bullets can give the best explanation as to why the faster powders work so well in what is a relativew small case for such a large caliber.

Another attribute is the reduction in muzzle pressure from using these faster powders. The 30BR (and probably the 30PPC as well) have expansion ratios that make some of these faster powders behave quite differently from what most would suspect. -Al

Pete Wass
08-28-2008, 11:52 PM
That so many people consider a 30 BR as a high recoiling rifle. Lots of us shoot larger cased 30's in 10 LB rifles with 2.25" forends free recoil all day long. Some of even shoot two of them all day long, without any adverse effects ; as far as we can tell! That considered, a 30 BR in a LV configuration shouldn't be a a big deal, especially if one puts a small Sorbathane pad on it. Heck, you'd never feel it go off, hardly!

caroby
08-28-2008, 11:55 PM
Robert, the caliber of the bore and bullet weight determine barrel twist..Most of the super slow twist barrels used today were direct results of trial and error testing NOT from a ballistics chart..Varget is a slow burning powder that requires a specific bore diameter to bullet weight ratio to work properly..
The 30BR has had every powder in the book tested for best fit..and when you hear H4198 or VV N130 is a good fit..then save money and bullets..you won't beat that combination...Your biggest challenge is going to be learning good consistant bench technique behind the 30BR..Buy a bunch of good custom 112-118 grain bullets and a lot of H-4198 and practice with windflags as often as possible..The great thing about a 30BR is one barrel will last 5 times longer than any 6mm ...
I have both 17 and 18 twist rifles, and both shoot equally well...When I beat the 6ppc's in a group match, I can't stop smiling for a week..:D:D


Robert......

I promise you that your getting EXCELLENT advice here!

You have chosen a WONDERFUL Benchrest cartridge....

My .02 worth of advice...
The rifle, yes build one that'll weigh 13.5 finished... But one that can be a 10.5 with just barrel/weight system swap.
Bolt face, get a .308 bolt face >>> That will "pick out" a .440 PPC rim<<< as well... ANY of the custom action makers can do this set-up with ease...

Barrel, If a cut barrel Krieger, Bartlein, Rock Creek, Brux... Then you'll get an exact twist rate............... Button rifled Hart, Shilen, PacNor, Broughton, etc ... It may be advisable to go the 17 twist so you know your OK "if" the barrel measures 17 1/2" or 18" twist rate finished.... The button barrels "can" slip in the twist rate a tad... Safe to go one inch faster in the twist rate...

Good news..... The .30 barrels of today are FREAK'N Awesome!!!! I'll bet you'll get a SHOOTER... The SHOOTERS are by far THE NORM!

Bullets.... These to SHOOT.........AMAZINGLY well! BIB'S and Cheeks are outstanding.

Powder............... H4198 <<<< Ohhhhh Yesssss.!
Bet you'll see LOTTSA virtical out of Varget....Way to slow...


Here is the big thing I have learned about the 30BR.... Pretty stout neck tention...Example: I shoot a .334NK and my finished rounds (bullet seated in neck) measure .3323.... I use a .328 bushing to achieve .004 neck tension.
anything less and some degree of virtical you'll get or "fatish" groups....

Good luck on your set-up.... You'll see, Absolute FUN!

More advice will follow in this thread....

cale

alinwa
08-29-2008, 01:54 AM
Well,
Some sound advice. I'll go with the HV platform and the longer twist of 17 to 18. Getting beat up at the bench isn't appealing. I must admit that I don't quite understand why the 17 or 18 twist shoots better than say a 13 or 14 in the 30 cal. I have a 14 twist 6BR that shoots the light pills very well but why does the 115 grain or so 30 cal pill shoot so well in a 17 or 18 twist? I just can't wrap my mind around it.
Also wondering if anyone has tried Varget in the 30BR. I must admit I have a fondness for Varget because it is so forgiving in many caliber combinations.
Thanks for the replys,
Robert


Maybe I missed it but I haven't seen this mentioned.

You ask this question, "but why does the 115 grain or so 30 cal pill shoot so well in a 17 or 18 twist? I just can't wrap my mind around it."

Here's one reason that will make sense.


One of the biggest contributors to dispersion on the target (group size) is something called "bullet eccentricity", the fact that no bullet is PERFECTLY balanced means that they all wobble some, their center of rotation isn't perfectly matched to center of form.......... in other words they're heavier on one side.

The slower you spin a bullet the better for accuracy, AS LONG AS you don't sacrifice stability.

If you were to shoot the same bullet from an 18" twist and a 10" twist barrel then it follows that the bullet which is wobbling LESS will show less dispersion (tighter groups) This is a wonderful thing :) with the thirty-cal's you get very well balanced bullets, a setup that's as inherently accurate as the 6BR, a setup that's just as stable ballistically as the 6BR, AND the added bonus of a slower rotation on your projectile......... it's a win-win.


Except for the recoil.



Now, to diverge a little.

Let me point out that if you run that BR reamer in a little deeper and use the 30X47 for your chambering you will not only be able to make just as good a shooter, but you'll also have a legal HBR gun. You could conceivably shoot this same gun for Group, Score AND Hunter Bench Rest. THIS would make it a purebred BR rifle. I'd put it together to make 10lb with a 6X scope and with a weight system to bring it up to 13.5 when you want to. I'd furthermore make a 3" wide removable plate for the forend for score and group shooting...... I have one of these setups and with it can compete in literally any venue.


If you can handle the recoil.

I can't see a downside to the 30X47 based on the new 6.5X47L case.

UN-believably accurate.

UN-believably wide tuning windows.

BTW the Borden is a good deal.


al

Al Nyhus
08-29-2008, 05:58 AM
One of the biggest contributors to dispersion on the target (group size) is something called "bullet eccentricity", the fact that no bullet is PERFECTLY balanced means that they all wobble some, their center of rotation isn't perfectly matched to center of form.......... in other words they're heavier on one side.

The slower you spin a bullet the better for accuracy, AS LONG AS you don't sacrifice stability.

If you were to shoot the same bullet from an 18" twist and a 10" twist barrel then it follows that the bullet which is wobbling LESS will show less dispersion (tighter groups) This is a wonderful thing :) with the thirty-cal's you get very well balanced bullets, a setup that's as inherently accurate as the 6BR, a setup that's just as stable ballistically as the 6BR, AND the added bonus of a slower rotation on your projectile......... it's a win-win.al

alinwa: Let's take this a bit further.

-You have 6mm and .30 cal. jackets.
-Both have a T.I.R. of .0002.

Which has the potential to produce a better bullet? Think 'circumference'. :)

alinwa
08-29-2008, 12:40 PM
Al,

Exactly ;)

al

mturner
08-29-2008, 01:00 PM
Most people on here have realized the accuracy advantages of using as slow a twist as you can get by with and still stabilize the bullet. Here is another big advantage. Let's take a 150 gr bullet at 3200 fps and you will have a bullet rpm of 230400. Now the same bullet out of a 16" twist will have an rpm of 144000. That's 86400 lets rpm. This drastically changes the bullets ability to penetrate to the vitals of game. So you hunters need to try this. I was actually a little disapointed in how the Ballistic Tips don't expand as much on neck shots on deer. It used to bore a 3" hole through the neck with a 10" twist, but with a 16" twist it's more like 1.5" hole. Now rather than using 180-200 gr bullets with a 10" twist in my 30-338 Win Mag for Elk hunting, I will be using 150 gr pills and a 16" twist with equal penetration.

Michael

rputansu
08-30-2008, 12:26 AM
Alinwa brings up a curious point with the 30X47. This seems to be a versatile cartridge but how much of a hastle would it be to switch from group, score and HBR? Money always seems to be an issue so I will most likely stick to single purpose rifle for a while. I will have to take a look at the 6.5X47 and compare it to the BR case.
Is there an advantage of 30X47 over the 30BR?
Robert

alinwa
08-30-2008, 02:38 AM
Alinwa brings up a curious point with the 30X47. This seems to be a versatile cartridge but how much of a hastle would it be to switch from group, score and HBR? Money always seems to be an issue so I will most likely stick to single purpose rifle for a while. I will have to take a look at the 6.5X47 and compare it to the BR case.
Is there an advantage of 30X47 over the 30BR?
Robert


The advantage of the 30X47 is that it's legal for Hunter Bench Rest where the 30BR is not. The 30BR is responsible for a resurgence of Varmint For Score Shooting and for the decline of Hunter Bench Rest.

In my short experience with the 30X47 I find it to be equally amenable and as accurate as the 30BR.


The switch is accomplished by bolting/unbolting the aluminum forend plate and by changing out the scope. YES it's a bit of a hassle but you're actually competitive with ONE rifle.

HBR= 10lb rifle, 30cal case w/45gr H2O capacity and limited to 6X scope (or taped down variable) with a 2 1/4" wide forend. This is your "base rifle.

VFS= 10.5 or 13.3lb rifle, any case/cal, any scope power. 3" wide forend permitted. For these disciplies you bolt on your forend plate and add weight as desired into the buttstock. Upgrade your scope power.

Group= 10.5 or 13.5lb rifle, any case/cal, any scope power. 3" wide forend permitted. For these disciplines you bolt on your forend plate and add weight into the buttstock as desired. Upgrade your scope power.


hth


al

Dick Grosbier
08-30-2008, 06:37 AM
The 30BR is responsible for a resurgence of Varmint For Score Shooting and for the decline of Hunter Bench Rest.


I think you give the 30 BR way more credit than it is due when you claim it has caused the decline of Hunter Class shooting, there is no VFS to go to in NBRSA and in IBS the 3O BR is the cartridge of choice in Varmint Hunter class.

The decline of Hunter class is due to other Factors.

LHSmith
08-30-2008, 07:43 AM
............The "hunter" classes of both organizations require at the very least a magazine cut-out in the bottom of the receiver.

Some claim this compromises rigidity and therefore........... accuracy.

You don't say if you actually intend to shoot competition.......If you do my advice is to hook up with someone doing so and perhaps you can actually shoot the guns of the various disciplines.

As simple as it may seem, the various classes are difficult for laymen to grasp.

I recently had 2 rifles chambered to 30 BR and have started to shoot both VFS and Varmint Hunter at most matches, because I really enjoy both disciplines.

I have noticed a trend toward shooting 2-guns ( different classes) at score matches and it is good to see the hunter classes may not be on the verge of extinction.

FWIW...My Rem. 700 10# VH in 30 BR is at MY threshold of recoil tolerance...............I did consider the larger cases for Hunter class, but am glad I didn't go there......................Remember in competition you will shoot around 50 rounds/event...............and every one of those shots have to be let off EXACTLY the same----------Extremely difficult do .

jackie schmidt
08-30-2008, 08:37 AM
It has been a while since we got into the "why nobody wants to shoot HBR", but in the Gulf Coast Region, you could use your fingers and toes to count the number of active HBR shooters and still have one shoe on.

I know a lot of shooters who are wanting to build 30BR's and 30PPC''s, but none are interested in building a legal HBR Rifle........jackie

Al Nyhus
08-30-2008, 09:03 AM
The IBS and NBRSA Hunter classes mandate a smaller barrel profile than the Varmint classes. Additionally, the recievers cannot be wider than 1.400 and must have a cutout for a follower in them. The popular Panda and Viper actions used in the Varmint classes are 1.500 wide.

In contemplating building a (10.5 lb) 30BR...which is technically a Sporter class gun since the bore is bigger than .230...an NBRSA Hunter barrel profile will give the rifle a better balance than the normal LV profile. I've built 10.5 lb. 30BR's both ways and the balance issue is huge. A nose heavy 10.5 lb. 30BR in a 3" fore end stock can be an evil thing.

A HV (13.5 lb) 30BR using a LV barrel of no more than 22" length with the weight properly distributed in the stock (not always hung in the butt) is an absolute joy to shoot.

You can also get these 13.5 lb. HV's nose heavy with a HV barrel around 24" long and a very light stock...then aggravate the entire deal further by hanging a 36 oz. scope (think NiteForce) 3" above the bore. With that much weight that far above the bore on a nose heavy combination...when the rifle torques in recoil the weight being higher aggravates an already bad situation. You've effectively made the 'lever' longer that wants to twist the rifle out of the bags.

A well balanced 10.5 lb'er will go around a Score target a whole lot better than a nose heavy 13.5 lb. gun.

A nose heavy rig will almost always shoot good groups..but a Score rig is about going around a target with no change in the P.O.I. from the sighter to every record target.

Just my 2 cents worth. You can probably even get change back. ;) -Al

Dick Grosbier
08-30-2008, 12:06 PM
It has been a while since we got into the "why nobody wants to shoot HBR", but in the Gulf Coast Region, you could use your fingers and toes to count the number of active HBR shooters and still have one shoe on.

I know a lot of shooters who are wanting to build 30BR's and 30PPC''s, but none are interested in building a legal HBR Rifle........jackie

Hey Jackie
You are Right it is somewhat unfortunate but there's very little activity in the Hunter classes down south, it seems to be more a NorthWest, MidWest, and Western thing.

Dick

mwezell
08-30-2008, 01:34 PM
Why not just drop the case capacity rule in HBR and combine varmint hunter and HBR?:D

Flame suit "ON"-----Mike Ezell

jackie schmidt
08-30-2008, 03:05 PM
As the HBR class evolved over the years, certain things were dropped, such as safeties, functioning magazines, the ban on "target sights", etc. But, there are two features that now define the class, and are carved in Granite. They are the minimum case capacity, and the 6x scope........jackie

Con Cross
08-30-2008, 05:14 PM
Most people on here have realized the accuracy advantages of using as slow a twist as you can get by with and still stabilize the bullet. Here is another big advantage. Let's take a 150 gr bullet at 3200 fps and you will have a bullet rpm of 230400. Now the same bullet out of a 16" twist will have an rpm of 144000. That's 86400 lets rpm. This drastically changes the bullets ability to penetrate to the vitals of game. So you hunters need to try this. I was actually a little disapointed in how the Ballistic Tips don't expand as much on neck shots on deer. It used to bore a 3" hole through the neck with a 10" twist, but with a 16" twist it's more like 1.5" hole. Now rather than using 180-200 gr bullets with a 10" twist in my 30-338 Win Mag for Elk hunting, I will be using 150 gr pills and a 16" twist with equal penetration.

Michael


Mr. Michael Turner, do you really believe, that your out of place useless piece of information has a chance to be voted as the most important post on the BR forum?

Con

Al Nyhus
08-30-2008, 06:18 PM
I'm an advocate of both the IBS and NBRSA dropping the case capacity requirements for Hunter class.

In the IBS world, this would give us one 6 Power class. IBS's Varmint Hunter is identical to Hunter with the exception of having no case capacity minimum.

In the both organizations, I believe the elimination of the case capacity rule may possibly bring more competitors to the game. The 30BR road is pretty well mapped out and this would eliminate all the hassles of case forming, reamers, dies, etc. for shooters contemplating the buiding of a Hunter rig.

For me, the two defining factors in Hunter are the 6 power scope and the 2.25" fore end.

In fact, given a hypothetical choice to shoot 100 yds. with either a 6 power scope and a 3" fore end...or a 36X scope and a 2.25" fore end...I'd opt the former.

Now at 200 yds, my choice would be just the opposite. -Al

rputansu
08-31-2008, 12:21 AM
I may be asking what is obvious to others but where can I find the rules and regulations for all of the BR venues?
Thanks for all the great comments, suggestions and personal experiences.
Robert

jackie schmidt
08-31-2008, 12:25 AM
Go back to the home page. Look on the right, and you will see both the NBRSA and IBS logo. Just click on these, and the info on the sites will take you to the rule books..........jackie