Tight Neck or Not?

[kory]

Gentlemen,

I'm about to take the 6BR plunge, primarly for paper punching. Mostly 100 to 300 yards, but maybe as far as 600 yards. My action is a trued Savage Model 12 Single Shot.

My first question is what neck diameter should I go for? .262 or large enough so that I don't have to neck turn? I do have all of the neck turning tools as I do it for my 17 Mach IV and 6PPC, but if it really does not provide that much an improvement, I'm wondering if it is worth it.

Secondly, what twist should I get?

Any feedback you can give me would be great!

Thanks,
Kory

 

[kory]

Hi Corbin,

Thanks for the reply. You don't think an 8 twist is an over kill for < 600 yard shooting?

Regards,
Kory

 

[BountyHunter]

you will need the 8 twist for the heavier 100-108 gr bullets that will be needed for the 600 yard, particularily if you go with a straight Br and not the BRX or Dasher.

.272 neck is the way to go with Lapua brass and either Varget or N540 normally.

BH

 

[kory]

If I were to ask the same question again but say maximum range will be 300 yards, what twist would you guys recommend? The reason I ask is that I'm not ready for 600 yards yet, I still need to develop my skill in the 300 yard range. I wonder if it makes sense to get a barrel optimized for the closer range now and then later get one for longer range?

I've read the barrel FAQ several times and I'm still confused. For example, if 14 twist is supper accurate up to 200 yards, how can 8 twist, which is almost twist as fast, still be real accurate in that range?

Regards,
Kory

 

[Forum Boss]

I've read the barrel FAQ several times and I'm still confused. For example, if 14 twist is supper accurate up to 200 yards, how can 8 twist, which is almost twist as fast, still be real accurate in that range?

Because the long bullets are suprisingly accurate even at close range if you have a good barrel and chamber. My PacNor has done multiple 3-shot groups in the Ones at 100 yards with 105 Scenars, and Scott Parker's Broughton has shot in the high ones for five shots. So, while the short flat-based bullets SHOULD be more accurate at 100-200 you have to be a really really good shooter to shoot up to their potential,high zeros, low ones). With the 1:8 barrel and the long bullets you have a higher BC working for you.

For pure accuracy, you have to look at what the PPC BR guys are going. Currently, everybody is still using slow-twist barrels and short Flat-based bullets at 100-200. But at 300+ it is a whole new ballgame. If you shoot where it's windy, we'd consider going 1:8 even at 300. Or go 1:10 and shoot the 88s and 90s.

 

[cycbb486]

I am by no means any expert but I have a 10 twist in progress. My decision for this was the same in regards as not ready for the 600 or 1000 yds. I went with the 10 twist. This is my first custom job. My decision was based on a earlier article by Danny Reever and all the other articles and reports on the 6 BR. He wrote a article about how to make the 10 twist work. In his tests he found that the 10 twist using Berger 95gr VLD's seemed to perform better out to 600 yards versus a 8 twist and the 105's and 107's SMK. I thought what the hell and try it out, this combination should at least cover me out to 600 if I want to try it. As I said I am no world of knowledge but I am willing to give it a try. Read his article and give the 1-10 a try. The majority from what I have seen and heard say the beginner should go with the 1-8 because it is hard to make it not shoot. If one is willing to experiment why not try the 1-10?????? What's the worst it will cost? Another barrel and chambering job?


If I am out to lunch could someone please tell me so!!!!!!!


Calvin

 

[Forum Boss]

Calvin,

Bearing in mind Danny's work, Henry Childs has done subsequent work with the 95 VLD, and I just talked to Berger last week. By all appearances, you will need about a 1:9.3 or so to stabilize those 95s. It appears the twist on Danny's barrel was actually faster than spec'd by the barrel maker. That said, if you can push them faster, that equals more rpm. But, according to Henry, you'll need a 1:9 to stabilize those 95 VLDs at around 2800 fps or at low ambient temperatures. On the other hand, there is a wide range of 80-90gr bullets that should work very well with the 1:10. If your 1:10 is closer to a 1:9.5 you may be in luck. Plus with the right powder choice and enough barrel length, we think you may be able to push to 95s to around 3000+ fps, maybe as fast as 3100 with a 29" tube. If your barrel hasn't been completed yet and you really want to be safe, consider going with a 1:9.

But remember that bullet stabilization is,generally speaking) a function of how fast a bullet is spinning. And the amount of spin is determined not by just the twist rate, but by the twist rate AND the speed with which the bullet moves through the bore.

We did some rough calculations, and it appears that a bullet moving 3050 fps from a 1:10" twist 28" barrel should be spinning 98% as fast as a bullet moving 2800 fps from a 1:9" twist 28" barrel.

Get that 95gr VLD moving quickly enough and you may be in business. We note that Henry believes strongly that a 1:9 twist in minimal for the 95gr Berger and that a 1:8 twist is better.

We've been talking to Berger and we may try to do a definitive 1:10 test to see the minimum muzzle velocity needed to stabilize that bullet. Berger believes the bullet will stabilize in a 1:10 if they are driven fast enough. Just how fast is the question...

Here is a basic formula you can use for calculating RPMS

,velocity in fps) X 720
----------------------- = spin in RPM
twist in inches

 

[Aussie_bob]

Well the way around that then in a 1 in 10 is to chamber 6BRX and fire form your brass that extra 0.10 get the extra few grains of powder in and the 1-10 will stick with the best of them.
I am having built here in Australia a 30Br and when it is finished i will also be getting a 6mm barrel for it and chambering in 6BRX and i am also looking at a 1-10 barrel and using Berger 95grVLD so if you are not successfull in getting it to shoot i could go the 1-9.5 but by all accounts 1-10 should be fine.

 

[shcal]

Gentlemen: I have been reading a lot about the 6BR here and many people have had questions about barrel length, twist rate, weight of bullet and whether to go with a 6BR, Dash, BRX etc. Well her goes another one of those questions. First let me describe what I shoot - most of the time ground squirrels here in California. It is usually very windy and I have never had a shot less than 100 yds. Most shots are in the 200yds to 500 yds range. I just discovered my local range has a 500 meter club and I am thinking about joining that group for some 500 meter competitions. OK, the big question should I go with a 6BR, Dash, or BRX? 30 inch barrel? No turn neck? 1:10 twist or 1:8 twist? will probably shoot varmint bullets,Hornady v-max 87 gr, Burgers etc.) and match bullets. All and any suggestions are welcomed and I thank you in advance.

shcal

 

[Forum Boss]

The std 6BR, BRX, and Dasher are ALL good options. The only thing we'd definitely suggest is to go with a 1:8 so you can shoot the 105-107gr bullets at 500 when its windy.

We are getting good Vs with a standard case, but running the pressures pretty high. You can get somewhat higher Vs with Dasher or BRX, but then you sacrifice neck length--there is no free lunch. The Dasher requires custom dies. But Redding makes them, and for a seater you can just have your smith ream the sliding sleeve in the Comp seater die, which shouldn't be that expensive. So all you really need is a FL Type-S die.

As to the turn vs. no-turn question, most people seem to favor no-turn. But turning cases isn't really that big a deal IF you already have the tools and IF you're not making 200+ cases. For an active ground squirrel shooter, we'd want two rifles--a 22 Mag or 17 HMR out to 200 and then a 6BR or 22BR for longer distances. The no-turn will make it easier to get the volume of cases you'd probably want to have. You could even load these up on a progressive with a spherical powder like BLC2 that meters consistently. Varget and IMR4895 don't agree with most progressive powder measures.

Back to the Dasher vs. Std question. If you're sure you want to shoot nothing heavier than the 95gr Berger, we'd do a 28" 1:9 twist bbl with a standard case. If you want to shoot the heavier bullets, then you'll NEED a 1:8 and the BRX/Dasher becomes much more appealing.

 

[shcal]

Moderator:

Thank you again for your thoughts and insights into the 6BR/Dasher/BRX question. I agree with you, there is no free lunch and there is really no one answer. However, for my shooting,and by the way, I do own a 17HMR, a 22-250 AI and a 6PPC)I think I would like to go with either the 1:8 twist,to keep my options open) in either the 6BR,to make reloading Faster/Easier) or the Dasher,for the extra Velocity/Distance). Oh decisions! Well, when I make up my mind I'll let you know. As for barrel length, 28" in BR and 30" in Dasher?

Thanks again.

 

[James EPS]

12 twist 6BR gets my vote, I can shoot 68gr at 100yrds, 74gr at 200yrds and 80grs out to 600yrds. I got a 26" 3 groove Pac-nor barrel which shoots great its a large shank 1.120 no taper super match stainless for my Savage.

James

 

[CGSteve]

Tinman,
What are the chamber dimensions on your Pac-Nor barrel? I've got an order in with them right now for a 6BR, 11T, 3GR, 1.055 straight tube.

Thanks,
Steve

 

[LeeinOH]

Pac-Nor is going to be very busy with 6 BR's. I just ordered a 1.120" no taper 28" long 8t 3g in 6 BR with the .262" neck. Going to have it throated for the 105 VLD

 

[Dave]

I am using 90gr Lapua Scenars for 300m ISSF. My twist is 1:8 but Lapua advise that 1:10 is their ideal for the 90gr. I did as a matter of interest try 95 Bergers in my 1:10 .243W and they didn't stabilize,3 foot group). My neck is standard,.270) and is close to being a fitted neck for non-turned cases. Lapua brass is so good that neck-turning is not worth the effort. Using Wilson dies, my seating tension displays no discernable difference in a batch of 100 rounds. When I do my bit I can occasionally group 10 shots under 2" at 300m,sling and peep). Ten.

 

[Rust]

Fer crying out loud. I went the 1-10 twist route with a 6mm Rem Ackley improved and even with a 27" barrle and high velocities it didn't want to consistantly stabilize the 95 gr Lapua Scenars. Waste of a decent barrel, shoots lighter stuff pretty well but it didn't achieve it's intended purpose so it was a failure.

For 95 grain stuff go 1-9 and don't run the risk of wasting a barrel and your money. No, the 1-9 won't ptoperly stabilize the 105/107/108s. For bullets in the 105 range just go 1-8. Period.

But if you're going to build a 6BR you might as well just do it in 1-8. It isn't any more expensive to load and shoot the 105s, and depending on barrel length it will get you out to 1000 and still light things up at 100. Maximum versatilty unless you plan on having multiple barrels to switch of course.