6 mm BRX - what freebore and neck should I use?

Now Al,
I think that you could explain that when you are talking about tight and loose brass for fire forming that you mean headspace, as opposed to say the diameter at the back of the chamber, where, if I remember correctly, your reamer dimensions are uniquely generous, to avoid "click" and so that you can visually sort for case thickness runout.

On the subject of neck clearance, I know of shooters that go very tight. On the other hand, the fellow that may own the current five shot 100 and 200 yd. unlimited aggregates, told me that he strives for around two and three quarters thousandths. and another well known record holder said that he uses "somewhere between two and three" on the theory that it gives a cleaner bullet release. There are a couple of other well known shooters that have discovered that close is good, closer may not be better. It is an experiment that is on my list. There are some thinner cases in my range box, and a smaller bushing in my die.


Boyd
 
Al,
Loose is a relative term for both of us and we should probably define what we call that before we "disagree" cause we might be talking about the same things. But, for me, I call loose when the case has several thou of room in the chamber at several spots. Usually in the body. I'll use My WSM's as an example, (though they were almost all different from one another, perhaps as many as 15 different chamberings and dies made). All these were similar enough to look like a regular WSM, and mine were intentionally smaller at the base so as to keep primer pockets tight for the long run. Mine were also tigher at the shoulder. My cases would end up with about a grain or so less volume than most other peoples WSMs. But, even still, my unfired brass had less volume than a fired case has, and it's again, a grain or two. Other peoples ammo wont go in my guns, but mine will go in theirs. And the dimensions are close enough that I bet 15 or 20 different people use my WSM dies. (thinking back, I don't think i ever sold a set... lol).

Loose to me is about .002 around the lower body, maybe .005 at or just below the shoulder, length I think everyone gets reasonably close, but even there it might be .005 or so, and so on and so on. I bet most WSM reamers cut a body that goes from .540 or so up to .555 or .556. Stock spec is like .5586 at the base. That's pretty big. Most new wsm brass is around .550 or smaller. In a BR, (x, dasher, or whatever other variant), the dimensions may be somewhat closer, but I've purchased Norma BR brass and had different lots of it come in .003 different in dia. How? I consider that a lot in BR brass.

I remember that one area my cases were pretty close was on the shoulder flat. So close in fact, that if I neck turned with my K&M turner, the little burr that raised up on the shoulder when I cut that radius was enough to not allow a piece of new brass to go in the gun without going back in the FL die first. And that was not some gigantic burr either. It was so small it tricked me a few times at the firing line. (finding out then that my cases would not go in). Who'da'thunk you could not put new brass in the gun and yet it would gain volume 1.5gns after firing. :confused:

The moral of all our stories really is that freebore, necks, and about all other things to do with any case, are really best figured out by an individual with their own reloading processes. Almost everyone in this thread has a different story to tell. And, probably all are correct, in that persons own situation. It's for those reasons that there isn't always a "best way". We should say there are many "good ways". You for instance would have no interest in a no turn BRx. Someone else obviously would.
 
4Mesh
Phil a while back you posted some pictures of your case necks and Alinwa probaly missed seeing them.Any chance you can post that picture again?
Waterboy aka Lynn
 
Gun related pics are not stuff I generally keep Lynn. If it isn't something interesting to me, I probably posted it and then ditched the pic off my system. If it's not on the web, then it's gone. I shot a lot of macro pics of my ammo and other peoples. Some might still be on the PA club site, but not my ammo cause mine isn't clean and shiny like the Springmans stuff! hehe, I used Eric and Wes's for examples that looked nice AND shot! :D
 
Boyd and Phil,

I stand corrected........ yes by "loose" I most certainly was referring only to headspace. It is my opinion that brass MUST be jammed for headspace on fireforming. Side dimensions can be whatever floats your boat. BTW Lynn, Jim Borden taught me this, it isn't "my idea."

Phil, I'd really like you to explain the logic, the mechanics behind keeping the butt small to avoid sphincter enlargement..... Some really big-time shooters/builders buy into this notion and I just can't get behind it. I've tried tight chambers and tight boltfaces both and found nothing but grief. And in my experiments using chambers cut in increasingly larger increments clear out to .009 over I simply cannot see any evidence of "containment" nor any evidence that a casehead can spring back. It is my opinion, formed from wrecking a lot of cases, that caseheads cannot be contained.

The only form of control I ascribe to is "seasoning" or work hardening of the brass, including the casehead.

I once polished out a too tight chamber in increasing increments and was able to load hotter and hotter as it got bigger. Same everything else. It took a lot of work but the difference between .002 over at the base and .005 over at the base was significant. And IS significant, since I've gone to fat butted chambers I routinely run hotter than others and reap the benefits not from velocity gain per se but from easier cleaning and lower ES numbers.

al
 
Al, for the most part, I think primer pocket life is made or broke right at the first firing. In 1Kbr, many guys, including myself, like to shoot our fireform groups in a match. That means we have to run the load that "we run". No light loads for fireforming. If I shoot my regular load in a chamber that is bigger, I can pretty much write off the primer pocket on the first firing. In my tighter chamber, they have no problem with that first firing. At least as long as I don't go overboard with the load anyhow.

My brother made a die for closing primer pockets back up, and it really works nice. I have often wanted to try that with brand new brass to make the first work hardening in the direction of smaller, vs larger. Maybe then the brass would tend to spring back to the smaller dimension rather than always wanting to go larger.

I don't know if the smaller chamber continues to help as the brass gets older, I think it does. But I'm convinced it helps when it's young and matters the most.

It is official. We have digressed so far off topic now there is little left to say about freebore and necks! This should be in its own thread really.

I'm very surprised at your findings with the larger base'd chamber. Hmmm
 
Boyd Allen
Just to show you you the true charactor of that other poster please go to the 6mmbr website and look at Robert Whitley's article on the new Lapua brass.You will want to pay close attention to the dates on his posts there and my posts from several days prior on the Blue Box Lapua brass on this thread.I am guessing coincidence what do you think?
Waterboy

P.S. Here is part of his post and the date is shown.
July 23rd, 2010
Report: Thinner Neck-Walls on Latest Lapua 6mmBR Brass
Robert Whitley sampled a recent lot of Lapua 6mmBR brass and found that the neck-walls are marginally thinner, resulting in a very slightly smaller loaded neck diameter. Here is Robert’s report….

For the last few years the different boxes of Lapua 6mmBR Norma brass I have purchased (four different lots) have yielded brass with necks that measured around .269″ – .2695″ loaded. While this worked out very well in a variety of applications, sometimes I had to neck-turn that brass because it was a little too tight for an application or chamber I had. I recently received some of the latest “blue box” Lapua 6mm BR Norma brass (Lot # P00487801) and this latest lot of 6BR brass measures right around .268″ loaded (with popular 6mm bullet types
 
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Charles E said:
The best two choices you can make are (1) what bullets do you want to use, and (2) who's going to grind your reamer.

As for (2): There are a number of reamer grinders used by competitive shooters. Pacific Tool & Gauge (AKA "Kiff"), Dave Manson, JGS, and Henriksen come to mind. For some reason, people get downright emotional about who grinds their reamers -- me too. I like Hugh Henriksen, but will allow he can be real slow. As in "Farley time."

As for (1): if you're going to vary from the 105-109 range bullets, which way? towards the 95 or the 115s? I'd suggest toward the 95s, but it's your choice.

Once you decide this one, ASK THE REAMER MAKER. He'll give you the best help; far better than us internet mouse jockies
Click to expand...

Indeed I do agree with you. At 600 yards I see no use of hitting the 115s really. I guess it a mather of taste, as everything else, however if I'd need the extra balistics I guess I could pick another cartridge instead?
__________________________
watch free movies online
 
I've said this soooo many times: There are no prizes in benchrest for highest BC bullet used, highest velocity, etc. etc.

Smallest group, highest score, That is all.

We can all do the math, read the ballistics charts. Most people have found they get better groups (and higher scores) with the 6mms when they don't use the 115s. They work for a few; by all means test them if you want. But if your barrel is like most and prefers the "lighter" 95-108 grain bullets (I forget the jacket length, that is probably more important than weight), your woodpile will grow quicker if you use what it prefers.
 
Bruce
If your dead on at 100 yards you'll need 12 inches of up to be on at 600 yards and the bullet at 600 yards will be going 1998 fps if you were shooting at Sacramento.I don't know the conditions at Ojai but if you have them handy do a Google search for JBM Ballistics Calculator and enter your numbers.I just did that but I used the standard DTAC numbers not the Litz numbers but the website has them all.
I don't use a 6x47 but what you usually notice is a pretty big swing in the velocity numbers between the 105 class bullets and the 115 class of bullets.In something like a 6mm-06 the 105 bullets show best accuracy in my rifles at 3433fps while the 115's show best accuracy closer to 3200fps.If you run the numbers in my example the 105's have a slight edge all things being equal due to the extra 233 fps in velocity.
You will have to chronograph your barrel with all the bullet weights you plan on shooting and see which one wins on the ballistic calculator.
I think what Charles E was getting at is the lighter bullets seem to be winning more fake wood and there is more to it than just the bc number.
If you take two very similar rifle combinations and chamber one in 6Dasher and the other in 300 Ackley you will quickly see why the little 6's are taking home lots of wood.I have 2 of the 75 pound heavyguns in the chamberings listed and everything is equal except for the cartridge.You would think the big 300 Ackley would rule the roost over the dimunitive little 6 Dasher but the targets say otherwise.
The little cartridge burns 335 grains of powder during its 10 round run while the 300 burns over 800 grains.All that extra heat means that around shot number 6-7 the cases will try and stick in the chamber slowing your shot string down.The larger caliber rifle will also recoil farther requiring more time to push it back forward and all of that sawing motion back and farth means the gun will settle more in the bags creating a bigger need for adjusting to prevent vertical stringing.
If you look at the pictures of Joel's gun in the classifieds you will quickly notice how wide the front bag spacing is.When your using tracking rails and the bag settles a small amount you get a certain amount of sideways tilt.If you space the rails farther apart the same amount of settling creates less tilt.
If you come to our next 1000 yard match the first thing you will notice is 3 of my heavyguns now have 18 inch wide forends on them.So far the 300 Ackley is showing the most improvement and I suspect it is from less tilt due to bag settling from the larger calibers.
I would suspect the affects in a 17 pound lightgun to be even more dramatic so I am going to a much shorter barrel with a much wider forend to see if it helps my groups.My thinking is a lighter recoiling rifle with a much wider forend can be shot much faster than the conventional rifles we use now and this will help one make a faster run.
If it works you'll see it at the Nationals in October if not this post is as far as it will go.
Waterboy
 
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I'm not really aiming this post at RBD. When something becomes a religious belief, there is no argument available. Religious truths are *revealed.* As such, they can't be argued. My response is really aimed at others, especially those new to the sport.

RBD said:
Bill Hubina took 7th overall at the NBRSA 600 Yard Nationals, shooting against some pretty tough customers.
Click to expand...

So, if you like something, find someone who won with it, and that is conclusive evidence it is correct? No. In sport, what is correct is what lets you win

RBD said:
But I do, absolutely, believe in physics, ergo, my request for a little quantitative analysis.RBD
Click to expand...
Fine. But go whole hog. You can't take just one small part. Get Bob McCoy's book -- except that is as much engineering as physics. And fairly so. Theory predicts. To the extent that the results don't follow what the theory predicts, you need either (1) find the explanation (refine, add to the theory) or (2) abandon it and get a better predictive model. Factor in center-of-gravity versus center-of-mass offset, and the effect of rate of spin on CG offset. Allow that no bullet or barrel is perfect -- in several dimensions -- and compute the variables that can be introduced by manufacturing both bullet and barrels. Manufacturing may not be a part of physics, but it is a part of shooting.

RBD said:
While your response was, well, a glittering generality.
Click to expand...

Viewed one way. Viewed another way, it is a test procedure to find what works best in your rifle.

For those who don't make a religion of physics, do your testing with an open mind.

[edit]

OK, the above is, I believe, true, but it is also sarcastic. To remove some of that: There is no question that you can build a rifle (eventually) that will perform very well with the 115 grain 6mm bullets. In building anything, you always compromise. Sometimes that compromise is only money, usually it is more. This is engineering, not physics. And the simple, 2010-practical answer is if you want to shoot 115 grain bullets, keep buying barrels until you find one that shoots them well. Do not complain if it won't shoot other bullets well, that wasn't a part of your design objective.

Cheaper is to buy a barrel, and try a few different kinds/brands of bullets. The barrel will show preferences. None of us know why, that is, none of us can measure a barrel and predict "Oh. It will shoot XXX bullets best."

(1) To date, more people are having success with the bullets in the 95-108 grain region. Check the match reports. (2) the optimum rate of twist for 115 grain bullets is greater than needed for bullets on a shorter jackets. They will work, but not (theoretically) as well, due to CG offset and other factors. Practically speaking, there is a range where rate of twist has no adverse consequences, except, perhaps, blowing up bullets due to friction (R.G. Robinett did some work with this with his 121-grain flatbase bullets, not generally available.)

While I haven't set it up in a spread sheet, I do believe that the 95-grainers -- or bullets on that length jacket -- have performed better than the 115s. So, if shooting 115s isn't your prime objective, and you are allowing for compromise in bullet selection (to be determined by testing), that should be a factor in selecting rate of twist.
 
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Lynn said:
Bruce
If your dead on at 100 yards you'll be 12 inches low at 600 yards and the bullet at 600 yards will be going 1998 fps if you were shooting at Sacramento...............
Click to expand...


Bruce,

I don't want to get into any sort of argument with Lynn but this is just flat wrong and will have you bouncing bullets over the berm. If not you it'll be some other poor schmuck reading this for information and headed off to his first match...and since no one else will correct it I guess that leaves me. :(

dead-on at 100 will put you between 65 and 80 inches low at 600 provided your scope offset is 'normal.'

Now, setting your poi 12 inches high at 100 WILL probably get you on paper at 600. This would be 12 inches, or "12moa comeup" in rough terms.

Regarding the rest of the post, I'll just leave it alone. :)

good luck man

al
 
alinwa said:
Bruce,

I don't want to get into any sort of argument with Lynn but this is just flat wrong and will have you bouncing bullets over the berm. If not you it'll be some other poor schmuck reading this for information and headed off to his first match...and since no one else will correct it I guess that leaves me. :(

dead-on at 100 will put you between 65 and 80 inches low at 600 provided your scope offset is 'normal.'

Now, setting your poi 12 inches high at 100 WILL probably get you on paper at 600. This would be 12 inches, or "12moa comeup" in rough terms.

Regarding the rest of the post, I'll just leave it alone. :)

good luck man

al
Click to expand...
Most real 600 yard shooters knew what Lynn meant the way he wrote it :eek::eek::eek:
 
Al is a real shooter, and competes ( and has won some wood) at 600 yards. Even a good guy who knows what he is talking about can ocasionally end up thinking one thing and posting another.
 
The Overall Winner shot 2 different 6.5X47 Lapua's with Berger 130 VLD, Bartlein Barrels, R-15, 205m, March Scopes, and One Panda and One Bat action. Oh and Kelbly 1M stocks. Don

Bruce
I thought this thread was reserved for Lynn and Roberts pissing contest.
 
I thought they were discussing, not pissing. But, I was curious to know why... If someone uses placement in a big match as proof of good performance, they would not choose 1st place as the guideline. Stands to reason doens't it?

I am also intrigued with the fact that the worlds record in 1000 yard benchrest was fired with a B.I.B. Even the name of the bullet is a joke made up by the bullet's maker. And it fits.

Interestingly enough, the second smallest group ever fired in 1000 yard competition was also fired with an "Inferior" bullet. A 200 Grain Brady Knight.

Hmm, I think I"m seeing a pattern here.

Both 30 cals btw.
 
4Mesh said:
I am also intrigued with the fact that the worlds record in 1000 yard benchrest was fired with a B.I.B. Even the name of the bullet is a joke made up by the bullet's maker. And it fits.

Interestingly enough, the second smallest group ever fired in 1000 yard competition was also fired with an "Inferior" bullet. A 200 Grain Brady Knight.

Hmm, I think I"m seeing a pattern here.

Both 30 cals btw.
Click to expand...

It is even worse than you thnk Phil. Brady Knight's die is a clone of R.G. Robinett's -- 10-caliber tangent ogive. I beieve Brady's bullets are on 1.40 jackets instead of the 1.30 of the 187 BIBs. A 10-tangent is a very "unradical" design, but easier to manufacturer. I notice that Berger is trying a mixed tangent-secant point. Brian Litz is a smart fellow. In a much smaller way, I believe using a Whidden point up die on a tangent ogive bullet would be the same. Smaller meplat, though.

* * *

Since Randy's die was for a brief moment half mine, I can say that when it came in, even though it was only guaranteed for 1.30's, Randy felt it was true eough for long enough to use 1.40 jackets, You'd have to twist his arm a lot though . . . Anybody believe in hummer dies?

Even worse, the NBRSA single group 10-shot (HG) record is/was held by Dave Tooley, shooting, you guessed it --the 187 BIBs. It may still stand. And the Australian record is held by Jeff Rogers, shooting, yawn, the 187 BIBs.

BTW, that die is the same one used to make the 118-10 ogive BIB point-blank bullets.
 
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My memory on such things is not so great, but, didn't Sierra, in an effort to make a very high bc 30 call bullet, make some 255gn 30's? Or am I mistaken and it was a 275 or 300gn? I can't remember the weight, but it was a good bit heavier than anything available today. Strikes me Earl Chronister had a bunch of them.

Even withing the same manufacture, it looked to me very early on that bullet weights roughly around the middle of the range within a caliber seemed to work best. Like, the ones that were real heavy, and the ones that were real light, were just not suited to that particular caliber. The ones in the middle were more of a perfect fit. I mean, there's got to be a reason why they stay within those limits. yes?

I had a few thousand of Brady's 200s and thought they were terrific bullets. Great bullet in the wind too. Never shot a bib. Too inferior for me! :D
 
Don
Me in a pissing match you must be kidding.How many reamers did you buy from Robert? They are the standard of the industry and all the big dogs are using his propietary design that is 2 months old now.

Alinwa
Yep he will need to come up 12 inches/moa from his 100 yard zero to be on at 600 yards and his bullet will be going 1998 fps in Sacramento.He mainly shoots in Ojai so his numbers will need some tweaking.

4Mesh
Phil if you notice one thing about all those groups mentioned in this thread shot with the various bullets none of them were shot on the westcoast.If you want to buy some of the Brady Knight 200's let me know.
I did shoot some of the BIB 187's at our last match in my new 300 wsm heavygun in front of 64.4 grains of H4350 and did okay at 600 yards.
Waterboy
 
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