Chambered Round Alignment to Bore; Neck Sized vs Full Length Sized

[Trickymissfit]

I wouldn't buy into Tubbs merchandising hype on a regular basis..
There is nothing special about his dies, especially when they don't match your 6xc chamber(mine didn't -and with a stock Tubb2000!).

Also, I think discussions in reloading about 'what is' and 'what ifs' should steer clear of anecdotal niches.
Competitive Point blank BR shooters have no choice but to FL cases they intend to reload. This, because their winning loads run at extreme pressures way beyond viable for hunting/other cartridges. These high pressure systems represent a major work-around for many reloading flaws. They are more forgiving.
They can get away with it only in tiny cartridges like 6PPCs(223AI capacity) and close to it in 30br(extreme under capacity), and less so still for mid-ranges in 6.5x47(again undercapacity). Beyond these, NONE of it applies.
You could never run a loading scheme like this with something like a 243, 270, 308 or 30-06, no matter the sizing, without a big ol 'bolt hammer' on the bench.
Nor could anyone skip body sizing with a well punished 6PPC, and then be able to machinegun conditions.
So any discussion about it from them could be considered rationalizing of what they must do anyway, and as more niche than basis across the board.

Now someone could decide on a carry varmint gun in 6PPC,, run normal loads with hunting bullets, and probably achieve 3/8moa out to 400-500yds from it(with efforts). In this case there could be little need for FL sizing, if setup for other sizing schemes.
It's a reloading choice. I don't see anything wrong with it, and it's more interesting than turn-key PB BR examples as implied best.

I can understand your thoughts on a die not matching the chamber, and your preaching to the chior. If you ream a chamber with one of the better brand reamers you automaticly double any error ground in the reamer. There is no way out of it. I've never been inside one of the big reamer shops, so I don't know what they are using to grind with, but have a rough idea. I suspect they are are using something like a Starr or a Walther CNC cutter grinder. They will grind a typical reamer to about +/- .000125, or a .00025" window. They will grind closer, but you have to have two grinders that are identical with different wheels plus a lap. The real problem is not grinding the body, but grinding the shoulders and neck concentric with the long taper in the body. But you can get it very close with a lot of crossed fingers and no coffee. So you gt a reamer that has about .00015" error ground in the body and another .0002" in the shoulder concentricity (actually the neck isn't that hard). When you use it those numbers will double even if the barrel is not turning. If you have the barrel rotating at the sametime you automaticly add in the error from the spindle group (bearings, and machine alignments). I had hundreds of reamers ground every year that were very similar to a chamber reamer in steps and sizes, and you soon learn what the nature of the beast is. Plus those two grinders are considered to be the cadillacs of cutter grinders.

Then we get into making dies. Most all are lathe turned, and maybe have a finish reamer run thru them to take the last .005" out of them (or less). I rteally don't know the exact material they are using, but I also know what it's not. I suspect it's 4xxx steel that nitride hardened by the way it cuts. You ream that bore and leave about .0005" in it and have it hardened, and then polish the bore. (I know of at least one die manufacturer that does not polish the bores by the way). That piece of steel will change slightly, and usually less than .001". So you got a really pretty new die set and a finish reamed barrel off somekind of a national match reamer. Guess what? They will not match up exactly. I don't care who made the die or ground the reamer; they never will be near perfect.

As I've said in the past the most accurate reamer on this planet is a Mapol reamer, and they don't come cheap. If a rifle manufacturer decided to use a Maypol reamer to cut his .308 N.M. chambers they would all run with in .0002", but also add about $150 to each rifle. Still every chamber cut would be nearly identical. In theory you could also ream the die with this reamer setup, but who could afford them? I've made forming dies on an Okuma before out of A2. Turned them to size and heat treated them. Still had to polish about .0005" out of them (a real PIA), and I didn't hold the necks all that close (+/-.003", and never could get a really close shoulder concentricity to the body taper (maybe .0015"TIR). And that was by single pointing it with several extremely light passes to take up the tool pressure load. But they were good enough for forming cases, but not good enough for resizing cases in my book.
gary

 

[rscott5028]

I can understand your thoughts on a die not matching the chamber, and your preaching to the chior. If you ream a chamber with one of the better brand reamers you automaticly double any error ground in the reamer. There is no way out of it. I've never been inside one of the big reamer shops, so I don't know what they are using to grind with, but have a rough idea. I suspect they are are using something like a Starr or a Walther CNC cutter grinder. They will grind a typical reamer to about +/- .000125, or a .00025" window. They will grind closer, but you have to have two grinders that are identical with different wheels plus a lap. The real problem is not grinding the body, but grinding the shoulders and neck concentric with the long taper in the body. But you can get it very close with a lot of crossed fingers and no coffee. So you gt a reamer that has about .00015" error ground in the body and another .0002" in the shoulder concentricity (actually the neck isn't that hard). When you use it those numbers will double even if the barrel is not turning. If you have the barrel rotating at the sametime you automaticly add in the error from the spindle group (bearings, and machine alignments). I had hundreds of reamers ground every year that were very similar to a chamber reamer in steps and sizes, and you soon learn what the nature of the beast is. Plus those two grinders are considered to be the cadillacs of cutter grinders.

Then we get into making dies. Most all are lathe turned, and maybe have a finish reamer run thru them to take the last .005" out of them (or less). I rteally don't know the exact material they are using, but I also know what it's not. I suspect it's 4xxx steel that nitride hardened by the way it cuts. You ream that bore and leave about .0005" in it and have it hardened, and then polish the bore. (I know of at least one die manufacturer that does not polish the bores by the way). That piece of steel will change slightly, and usually less than .001". So you got a really pretty new die set and a finish reamed barrel off somekind of a national match reamer. Guess what? They will not match up exactly. I don't care who made the die or ground the reamer; they never will be near perfect.

As I've said in the past the most accurate reamer on this planet is a Mapol reamer, and they don't come cheap. If a rifle manufacturer decided to use a Maypol reamer to cut his .308 N.M. chambers they would all run with in .0002", but also add about $150 to each rifle. Still every chamber cut would be nearly identical. In theory you could also ream the die with this reamer setup, but who could afford them? I've made forming dies on an Okuma before out of A2. Turned them to size and heat treated them. Still had to polish about .0005" out of them (a real PIA), and I didn't hold the necks all that close (+/-.003", and never could get a really close shoulder concentricity to the body taper (maybe .0015"TIR). And that was by single pointing it with several extremely light passes to take up the tool pressure load. But they were good enough for forming cases, but not good enough for resizing cases in my book.
gary

If it's that hard to make perfect chambers and dies and to get cartridges perfectly centered in the chamber after each reload....

How hard is it to make bullet after bullet after bullet, 100's, 1,000's, millions of times.... where each bullet is uniform from one to the next and perfectly concentric, balanced, throughout the full duration of flight, etc... ?

That may be where the most room for improvement is for long range precision. ...notwithstanding practice and reading conditions.

-- richard

 

[Bart B]

If it's that hard to make perfect chambers and dies and to get cartridges perfectly centered in the chamber after each reload.... How hard is it to make bullet after bullet after bullet, 100's, 1,000's, millions of times.... where each bullet is uniform from one to the next and perfectly concentric, balanced, throughout the full duration of flight, etc... ?

Excellent reasoning and question!!!

Bullet balance is probably the hardest to get perfect from bullet to bullet. With all the mechanical parts of a bullet being perfect in dimensions, the microscopic difference in material density makes most of them a tiny bit unbalanced. And that causes different amounts of wobble as they go through the air. Sierra Bullets reported a small spread (1 to 2 percent) in measured BC's based ontime of flight between two points. Even when the velocities were identical going into the first test screen they wouild be different going through the last one; indicating different drag values.

Meplat uniforming of hollow points helps their aerodynamic shape. But I don't think it helps as much as some way to ensure all the bullets one shoots spin perfectly and have consistant BC's from muzzle to target. The only way to check a bullets balance is to spin them at very high speed..

Some tests years ago spinning .3092" 185-gr. Lapua FMJRB match bullets at 30,000 rpm showed about 20% out of a box spun true; the rest were somewhat unbalanced. Some so much so they flew out of the collet chucked up in a Dremel Moto Tool that spun them. The good ones shot several 0.7" to 1.4" 10-shot groups at 600 yards from full length sized .308 Win. cases with neck diameters of about .332" fired in a virtual SAAMI spec chamber with a .344" neck.

 

[Bart B]

Woods states

If you did fire the case with no powder and just a primer then it would have protruded, JUST LIKE THE EXAMPLE YOU GAVE

Varmint Al disagrees.

Mr. Harral says this will happen because the pressure in the case from the primer firing isn't enough to overcome the firing pin force holding the primer well into the case.

He also says some light loads might have enough pressure to lock the brass in the forward position in the chamber but not enough to stretch the web to have the case head to contact the bolt face and push the primer back in.

Woods, I think you might want to do some tests yourself to see what happens when primed cases and rounds without powder are fired. If you post the results, please include all the details including the firing pin's characteristics. Your theories are held by many, but they fly in the face of reality.

 

[Trickymissfit]

If it's that hard to make perfect chambers and dies and to get cartridges perfectly centered in the chamber after each reload....

How hard is it to make bullet after bullet after bullet, 100's, 1,000's, millions of times.... where each bullet is uniform from one to the next and perfectly concentric, balanced, throughout the full duration of flight, etc... ?

That may be where the most room for improvement is for long range precision. ...notwithstanding practice and reading conditions.

-- richard

Bullets vary in diameter and length by the brand and style. But a certain bullet from a certain manufacturer should be virtually the same one right after another, and they all go thru very similar swedging dies. The real differences I've seen are in the ogive and nose tip. Diameters will vary from brand to brand by three to four thousandths of an inch. (.223" to .227"). You can run thousands of bullets thrua good swedging die
gary

 

[Bart B]

Bullets vary in diameter and length by the brand and style. But a certain bullet from a certain manufacturer should be virtually the same one right after another, and they all go thru very similar swedging dies. The real differences I've seen are in the ogive and nose tip. Diameters will vary from brand to brand by three to four thousandths of an inch. (.223" to .227"). You can run thousands of bullets thrua good swedging die
gary

If the jacket material ain't 100% homogenous, all the coin, cup, draw, base shape, lead core insertion and finally pointing the ogive operations performed absolutely perfect will still end up with bullets whose diameters vary and sometimes get egg shaped. Sierra Bullets had problems some years ago with their jacket material they bought from Olin. The stuff they got from Germany was virtually perfect and made some of the most accurate match bullets ever mass produced.

 

[rscott5028]

Bullets vary in diameter and length by the brand and style. But a certain bullet from a certain manufacturer should be virtually the same one right after another, and they all go thru very similar swedging dies. The real differences I've seen are in the ogive and nose tip. Diameters will vary from brand to brand by three to four thousandths of an inch. (.223" to .227"). You can run thousands of bullets thrua good swedging die
gary

We can debate which dimensions/measurements are significant.

But, I can assure you there is meaningful variation between bullets in any box of 500. Bullet sorting by weight, length from base to ogive, etc is well worthwhile for long range precision.

I don't have the equipment to spin the bullets to check for balance as BartB described. But, it makes sense conceptually.

One reason flat base bullets are preferred for short range benchrest is that they are easier to make consistent (hence, more accurate) due to fewer complex angles. As distance increases beyond 200 yds, the better BC becomes more meaningful than any loss of precision manufacturing the bullets.

-- richard

 

[rscott5028]

Woods statesVarmint Al disagrees.

Mr. Harral says this will happen because the pressure in the case from the primer firing isn't enough to overcome the firing pin force holding the primer well into the case.

He also says some light loads might have enough pressure to lock the brass in the forward position in the chamber but not enough to stretch the web to have the case head to contact the bolt face and push the primer back in.

Woods, I think you might want to do some tests yourself to see what happens when primed cases and rounds without powder are fired. If you post the results, please include all the details including the firing pin's characteristics. Your theories are held by many, but they fly in the face of reality.

I suppose these are some of the issues caseless electronic ignition has attempted to overcome.

Yet with all the imperfections of centerfire cartridges dating back over 100 years, it's still not compelling to change.

-- richard

 

[Bart B]

But, I can assure you there is meaningful variation between bullets in any box of 500. Bullet sorting by weight, length from base to ogive, etc is well worthwhile for long range precision.

It may be for some, but I've not seen any difference in accuracy between Sierra's best heavy 30 caliber match bullets so sorted compared to using random selected ones. My 15 to 30 shot test groups at a thousand have produced average 5-shot extreme spreads equal to or better than current benchrest 6-group aggregates.

I think there's other variables, both in the cartridge and between muzzle and target that cause more inaccuracy than a couple tenths grain in weight and a couple thousandths in base to ogive datum. Take a look at a couple dozen pressure curves for rounds with zero spread in component variables to see one of those variables. Too bad exact charge weights, and even weight sorted primers don't produce identical pressure curves.

 

[rscott5028]

It may be for some, but I've not seen any difference in accuracy between Sierra's best heavy 30 caliber match bullets so sorted compared to using random selected ones. My 15 to 30 shot test groups at a thousand have produced average 5-shot extreme spreads equal to or better than current benchrest 6-group aggregates.

I think there's other variables, both in the cartridge and between muzzle and target that cause more inaccuracy than a couple tenths grain in weight and a couple thousandths in base to ogive datum. Take a look at a couple dozen pressure curves for rounds with zero spread in component variables to see one of those variables. Too bad exact charge weights, and even weight sorted primers don't produce identical pressure curves.

I have measured and weighed many bullets (e.g. 107 and 142gr SMKs) and there are measurable differences in base to ogive and weight. Does that cause a meaningful degredation in accuracy? It certainly does in my experience.

But, I will admit that I have not attempted to document the magnitude nor provide statistical evidence. It's just as easy for me to group them in .001" buckets for base to ogive length. And, then follow up by weighing and grouping in .04 grain buckets. Perhaps it's all psychological? But, I sleep well knowing that I did what I could to prevent "unexplained fliers".

-- richard

 

[rscott5028]

It may be for some, but I've not seen any difference in accuracy between Sierra's best heavy 30 caliber match bullets so sorted compared to using random selected ones. My 15 to 30 shot test groups at a thousand have produced average 5-shot extreme spreads equal to or better than current benchrest 6-group aggregates.

I think there's other variables, both in the cartridge and between muzzle and target that cause more inaccuracy than a couple tenths grain in weight and a couple thousandths in base to ogive datum. Take a look at a couple dozen pressure curves for rounds with zero spread in component variables to see one of those variables. Too bad exact charge weights, and even weight sorted primers don't produce identical pressure curves.

Also, you wouldn't mix 155 and 168 gr bullets to shoot those super accurate groups because we know that different shape and sized bullets shoot different.

So, it's simply a matter of how much measurable difference in the bullets themselves it takes to have a negative impact on performance.

It seems that you contend that the amount of uniformity in a box of Sierra match bullets is adequate for serious competition. But, a lot of people either disagree, or won't take that chance.

Either way, the extreme difference in a box of match bullets is likely to be less than a 1 mph wind shift at 600+ yds.

-- richard

 

[woods]

Woods statesVarmint Al disagrees.

Mr. Harral says this will happen because the pressure in the case from the primer firing isn't enough to overcome the firing pin force holding the primer well into the case.

He also says some light loads might have enough pressure to lock the brass in the forward position in the chamber but not enough to stretch the web to have the case head to contact the bolt face and push the primer back in.

Woods, I think you might want to do some tests yourself to see what happens when primed cases and rounds without powder are fired. If you post the results, please include all the details including the firing pin's characteristics. Your theories are held by many, but they fly in the face of reality.

Give a link

You've probably misunderstood something again

 

[Bart B]

Give a link. You've probably misunderstood something again

That was from a private email response from Al Harral. Email him yourself with your issues and questions then you'll get answers straight from Varmint Al's fingertips. That way, you'll bypass any of my BS I you seem to think I've too much of that I asked him about.

 

[TracySes23]

BIG MYTH.


I will say that in the LR game, more than one top shooter has found out that the best concentricity and uniform neck tension is coming from a hybrid technique. They FL size first, use neck expanders (K&M or Sinclair) to expand the complete neck back to nominal caliber and then use a NS only die to neck down to the desired dimension.

For several years it was a very quiet technique but recently has become known more widely.

Please correct me if I'm wrong.

I think I should assume the neck sizing die, should have the ID tailored to work with a specific wall thickness on the neck. This being true, then any neck turning should always give a specific wall thickness to work properly with a custom neck sizing die.

Spencer