Ultimate sizing die ...

[1stmar]

I've been using the lee collet sizing die and I like it very much. However, eventually you need to fl size. I usually get ~3 or so firings before I need to fl size. I push the should back about .002 +\- .001. I like the lee die for a couple of reasons but primarily:
-No lube
-The way it presses against the mandrel as opposed to squeezing then dragging over the expander
-adjustable neck tension based on different mandrels

So why not create a die that works like the lee but also pushes the shoulder back so you don't have to fl size? It doesn't seem like it would be that difficult to manufacture and you could keep the benefits of the lee, include some different size mandrels so you can tune the neck tension to your choice..if you are not sizing the body you shouldn't need lube.

Where am I wrong on this?

[Brian Pfleuger]

I don't see a way of incorporating FL sizing with a collet for the neck like Lee uses.

The next best thing I know of is using the Lee collet dies with Redding Body/Shoulder dies. They do require lube, but you get all the benefit of the Lee collet along with body sizing and shoulder bumping without messing with what the Lee did to the neck.

[rox]

So why not create a die that works like the lee but also pushes the shoulder back so you don't have to fl size?

It's not a collet die, but the Forster Bushing Bump die is one option that's available off the shelf. You can bump the shoulder one or two thousandths, size the neck with a bushing to control neck tension and run it without an expander button. The bushings are cryo treated, so are hard and low friction and I haven't had any problems running the die lubeless (I keep them clean and polished though). It lacks the sliding sleeve of the Redding Competition Bushing die, but I have noticed any worse runout as a result. I don't think it will eliminate the need to FL size occasionally though, since the body size will still increase.

..

[1stmar]

Thx rox, I look into. I like the mandrel as opposed to the bushing because I believe (no evidence to support) that the collet die neck tension will be more consistent. The presumption is, it sizes from the inside where a bushing sizes from the outside and will be much more influential on neck tension due to brass thickness. I have nothing to substantiate this, just theory.

[Brian Pfleuger]

Originally Posted by 1stmar

The presumption is, it sizes from the inside where a bushing sizes from the outside and will be much more influential on neck tension due to brass thickness. I have nothing to substantiate this, just theory.

You and I don't but plenty of people do, and the presumption is correct.

It's not just neck tension either. Expander plugs being pulled out of unsupported necks also tend to pull the neck offline. The collet doesn't pull the neck off-center, which helps make more concentric ammo.

[Bart B.]

Benchresters have known for centuries that best accuracy happens when the case neck's well (perfectly) centered on the case shoulder. As the firing pin drives a rimless bottleneck case shoulder hard into the chamber shoulder, that perfectly centers the case at that point. If the case neck ain't well centered on the case shoulder, it'll be off center in the chamber at that point. Even case necks that have a .001" spread in wall thickness are better centered on shoulders with full length sizing dies. Go measure neck runout on cases relative to the shoulder center (not the body as cases ain't perfectly round) and you'll see the difference.

Any fired case sizing tool and process that doesn't size a case such that its neck isn't centered on the shoulder won't produce best accuracy. Benchresters finally figured this out a decade or two ago and quit using neck only sizing dies of any type including the bump dies that sized necks and also pushed the fired case shoulder back a bit. The only way they could get those perfectly centered case necks on case shoulders was to hold the case body in place while sizing the case neck. Full length sizing dies do this better than neck sizing dies and these are what benchresters use these days to shoot the best groups. Competitors shooting shoulder fired rifles producing the best scores have been using full length sizing dies for over 50 years to do this.

These full length sizing dies have bushings in them a thousandth or so smaller than a loaded round's neck diameter. Their body dimensions are about two thousandths smaller than the fired cases from their rifle's chamber so fired case bodies get sized down about one thousandths. And the fired case shoulder gets set back about a thousandth of an inch, too.

While the benchrester's smallest groups shot still are about the same size, the largest ones that determine aggregate group average are smaller. This is evidence (proof?) that proper full length sizing fired cases produces the most accurate ammo.

One other thing; none of them use a collet die to size necks if they want to be competitive.

The above aside, if one insists on using a collet die to size their fired case necks, go right ahead and do it. Neither the ammo nor rifle knows about it. Otherwise, get a full length sizing die that uses bushings from RCBS or Redding and follow their instructions for picking the right bushing diameter for your cases.

[1stmar]

If the body is round and the neck isn't centered, would that show up as runout measured in the traditional way?

How do you measure runout based on the shoulder center? I use a hornady concentricity gauge, I'm guessing I would need something else.

[Bart B.]

If the case body was perfectly round, you could put it in a V block then measure neck runout or centering with a dial indicator. But neither cases nor chambers nor dies are perfectly round. They're typicaly no worse than 1/1000th inch out of round at best, but some cases are much more so.

As cartridge brass in cases ain't the same thickness all the way around, It won't spring back to perfectly round after sizing or firing. That out of round condition will effect bullet runout numbers when the case body right behind the shoulder is where the front spinner rest is at. Meanwhile, the back of the case rests in another V block or something like that. Cases laying a single V block that contacts the case from its back to the front will have all sorts of variables introduced into the runout numbers. Get a V block and dial indicator set up to measure how round something is, then check your fired and sized cases right behind the shoulder as well as the pressure ring about 1/4 inch ahead of the head.

If you have a cartridge spinner that rests the back end in a V block and its shoulder centered in a round holder (nylon washers work very well), then the case is held the same way as it is in the barrel's chamber. You could use one that has a V block that can let the case shoulder rest on it at mid point on the shoulder. Measure runout at the front of the bullet about 1/10th inch back from its point as well as on the case neck right in front of the shoulder and at its mouth to see how much runout there is all over. I had to make my own 'cause there was none on the market decades ago.

[old roper]

When I started BR we only had the Sako 220 brass. When Laupa made their brass it changed lot of things

Here is real reason BR FL size

Custom Dies Work Best
Most top 6PPC competitors run their ammo at pretty high pressures. Such pressures demand that cases be full-length sized each time they are loaded. But the trick is sizing the case just enough to allow proper feeding/extraction and no more. To achieve this perfect fit, nearly all the "top guns" use custom dies, precisely fitted to the dimensions of fired brass. Typically, a custom sizing die will reduce the case diameter at the shoulder .00075" to .001". The die will also allow for a little bit of shoulder bump. Nearly all the top shooters use bushings for neck-sizing. Having a variety of bushing allows you to compensate for brass that becomes work-hardened. You can also use bushings to tune loads for different bullets or conditions (tighter "grip" tends to increase pressure). For his .263"-necked brass, Speedy Gonzalez has a full set of carbide neck bushings, in .0005" increments from .256" to .261". He also has four different body-sizing dies, which allow him to choose the exact amount of sizing he wants, both at the shoulder and at the web.

I should add other improvement was Redding Small Base type S sizer for the 6ppc as some made reamer for that die.

http://benchrest.com/showthread.php?...e-die-question

[Bart B.]

I like this about full length sizing:

But the trick is sizing the case just enough to allow proper feeding/extraction and no more.

From what I've seen and learned over the years, how much is "just enough" varies between those shooting bullets the most accurate. Some folks so a lot, others very little, in how much fired case diameters and shoulder setback is used. The most consistant between them is the case shoulder. The limit seems to be 2 thousandths for 30 caliber and smaller. Some folks reloading for 33 caliber super magnums go 3 to 4 thousandths and the 50 caliber BMG crowd as much as 6 to 8 thousandths.

[old roper]

Bart B, the guy who wrote that article is Speedy and he is now teaching down in Trinidad.

http://staging.outdoorhub.com/news/n...nmakers-guild/

As to the article is was about the 6ppc and nothing else.

[1stmar]

I see potentially conflicting data as it relates to production rifles and dies. I have no doubt you guys are correct wrt bench rest shooters with custom rifles and dies. However in factory rifles and factory dies, the case will expand to roughly the size of he chamber. By resizing the case it will be below the recommendations old roper mentions where case tolerances are minimized and only sized enough to extract. This makes sense and likely helps keep consistent pressure. So given that factory chambers are likely on the sloppy side, perhaps not resizing the case body achieves or approximates this goal? Since there is really no way to know for wether case to chamber fit or neck/shoulder centering is more advantageous, given factory rifles it seem plausible that not resizing the case body may be better and doing the best you can to ensure concentricity will help minimize the effects of off center necks.

[old roper]

1stmar, You are so very right as to factory chamber vs customs chambers.

Myself I neck size if I was matching shooting with the 6ppc I'd may do thing different and for my 6ppc I use for varmints I see no point in running them that hot.

[Bart B.]

1stmar, every case expands to the chamber dimensions behind the neck when they're fired.

Now, about how a case fits the chamber. Especially this case to chamber fit or neck/shoulder centering and which is more advantageous. Think a bit about what I'll explain.

Take a .338 Win. Mag. chamber. It's got a diameter at its shoulder at the body part that's .491". The shoulder angle's 25 degrees. So there's part of a 50 degree V at the front of the chamber. And the chamber neck diameter's .370".

Now drop a .308 Win. case in the chamber with the muzzle pointing straight down. That case has a .454" shoulder diameter at the body. Its shoulder angle's 25 degrees; part of a 50 degree V at the front of the case. Its neck diameter's .338"

Where' the .308 case shoulder going to center from gravity pulling it down in the .338 chamber?

A .243 Win. case has the same case dimensions as the .308 case except its neck is .276" in diameter. It's also got a 50 degree V section at its front at its .454" diameter shoulder. If this case is dropped into the .338 chamber, how will it center in the chamber shoulder?

Which case will center more perfectly in the .338 chamber's shoulder?

If all cases' necks are perfectly centered on their shoulder, which one will be more perfectly centered in the .338 chamber's neck?

This is exactly the same as dropping, one at a time by itself, a marble, a ping pong ball and finally a cue ball into a funnel with its nozzle pointing straight down. Which one will more perfectly center in the funnel at its bottom?

[1stmar]

The case that is the largest and fills the chamber the best would minimize tilt in the chamber and settle the closest to center. But wouldn't this make the case to not fl size and keep the body as large as possible, there by minimizing tilt and keeping pressure consistent? With loosely cut shoulders on factory barrels you'd likely never match the should cut in the chamber to the shoulder on the case, fl sized or not. So minimizing neck sizing, maximizing oval so that the bullet touches the rifling would help center the cartridge. This might explain why some rifles work best that way (sloppier cut chambers) and some don't (more concentric chambers)

[Bart B.]

1stmar, rethink this again. Compare this to stacking paper cups, one inside another. Do they tilt relative to each other?

[1stmar]

I get what your driving at just not sure I agree. The rifle is not vertical it's horizontal with the rim supported by the bolt. The weight of the rim is significant, as are the dimensions of the rim, bolt face, the length of the chamber relative to the length of the cartridge, the length and dimension of the neck... When the firing pin strikes the primer, ignition starts, there is slop, so the case doesn't fill the chamber and press against the shoulder until some point of pressure build. This is when the case centers or tries to center itself in the chamber. If the bullet releases before the case is fully expanded it will not be as centered as it could be. If the case started against the shoulder and was pressed into the chamber I would agree with the analogy.

[Bart B.]

1stmar, a chambered round's back end is pressed against the chamber wall by the extractor. If the back end of the case is .002" smaller than the chamber diameter at that point, the back end will be .001" off center. External claw extractors push the case head to one side, sliding extractors in the bolt face (push feed Win. 70's] push the case head up.

If the bolt has an in-line spring-loaded ejector in the bolt face, that pushes bottleneck cases headspacing on their shoulder full forward until its shoulder stops against the chamber shoulder. And that very well centers the case shoulder in the chamber shoulder.

When the firing pin falls, that further drives the case shoulder hard into the chamber shoulder. The shoulder's typically set back a thousandth or more from the force of the firing pin's impact. The case is perfectly centered at its shoulder when the round fires. Doesn't matter how much clearance there is around the case body behind the shoulder; it's perfectly centered.

If a case is .001", or even .002" inch off center at its back end, that'll put the bullet's tip in a round with zero bullet runout about half to three-fourths that much off center in the bore. But every round chambered will have the same error; every round's repeatable in how it's chambered. Every rifle made does this; benchrest, match rifle, or sporting rifle with a standard SAAMI spec chamber. There's no such thing as a perfectly centered back end of a bottleneck case in its chamber; external force from the extractor pushes it off center. Doesn't your bolt's extractor hold a case in place on the bolt face if it's out of the receiver?

The .308 Win. and .243 Win. case necks in that .338 Win. Mag. chamber will center perfectly in it as the shoulder angles are equal. There'll be full contact around the case shoulder to the chamber shoulder. The back end of the cases will center in the chamber. Although both cases will have a lot of clearance around them, they are perfectly centered, just like the paper cups are relative to each other.

[1stmar]

My bolts are all claw extractors (rugers). Not trying to be argumentative. The theory sounds logical and as previously said, I'm confident br rifles perform as you have indicated. My personal experience so far does not bear this out (fl sizing demonstrating better performance). I'm fairly anal about my approach or at least I try to be. I do not go to what I will call extremes (neck turning for example) But I do weigh each case, charge, bullet etc, prepare cases the same way and in fact use the same cases. On every 4 or so reloading when I need to fl size it appears my group sizes are larger on average. I'll do some more conclusive testing. I use quality components (redding dies fl sizing dies) and I compare shoulder pre and post sizing. I am rarely pushing the shoulder back more then .002. There is an occasion where too much lube cause the shoulder to go back .004 but that is the exception. So the only conclusion I can draw if reality proves me right, is that the tolerances play more into this.

[Brian Pfleuger]

Though I can not give specific examples in terms of numbers, I have seen indications by folks who know that some things that work in ultra-high precision, BR type rifles can have no discernible effect in "normal" guns.

UncleNick has discussed runout as one such example, IIRC. Small runout makes "big" (percentage big) changes in group size in a rifle that shoots tiny groups but much more severe runout makes no detectable difference in "normal" guns.

In other words, a normal gun might be capable of 2/3s MOA, for example. A BR gun might shoot 1/8 MOA at 100 yards. Getting that 1/8th requires considerable prep, extreme care and expensive dies/equipment. Shooting that same ammo in the "normal" gun gets you... 2/3 MOA. Using collet dies gets you.... 2/3 MOA.

In theory, better. In practice, irrelevant. Not if you're using that BR gun, but a normal gun.

Also, there's the idea of "OK, I cooouuuullllddd get better groups, like 2/5th MOA if I did A, B, C, D, E, F, G.... but I'm only shooting at deer (or even woodchucks) so I can get 2/3 MOA by doing A, B, and C and skipping all the rest. So, why bother, all my targets are MUCH bigger than 2/3 MOA.

[Bart B.]

1stmar, try full length sizing with a bushing die (no expander ball) and set the fired case shoulder back no more than 2 thousandths. Decap, clean then lube the cases before sizing. And the bushing diameter needs to be about 2 thousandths smaller than a loaded round's neck diameter.

It's not uncommon for some folks to get better accuracy with neck only sizing tools and techniques 'cause of the way the set up and use their full length dies.

[old roper]

I got to say this. BR shooters are different in that some shoot short yardage game 100/200 and 300yd and they load at the range. Accuracy is conditions that may require changing loads and it can be from seating depth to neck tension etc.

If you look at those that shoot 600yd and 1000yd BR match that's different loading.

It's not a one size fit's all. If you look at the post I posted from 6br on F-Class open rifles and how they load that might differ from other type F-Class rifles so what Bart B maybe talking about without understand what type match rifles he's talking about is useless unless you can link it what match rifles he's talking about.

[Bart B.]

I'm referring to short, medium and long range competition. Benchrest, F-Class or High Power rifle. High Power folks' been full length sizing (without expander balls) since the late 1950'a. F-Class started out by High Power shooters using a rest under their rifle's fore end slung up in prone; they, too use full length bushing dies. Benchresters started using full length bushing dies a decade or more ago. And Sierra's been testing their bullets with full lenght sized cases since the early 1950's.

[1stmar]

What's a 4th set of sizing dies :-)) I already have 2 fl and and the lee. Maybe 1 more is the charm. I really hate lubing, I have to admit its one of the reasons I really like the lee.