Why Turn Neck Exterior?

[DngBat7]

So, here is my question for the Benchrest guys or “pro” neck turner. Why turn the outside of a neck? I can imagine that turning the “inside” of a neck would make a difference. Centering the bullet. But why the outside? When the brass is sized, the neck is not touching the inside of the chamber of the rifle. When the bullet is fired, the bullet is long gone before the expanded neck diameter makes a difference in the trajectory. So, where does exterior neck turning come into play? The only place I can rationalize is if you have a tight custom chamber????

Thanks.

 

[fingers]

When you use an expander mandrel in the neck you push all the irregularities to the outside of the brass. After this is done turning the outside of the neck takes out these irregularities and uniforms the neck thickness, giving a more centered bullet alignment & uniform neck tension & more uniform bullet release. It is not just the bullet release of the single round but to make all the necks as close to the same as you can manage. Round to round uniformity is the focal point of accuracy. Hope this helps.

 

[BoydAllen]

In many cases, turning necks may not improve accuracy. If there is some other more important factor that is limiting accuracy, any potential benefit of turning may be lost in the noise. One of those possible factors is the shooter and the decision that he makes about how to attain the best accuracy that a rifle has to offer. Many times I have seen shooters choose to ignore important details because they did not want to be bothered with them only to obsess over things that were relatively unimportant. Accuracy is a weakest link thing. Getting back to the question, what is your most accurate rifle, and how do you go about tuning and shooting it? What is the trigger's pull weight, and what sort of scope, rest, and bench are you using? Are you using any sort of wind flags?

 

[T-shooter]

Turning the outside should make the inside and outside concentric. Most dies center the case and outside of the neck together. If the neck had thicker and thinner sides, then the bullet won't be in the centerline of the case.

 

[BoydAllen]

Being more specific. My fired cases' runout is generally around .0003 or better. The necks had more thickness runout than that before they were turned, so even though the necks were turned off center to the body (assuming that the shape of the case if formed with reference to its exterior only) The pressure of firing centered the neck on the body.

New .220 Russian cases have about .002 runout at the ends of their case necks. I would guess that the process of expanding them up to 6mm with a mandrel may in many cases double that. It would not be practical to straighten an unfired case so that its exterior was perfectly straight, so that you could then bore the neck's ID so that it would be both concentric with the OD and coaxial with the CL of the body of the case. My advice is to copy what the better shooters do until you can shoot better than they do, and when that happens go looking for better methods.

 

[LC Tikka]

So, here is my question for the Benchrest guys or “pro” neck turner. Why turn the outside of a neck? I can imagine that turning the “inside” of a neck would make a difference. Centering the bullet. But why the outside? When the brass is sized, the neck is not touching the inside of the chamber of the rifle. When the bullet is fired, the bullet is long gone before the expanded neck diameter makes a difference in the trajectory. So, where does exterior neck turning come into play? The only place I can rationalize is if you have a tight custom chamber????

Thanks.

Technically turning the case neck inside is better all round. As no one including the better shooters has come up with a method to turn (not ream) inside "we" will just have to do what everyone else does. If we all turn outside it must be right!!
LC

 

[spclark]

As no one including the better shooters has come up with a method to turn inside....

????

What do you think neck reamers are for if not uniforming or ‘turning’ case neck ID’s?

Admitting that they’re likely less commonly used by reloaders than neck turning apparatus, neck reamers have a place in some case prep disciplines.

When I first ventured to produce 6XC cases from Lapua’s Palma 308 brass I felt it necessary and appropriate to use both case neck reamer and neck turning to reduce neck thickness.

Forming 0.015+” 308 necks down to 6mm ID dimension then turning off the excess produced more run-out than when I went beyond moving brass down to 6mm ID so I could then remove some of the extra metal by reaming, the rest by turning (a little here, a little more there).

More recently, with the introduction of 6.5 Creedmoor factory cases used as parent brass, such radical operations aren’t required. 6.5 necks didn’t need reaming once sized to 6mm; there’s less material being forced into a smaller neck ID with fewer irregularities to have to uniform.

 

[DngBat7]

????

What do you think neck reamers are for if not uniforming or ‘turning’ case neck ID’s?

Admitting that they’re likely less commonly used by reloaders than neck turning apparatus, neck reamers have a place in some case prep disciplines.

When I first ventured to produce 6XC cases from Lapua’s Palma 308 brass I felt it necessary and appropriate to use both case neck reamer and neck turning to reduce neck thickness.

Forming 0.015+” 308 necks down to 6mm ID dimension then turning off the excess produced more run-out than when I went beyond moving brass down to 6mm ID so I could then remove some of the extra metal by reaming, the rest by turning (a little here, a little more there).

More recently, with the introduction of 6.5 Creedmoor factory cases used as parent brass, such radical operations aren’t required. 6.5 necks didn’t need reaming once sized to 6mm; there’s less material being forced into a smaller neck ID with fewer irregularities to have to uniform.

So with the exception of a wildcat cartridge to create the desired neck thickness, which is more important. I’d neck reaming vs od neck turning?

 

[mikecr]

Even a caveman can turn necks to beautiful results.
Reaming on the other hand, could be difficult to impractical for the same results.

Think about it; to ream necks to a goal thickness means first getting necks to what diameter to cause that? You would push a reamer into springy necks, that spring back causing ever changing forces against the flutes, and as it hogs away on the ID, what do necks spring back to that would leave you with the right thickness?
Could you predict it? I don't think so, not even close.
Do people actually do it? Well, some fool could put so much effort into what everyone else does with ease.
Some fool..

Your cases are made straight with fire forming, using your best custom die (your chamber).
Get your desired thickness for clearance, tension, low runout, and fire form to make your brass what it will become. Here, existing thickness variance is slammed inward. You follow sizing with expansion to push thickness variance back outward -away from seating bullets.

You can mitigate donut formation with neck turning. And you can later ream out ONLY the donut area forming since. But even this small amount of reaming can be a nightmare for your necks (because of spring back). So it's best to plan for donuts where they can be as they are down the road, and not affect you anyway. Things like never FL sizing necks, and never seating bullet bearing into donut areas.
TAH-DAH,, donuts no longer matter.

 

[carlsbad]

As mikecr says, reaming (properly) would not be easy.

If I needed to design a reaming process for necks (and this may have already been done) I would consider devising a method to secure the case inside a resizing die and mount the die in a collet. Still not sure this would work because of springback.

Turning the outside is the way to go.

 

[tmwinds]

If the neck of your loaded round is at least .002 less than your chamber neck you are good to go. Otherwise you need to turn to get the proper clearance for safety reasons. I will leave it to others to discuss any accuracy improvement. I've never seen it.

 

[Catfur]

????

What do you think neck reamers are for if not uniforming or ‘turning’ case neck ID’s?

Reaming follows the existing hole, enlarging it by a set amount, so if the neck is uneven, the new, larger hole will be uneven as well. Turning the outside makes the neck even all around.

 

[DanS]

Inside neck reamers are good for removing donuts inside the case.

Dan S I like outside turning to achieve even neck wall thickness.
DanS

 

[Bart B.]

If the case neck is perfectly centered on the case shoulder and the neck wall has a .0010" spread in thickness, the bullet will be .0005" off center in the chamber neck, freebore and throat when it fires.

Even if it's a 243 Win cartridge in a 308 Win chamber.

 

[Richard Coody]

So, here is my question for the Benchrest guys or “pro” neck turner. Why turn the outside of a neck? I can imagine that turning the “inside” of a neck would make a difference. Centering the bullet. But why the outside? When the brass is sized, the neck is not touching the inside of the chamber of the rifle. When the bullet is fired, the bullet is long gone before the expanded neck diameter makes a difference in the trajectory. So, where does exterior neck turning come into play? The only place I can rationalize is if you have a tight custom chamber????

Thanks.

depends on what you are trying to do. for the average shooter there is no reason. if you are looking for another tenth of reduction in group size then there is all the reason in the world.

you want uniform brass thickness in the neck for your entire batch of brass. helps with concentricity and neck tension. i see no benefit from reaming over neck turning for what you are trying to accomplish. Even removing donuts is much easier accomplished by using a mandrel to move it to the outside and turn it off.

for you i doubt there would be any benefit to either.

 

[retired]

actually we turn the outside,
because we as shooters have
NO PRACTICAL WAY TO LINE BORE THE INSIDE.
so we settle for od turning

 

[butchlambert]

I have reamers to ream the ID and after fireforming with out a bullet the first time I turn the outside. Does it help? Not that I can ascertain.
I might need to clarify this. I used to inside ream and then fireform without bullets in a fireforming bullets. I only needed to expand only slightly and then turned the outside. They shot just as well without inside reaming first. This is PPC only.

 

[Webster]

Reaming follows the existing hole, enlarging it by a set amount, so if the neck is uneven, the new, larger hole will be uneven as well. Turning the outside makes the neck even all around.

If you ream wouldn't you need a set of reamers in 0.0001" increments to control how much material you remove. The reamer follows the contour of the neck. It isn't a center line boring operation. The worlds best SR bench rest shooters don't inside ream to the best of my knowledge. Correct me if Tony Boyer does it different. In order to O.D. turn you have to run an expander mandrel (one std diameter) inside the necks to get a tight fit on the neck turner mandrel. Then neck turn. This seems to be good enough for the worlds best SR competitors. An inside expander mandel pushes the high spot and a large area around it outward. Impossible to push just the high spot outward. The springback is probably greater than the high spot that got pushed outward. Bottom line I will only O.D. turn.

 

[danny]

As mikecr says, reaming (properly) would not be easy.

If I needed to design a reaming process for necks (and this may have already been done) I would consider devising a method to secure the case inside a resizing die and mount the die in a collet. Still not sure this would work because of springback.

Turning the outside is the way to go.

The Wilson Trimmer does this, essentially. The case holders are more or less open-ended dies, and they sell reamers.

Danny

 

[KMart]

[QUOTE="carlsbad, post: 37246641, member: 1287427"
If I needed to design a reaming process for necks (and this may have already been done) I would consider devising a method to secure the case inside a resizing die and mount the die in a collet. Still not sure this would work because of springback.
[/QUOTE]

The Guffster made a reference to that die or dies in one of his posts.

my reamers do not work unless I have outside neck diameter support. I have one reamer die and one reamer for that die, it is a 243. The die is a full length sizing die with a opening in the top of the die that is a guide for the reamer, there is no way to ream a neck more accurately than with a reamer die and reamer. And then there are those that talk about it, before that R. Lee made a set of dies he called Target Models, the sizing die was not a full length sizing die but the die was designed like the RCBS reamer die, the lee dies came with a reamer that fit the top of the die and guided the reamer through a guide hole.