Neck "Turning"- the inside, not outside?

[LC Tikka]

Methods of Turning Necks.
On new cases: If the neck inside is concentric with the case body outside, then you could safely outside turn an uneven neck to a uniform neck thickness using current tools and get straight cases. But new cases would most likely not be concentric anywhere so turning new cases is out.
On fired cases: The neck outside would be concentric with the case body, if the chamber is concentric. Then turning the neck inside off the neck outside surface would result in the neck being uniform thickness and now concentric with the case body and also the chamber axis. The bullet would be in the centre of the case and chamber and also aligned with the throat and barrel.

Of course there are some assumptions in the above, but turning the neck inside would seem better than outside IMO.
Are there tools to "turn" inside the neck? (not a reamer)

LC

 

[Preacher]

All you will do is follow the existing hole if you use a reamer to do the inside of a neck.

 

[Sniper338]

Yes there are tools to do it. However most will advise against it. Quick way to mess up brass

 

[pacificman]

There are inside neck reaming tools but Preacher is right as they will just follow the hole.
They won't be able to cut with the accuracy of an outside neck turning tool.

 

[scubohuntr]

I tried inside reaming way back when I was trying to make 7BR brass for an XP100. I never did get a useable piece of brass that way. The few that weren't dangerously off-center had thin spots at the shoulder or cracks. I maybe could have prevented the cracks by thorough annealing of the entire front half of the basic BR case, but by that time I was disgusted with the whole process and never would have trusted the resulting brass. I traded off the XP without ever firing it.

 

[BoydAllen]

There are theoretical problems and then there are real problems. If a neck ID is far enough off center to cause a problem after it is turned and has been fired then the rest of the case has thickness unevenness problems that disqualify it for accuracy work. If you manage to come up with a tool to measure case wall thickness runout down low in case bodies you will learn that runout in unturned necks gets worse as you go down the case. Turning the necks fixes one area, but it does nothing for the rest of the case. Bottom line, there is no substitute for good brass.

 

[Bart B.]

Unless the rimless bottleneck case neck is the same diameter as the chamber neck on a loaded round, its centering in the chamber neck is solely determined by how well centered the case neck is relative to the case shoulder.

Case necks on such cases typically don't touch the chamber neck when fired. The front of the case is centered in the chamber shoulder as the case shoulder's centered there by firing pin impact. Any off-center amount the case neck (and therefore the case mouth/throat holding the bullet) has, it'll be that much off center in the chamber neck.

If the case neck wall thickness varies .001" and the neck outside shape is perfectly centered on the case shoulder, the bullet will be .0005" off center in the chamber freebore and leade. Not a big deal in any discipline as far as I'm concerned.

Note the case neck and bullet will be tilted at a tiny angle relative to chamber and bore axis because the back end of the case body is typically off center in the chamber when round is fired. Not an issue at all. A .001" off center a 308 Win case back end is in the chamber puts its bullet tip about .0005" off center in the opposite direction.

One can usually find good fired brass with uniform wall thickness from head to mouth by checking the pressure ring that's about 2/10ths inch forward of the case head. Here's a Remington BR case in 308 Win once fired:



The pressure ring is higher on one side; that's the thin part of the case wall as shown in the right picture where the case is indexed the other side down It's typically the thinnest part all the way to the case mouth. Use cases with uniform pressure ring heights for best wall uniformity. I don't think a .001" spread is enough to be concerned about; accuracy wise.

Some think the pressure ring high point is where the top of the case was in the chamber when fired. The bottom of the case against the chamber body doesn't expand. Cases don't lay in chamber bottoms when fired. Another popular myth.

 

[Sniper338]

There are theoretical problems and then there are real problems. If a neck ID is far enough off center to cause a problem after it is turned and has been fired then the rest of the case has thickness unevenness problems that disqualify it for accuracy work. If you manage to come up with a tool to measure case wall thickness runout down low in case bodies you will learn that runout in unturned necks gets worse as you go down the case. Turning the necks fixes one area, but it does nothing for the rest of the case. Bottom line, there is no substitute for good brass.

IE: thats why most people use lapua brass

 

[SheepDog]

Since it takes roughly three firings of a case (with only neck sizing) to form the brass uniformly to the chamber (that's why when having a custom die made you need t send in three unsized cases that have been fired three times) and most long range guys are saying they set the shoulder back .002" after the first firing and use that setting from then on, the case is too short to be centered in the chamber. Those who jam the bullet into the rifling are using the bullet and the base of the cartridge to center the loaded round in the chamber. Those who don't jam the bullet into the rifling have the bullet sitting somewhere in the freebore able to move in relation to the bore centerline and able to move back and forth as the extractor will allow.
Now don't take this as criticism because it is hard to criticize what works. What I am pointing out is that with careful workup and tuning of your cases it is still possible to get very good accuracy with good technique and a proper load for the conditions you set. You can ream or turn the necks if you need the clearance but if you don't need the clearance you can leave them alone. There are many ways to get accuracy as long as you have a good gun to start with, but even if you have a 75 year old barrel (like my 3006) that is a bit worn and abused accuracy good enough to keep the groups below 1" is still available if you load for the gun.

 

[LC Tikka]

Yes there are tools to do it. However most will advise against it. Quick way to mess up brass

Have you a link or name for the inside turning tools.
LC

 

[Sniper338]

Have you a link or name for inside the turning tools.
LC

No, Ive seen em before, but had no need to persue it any

 

[jamesdmock]

Methods of Turning Necks.
On new cases: If the neck inside is concentric with the case body outside, then you could safely outside turn an uneven neck to a uniform neck thickness using current tools and get straight cases. But new cases would most likely not be concentric anywhere so turning new cases is out.
On fired cases: The neck outside would be concentric with the case body, if the chamber is concentric. Then turning the neck inside off the neck outside surface would result in the neck being uniform thickness and now concentric with the case body and also the chamber axis. The bullet would be in the centre of the case and chamber and also aligned with the throat and barrel.

Of course there are some assumptions in the above, but turning the neck inside would seem better than outside IMO.
Are there tools to "turn" inside the neck? (not a reamer)

LC

One can turn the INSIDE with an eccentric reamer like the one used in the LEE Target loader kit. It worked well. James

 

[KenOath]

If the inside neck on a new piece of brass is not concentric then how can turning the outside of the neck make it any better?

Cheers Rushty

 

[dannyjbiggs]

K&M makes inside neck reamers. I only use them to take out pesky doughnuts though.

Dan

 

[Shynloco]

IE: thats why most people use lapua brass

About 6=7 months ago, I also started to raise similar questions as the OP. SO I order INSIDE NECK REAMERS from Sinclair who sells them in a variety of calibers. I next took 25 Lapua ONCE FIRED cases in .308 and .260 Rem and turned both the inside and outsides of the necks. I then measured each of the necks in terms of runout and thickness. As an aside, I had to use an oversized mandrel to expand the necks because the reamer would have taken a HUGE amount of brass from the insides of the necks had I not expanded the necks by .001. The runout was performed on a 21st Century Concentricity Gauge and the turning on the inside done on a Wilson Trimmer (which the reamers Sinclair makes are intended to be used upon) and the outsides turned on a 21st Century Lathe. Runout was beautiful and consistent at .0005 - .001, but neck thickness was still reduced from .014 to .007. I then shot each caliber in the same rifle the brass had been fireformed in earlier prior to turning @ 100 yds. Though shot on separate days, I shot both groups (same loads and components) at the same time of the morning with ambient temperatures reasonably (within 5 degrees) using the same rifles and components. The difference in scores was next to zero and IMHO, a complete waste of money (for brass and the reamers) and time to ream which isn't simple to do.

BOTTOM line, IMHO, it is a complete waste of time to ream the insides of the necks of Lapua brass as reducing the thickness of the necks by that much (because the reamer took a large amount of brass out of the neck) thereby shortens the life of Lapua brass and brings on the splitting of necks much sooner than would happen if only the outsides of the necks had been "cleaned up." AND you gain NOTHING in accuracy or your score downrange which are the primary reasons why we try and produce as perfect a cartridge as possible. Just my .02 worth.

Alex

 

[mikecr]

If the inside neck on a new piece of brass is not concentric then how can turning the outside of the neck make it any better?

Neck turning does not make anything 'concentric'. That's not a purpose of neck turning..
You make brass concentric using your best die(your chamber), with fire forming.

 

[BoydAllen]

Some time back (decades), I did an experiment using a tight neck (.244) .222 Remington. Thinking that there might be something to gain, I had RCBS make me a neck reaming die, that would clean up the inside of the neck with a reamer that had a long piot in the die neck, with the neck and body of the case supported by the die. The rest of the neck thickness reduction was done by outside turning. I probably did the whole thing in response to reading The Houston Warehouse once too often. The procedure improved nothing, either as measured by a neck mic, and concentricity gauge (after firing and sizing, or at the target. What it did do was produce a scratchy finish on the inside of the case necks, that seriously increased seating force, until a couple of firings had smoothed things out. Buy the best brass that you can find and if you need to, carefully outside turn it.

 

[KenOath]

Neck turning does not make anything 'concentric'. That's not a purpose of neck turning..
You make brass concentric using your best die(your chamber), with fire forming.

Im a novice at neck turning so trying to understand the basics.
If you turn outside to take out any inconsistencies in brass neck thickness, if the inconsistent neck thickness is on the inside of the neck ie the thicker part of the neck petrudes in not out, would it be of no benefit to turn the outside?
Cheers Rushty

 

[Willie]

New brass typically has tighter necks from the factory, as does new brass FL sized prior to turning. Theoretically, the expander mandrel will force the neck variance to the out side, where it can be removed by outside turning. This is assuming you turn for a tight chamber neck. If doing it to just reduce run-out in your brass, just use a better lot of brass. JMO

Boyd's mention about inside reaming and the change to seating pressure was spot on.

 

[KenOath]

New brass typically has tighter necks from the factory, as does new brass FL sized prior to turning. Theoretically, the expander mandrel will force the neck variance to the out side, where it can be removed by outside turning. This is assuming you turn for a tight chamber neck. If doing it to just reduce run-out in your brass, just use a better lot of brass. JMO

Boyd's mention about inside reaming and the change to seating pressure was spot on.

Ok so you first need to push variances to outside..
I know it's a crude picture but was thinking along these lines.The thicker parts of the neck are supposed to be inconsistencies (exadurated).

Cheers Rushty