Acceptable neck thickness variation?

[johara1]

what if you run a mandrel to push out those tiny variations? I mean after turning the next to the desired thickness... different size mandrels could be ordered for different neck tensions...
Anyway, just curious to hear the comments?

The expander mandrel needs to fit the mandrel on the neck turner with the proper clearance.... jim

 

[rardoin]

what if you run a mandrel to push out those tiny variations? I mean after turning the next to the desired thickness... different size mandrels could be ordered for different neck tensions...
Anyway, just curious to hear the comments?

Yes, that can be done, and is done. You need to have an assortment of mandrels control the neck expansion (with spring back considered) to match the desired difference between the neck ID and the bullet OD. Posts on this site concerning this topic may pop up in a search.

 

[johara1]

Yes, that can be done, and is done. You need to have an assortment of mandrels control the neck expansion (with spring back considered) to match the desired difference between the neck ID and the bullet OD. Posts on this site concerning this topic may pop up in a search.

NO, you are missing the point. The expander mandrel is used to make a good fit for the neck turner only, one maker expander mandrel sure doesn't work for an others neck turner. i do not ever expand the neck to get the proper neck tension, that is done with a neck bushing from the outside... it is just an other chance for miss alignment ..... jim

 

[Shynloco]

Alright guys, not trying to start a deeper discussion or disagree with anyone's methods of precision case preparation. But I'm suddenly learning my Starrett and Mituyoto mics and calipers must be junk at least cheap as I see the Starrett tube mic sells for $600. Now with that comparison in mind, does that mean my Sinclair and 21st Century Turning tools are inferior to a Forster or other similar models of turning tools or do they cut also to such a tight variance as .0001? Personally, I've been turning casings to within .001 variance and have been getting very good results over the years down range on my targets. So am I settling for a lesser precise finished casing? Thx.

Alex

 

[johara1]

Alright guys, not trying to start a deeper discussion or disagree with anyone's methods of precision case preparation. But I'm suddenly learning my Starrett and Mituyoto mics and calipers must be junk at least cheap as I see the Starrett tube mic sells for $600. Now with that comparison in mind, does that mean my Sinclair and 21st Century Turning tools are inferior to a Forster or other similar models of turning tools or do they cut also to such a tight variance as .0001? Personally, I've been turning casings to within .001 variance and have been getting very good results over the years down range on my targets. So am I settling for a lesser precise finished casing? Thx.

Alex

Alex, I have a 21st century neck turner and it does the same and i have an old Sinclair but it isn't in the ball park. and the K&M, 21st century and the Pumpkin will hold a .0001 and i use both the makes of Mics. as you but my Mituyoto calipers are not used in neck turning measurements..... jim

 

[Shynloco]

Thx Jim,
I glad to read my 21st Turning Tool isn't junk. I bought it several months ago as an improvement over my older Sinclair NT1000 that I'd been using previously. So apparently my measuring tools simply may not be capable of getting that fine a variance as you and other are able to.

Alex

 

[Tim Singleton]

Alright guys, not trying to start a deeper discussion or disagree with anyone's methods of precision case preparation. But I'm suddenly learning my Starrett and Mituyoto mics and calipers must be junk at least cheap as I see the Starrett tube mic sells for $600. Now with that comparison in mind, does that mean my Sinclair and 21st Century Turning tools are inferior to a Forster or other similar models of turning tools or do they cut also to such a tight variance as .0001? Personally, I've been turning casings to within .001 variance and have been getting very good results over the years down range on my targets. So am I settling for a lesser precise finished casing? Thx.

Alex

I'm not meaning this in a bad way at all. But if the results you are getting are good then I wouldn't worry about fixing what ain't broke. I don't know what range you shoot or what is acceptable.

Tim

 

[johara1]

Thx Jim,
I glad to read my 21st Turning Tool isn't junk. I bought it several months ago as an improvement over my older Sinclair NT1000 that I'd been using previously. So apparently my measuring tools simply may not be capable of getting that fine a variance as you and other are able to.

Alex

i'm sure your tube mic. and i" mic. are capable of measuring a .0001 If it is marked on them......... jim

 

[mikecr]

My Sinclair mic measures to 0.00005"
As for turning adjustment, this is ALWAYS trial & error until it's right, and then requiring the skill to keep it right.
If my necks aren't within .0001, they're damn close to it(with Sinclair).
And if I could do no better than 1thou, I'd give up the turning endeavor(and probably reloading by that point). I don't even keep, much less bother to prep brass, unless well below 1thou in thickness variance to begin.

 

[Shynloco]

Jim and Mike,
None of my mics are like Mike's pictured Sinclair mic or the Starrett Brownell's sells. And you are right about learning to turn brass and then maintaining that repeatability. Talent and practice sometimes makes the difference as well. Personally, I only clean up brass anymore and do not compete where that tight a tolerance could make or break winning a competition. But I must say this whole topic is very enlightening and has taught me more about how much more detail a reloader can do to either "get an edge" or to pursue "perfection", all of which may well show upon a target downrange. So though I was pessimistic about achieving such measurements at the beginning of this topic, I now better understand how one can approach and achieve that stated tolerance and be able to measure it. Thx guys!

Alex

 

[Shynloco]

I'm not meaning this in a bad way at all. But if the results you are getting are good then I wouldn't worry about fixing what ain't broke. I don't know what range you shoot or what is acceptable.

Tim

Thx for the thought Tim. But at the same time, the question now remains, can I do this even better and if so, I may have just learned how I can get there. Personally, I love a challenge in reloading, especially when someone has enlightened me about something I didn't know about. And I guess I can be my own worst enemy, when I hear about a new and better way of doing something. Kinda gives me an itch and desire to find out. Guess that's another bye product of this site, in helping me achieve a goal and get closer to poverty. (lol)

Alex

 

[Tim Singleton]

I'll add this. If the rifle, scope and the rest are not up to the task of achievIng the kind of accuracy that turning necks to the tolerances we are speaking of is required.
You may very well never decern it on the target
It takes a rifle and shooting system at the extreme edge of accuracy to see this. My opinion and $2.50 will get a cup of cheap coffee

 

[LHSmith]

The trick to maintaining 0.0001" is using a well designed cutting tool and precisely matched expander to the turning mandrel AND knowing how to keep everything iso-thermal when turning and measuring. Tricks learned long ago by the legendary custom bullet makers on how to maintain the same temp's during critical bullet making operations. Again, the #1 tenet in BR " do everything exactly the same every time - eliminate as many variables as possible" applies here.

 

[LHSmith]

My Sinclair mic measures to 0.00005"

A mic that reads to 50 millionths is well beyond it's limits to read that small accurately.
Fowler, the OEM, lists the accuracy as +/- 0.00016.

 

[johara1]

I thought i would never say this but the Pumpkin is the easiest and most repeatable neck turner i have. The others are very accurate and it is a PITA. to get them set....... With the mic. you need to develop a feel and don't look at the numbers doing it. Brass is soft and it is very easy to get different readings....... jim

 

[TrapperT]

I'm going to echo Tim's statement.

If the rifle, scope and the rest are not up to the task of achievIng the kind of accuracy that turning necks to the tolerances we are speaking of is required.
You may very well never decern it on the target

I have a very good mid range F-Class gun chambered in 6mm Dasher. My neck diameter is such that I am able to shoot turned and unturned necks. I have shot both types of brass in competition and what I have found is that the turned necks yield a few more X's over the unturned. IMHO, you gain more accuracy from the bullets than turned necks. Granted, turned necks don't hurt, but turning them so they are all identical still won't make up for other issues (if there are any).

Tony

 

[nmkid]

It takes a light touch and time with someone who knows to learn how to properly use a micrometer

I agree. Honestly, I couldn't get the "feel" with a micrometer and finally gave up. Darn 10 thumbs!!

 

[johara1]

I'm going to echo Tim's statement.


I have a very good mid range F-Class gun chambered in 6mm Dasher. My neck diameter is such that I am able to shoot turned and unturned necks. I have shot both types of brass in competition and what I have found is that the turned necks yield a few more X's over the unturned. IMHO, you gain more accuracy from the bullets than turned necks. Granted, turned necks don't hurt, but turning them so they are all identical still won't make up for other issues (if there are any).

Tony

Tony, Ay mid range the record in bench rest is under .4 yes it matters. All things matter, a dasher at 1000 yds can shoot 30 shots in a little over 3" it did leave much on the table. It is a sum of a lot of little things, the big thing is the wind. That is your department....... jim

 

[ireload2]

There was a federal government standard for micrometers that are used for work on government contracts.
It was GGG-C-105C. This standard was canceled in 1996 but you can still find a copy of it at the US govt assist quick search site
http://quicksearch.dla.mil/Transient/AFADCE74D6814624A29B204EC355B2F4.pdf

This is a Mitutoyo web page that compares Mitutoyo's internal standards with the federal standard GGG-C-105C
http://www.auto-met.com/mitutoyo/micrometer/mitutoyo_micrometer_l-02.pdf
There might be several ways for the curious to build a case neck measuring system that would be better than an off the shelf tube/ball micrometer.
1. Use a 3" diameter micrometer head that direct reads .0001 on the thimble.
2. Put together a tool using a .000020 resolution indicator.

Bear in mind that temperature stability is required to get proper meaningful results.
Also bear in mind that you cannot inspect in the quality. You get quality by controlling the process.
Culling parts produces a lot of scrap. Control the process well and all of your necks will be good.

One way to control the process better would be to press the case necks onto a pilot mandrel in a lathe collet.
The mandrel is machined in the lathe prior to machining case necks so you know it has no run out other than what is in the lathe spindle bearings.
However this lathe has to be a good one. You will not get better accuracy using a sloppy cheap lathe.
Turn the case neck and verify the diameter before removing the case from the mandrel using something like an Etalon or Mahr indicating micrometer with .000020 resolution. Wrapping the frame with some sort of insulating material would also help.
This process has an advantage in there being no movement between the mandrel an the case neck when it is turned.

This indicator is shown attached to a Federal Mahr bench mike on Ebay.

 

[Alex Wheeler]

To understand what kind or tolerances or variations you should except, I find it easier to convert thing into a %. If your necks are .012" thick, .001" is a 8.3% variation, .0001" thickness runout is a .83% variation. And yes, set up right you can hold +/- .00005". Keep everything temp stable including the mic.