Which is best?

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Ross Smith posted this 11 December 2022

I just finished forming, sizing ,trimming ,and neck reaming some 308x1.625 cases from 308 cases. For me I then inside neck ream with a .311 reamer after neck sizing in a 308x1.5 die. 

Is outside neck reaming better? Seems like all the jb guys outside neck ream.

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RicinYakima posted this 11 December 2022

The theory is that outside neck turning against a mandrel makes for a more even wall thickness. They say a reamer will follow the thin side of the original neck. I have no opinion one way or the other. I outside neck turn but only because that is the tooling that I own. 

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Wm Cook posted this 12 December 2022

Ross have you always inside reamed?  Since I've only outside neck turned these past 30 years its all I know. 

I think that turning the outside necks down to and including the shoulder would maybe improve fire forming to prevent inside bulging where the neck meets the cast body.  2.015 down to 1.625 seems to moving a lot of brass around.  Is it possible you need both? 

I didn't help did I.  More questions than answers.  I'm looking forward to what others think.  Take care, Bill.

 

Patience isn’t a virtue, it’s a delay tactic.

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Pentz posted this 12 December 2022

Read the last issue of TFS.

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Wm Cook posted this 12 December 2022

Are you referring to "More Variation in Neck Tension" in 279?  Bill C.

Patience isn’t a virtue, it’s a delay tactic.

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Ross Smith posted this 12 December 2022

Ya'll: I inside neck turn because when forming my cases for 308 cases, the new OAL is down into thicker brass from the 308 cases. I get a dougnut right of the bat and sine my outside neck diameter is already correct , I just inside neck ream and I'm done with that part of forming. Also at the moment I do not have an inside mandrel that is the correct size to support the case neck during outside reaming. I appreciate all the replys, cuz after all I did ask a question. Do you think I could get better results( more even neck walls) by outside reaming?

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Wm Cook posted this 12 December 2022

That makes perfect sense. My hand turning is with off the shelf stuff like the pumpkin. Wouldn’t you be able to ream out the built up area and then outside neck turn. Maybe just to clean up the neck 75%? Bill.

Or is this in a tight necked chamber?

Patience isn’t a virtue, it’s a delay tactic.

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Ross Smith posted this 12 December 2022

Very tight chamber.

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RicinYakima posted this 12 December 2022

Sorry Ross, outside my experience. 

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Wm Cook posted this 12 December 2022

Ross, tight on jb’s is half a thou on each side. One thou total. How much clearance do you have factored in? What’s the +/- tolerance is on loaded cast rounds?

I’ve never worked with cast unrestricted which is where a short .308, custom reamer, custom barrel, tight neck chamber sound like it would be shot. Little envy here.

Sounds like one heck of a lot of fun. Bill

Patience isn’t a virtue, it’s a delay tactic.

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Bud Hyett posted this 12 December 2022

A reamer follows the path of least resistance, leaving a diameter the size of the reamer.This is an absolute. Outside neck-turning gives an even wall thickness with careful work.

As an example using the .308 Winchester case in a Production Class rifle, I outside neck turn using the following procedure:  

  • Anneal
  • Trim to length
  • Deburr inside and outside.
  • Resize the neck using a bushing die to a diameter .002/.003 less than .308
  • Using K&M expander, expand the inside neck diameter to .309 to allow slip-fit of neck-turning guide.
  • Turn cases to the shoulder setting for .015 wall thickness. (Note: This is the thinnest wall thickness that will last repeated firings.)
  • Check cases for minimum 75% cleanup, use cases with less than 75% for practice. 

Once setup, I process 340 cases at a time. This gives me a few spares for the cases necks that have splits in them as you progress or that split anyway in the course of a year's competition. Lots of work and sometimes I'm not sure this dedication is needed. 

Farm boy from Illinois, living in the magical Pacific Northwest

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Eutectic posted this 12 December 2022

I want to add to Bud's list which is excellent. The neck needs to be a very tight fit on the on the neck-turning mandril. You need to lubricate new cases as they will gall and deposit brass on the expander and maybe the mandril. AMHIKT! Lubricant makes a difference! Imperial sizing wax gave 0.0005 to 0.001 THINNER necks because it makes a thicker film. Graphite gave the thickest turned neck, but it is messy.

Was all this effort important? I could not see a difference between Norma brass and turned neck Norma brass. This was in a custom 308, with minimum chamber but not a "tight neck" set-up.  The Norma brass was very uniform in the turning, I trimmed some Reminton brass and saw a large difference in the amount turned off between the cases. I never did a firing comparison with the Remington brass.

I never tried a reamer die, no information.

I think the jacketed folks must have done a comparison of methods.  Too bad Precision Shooting mag is no more. 

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Wm Cook posted this 12 December 2022

I don't remember a head to head comparison of turned to un-turned brass and jb's. Seemed like all custom chambers were tight by design.  Bud gave the textbook answer for turning brass and Steve was right about using graphite. 

Neck turning to control tension has been given the kabach by others including Bottiger and more recently John Alexander in his recent article in TFS 279.  As he put it:

“Apparently, this is just something that some reloaders believe they have seen or just know is important because it sounds logical.”

I think many would agree that the only reason to turn a case is for alignment to the bore. However the accuracy improvement with neck turning is dependent upon the equipment being used isn't it.   Bud said he turns to at least 75% cleanup, discarding the outliers and he is turning neck thickness of .015.  I fully agree. This is logical, easy and even fun to do.

But a custom action, reamer, barrel will benefit more from neck turning then a production rifle.  Right?  So from the low end of the spectrum, that being a production rifle, how much is there to gain from neck turning?   I guess that last question can never be answered.  Every over the counter rifle has the potential of having a variation of bolt face to bore alignment and the degree of benefit truing up the case neck will bring.

It is possible maybe even probable that cleaning up the necks to .015 will improve accuracy.  It is also possible that the alignment is so pathetic on an over the counter rifle that even truing up the neck won't even help.

For some it just isn't going to help much is it.  For others, turning necks for production rifles even those having oversized chamber necks will put the bullet closer to the center of the bore.  For the time being I'll continue neck turning just because I think its the right thing to do.  Guess that makes me guilty of what John describes as doing someting "....because it sounds logical".

I asked a question earlier and if anyone has any reference to it I am curious what measure cast bullet shooters use for tolerance when describing a tight neck chamber. And yes I do miss the magazine Precision Shooting.  But we do have the TFS on CD.  For people like me that helps.  Thanks, Bill.

 

 

Patience isn’t a virtue, it’s a delay tactic.

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John Alexander posted this 12 December 2022

Good description Bud.  You say, "Lots of work and sometimes I'm not sure this dedication is needed. "

I also have neck turned lots of cases and have the same doubt about the value in a production chamber, or even a tight necked custom chamber for that matter since I can't remember any such testing in 20 years of Precision Shooting. The next time you do a batch why not run a quick test -  five groups each of unturned, < 75% clean up, and > 75% clean up. I wish I had done that on the last batch I turned. My present batch of match brass is going strong but I  will do the test on the next batch if I do another.

This kind of test is so easy to do when we have any doubt about extra work in reloading. And let's be honest, we do a lot of hooky things because we hope they help. Too bad we do the comparison testing so seldom.

John

 

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Ross Smith posted this 12 December 2022

Just so you all understand, I have to ream. I either use an inside reamer after sizing or I need to have a custom expander and mandrel for an outside reamer. John Ardito didn't worry about this in my opinion, he just opened up the case mouth to hold the bullet by the GC. Maybe that's all I should do too.

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Wm Cook posted this 12 December 2022

I understand the need to ream since you’re taking a 308 case down to 1.625.

How tight is the neck chambered to (in thousands) and could you tell me what the +/- loaded cartridge neck dimension will be.

If the reamer is already bought and it’s a custom tight neck I’d be hard pressed to be lucky enough to get the insides reamed neck to match up to the chambered neck. I’m just not lucky (or good enough) that way.

Sorry for straying off of the inside reaming requirement you described. Bill.

Patience isn’t a virtue, it’s a delay tactic.

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Ross Smith posted this 12 December 2022

Here's the numbers I'm dealing with.

As sized and trimmed to length:   neck OD=.338

                                                      Neck ID=.290

                                                      neck wall=.022

Fired case neck OD is .343, bullets sized to .312, chamber neck is .346. I'm open as to the best way to get to those numbers.

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Aaron posted this 12 December 2022

Holy Smoke! You need a 30-30. cool

 

With rifle in hand, I confidently go forth into the darkness.

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Wm Cook posted this 12 December 2022

So the neck is chambered to .346.  With brass neck wall thickness of .022, bullet sized to .312 it would give you a loaded round of .356 (2 x .022 + .312) which wouldn’t chamber.  But you said you have fired cases that spring back to .343 so I may have misunderstood and the neck wall is actually .011. 

If the neck wall is .011 then the loaded round would be .334 giving you .006 per side clearance or a total of .012 w/o outside turning.

My production 308 has a neck chambered at .3435.  My brass is turned to .014.  Bullet sized to .308 the total loaded round is .336 giving me .0075 side clearance.

Without being any closer than the few exchanges back and forth we’ve had, I’d look at outside skim turning the neck in the manner Bud suggested.  A custom reamer, barrel might gain from that.  A production over the counter rifle might not.  Just my opinion.

There’s a bunch of off the shelf equipment that would let you outside turn.  Or maybe I messed up my math or don’t fully understand something obvious that would prevent you from doing that. Forming .308 from 2.015 to 1.625 had to take several steps. Good luck, Bill.

 

 

Patience isn’t a virtue, it’s a delay tactic.

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Tom Acheson posted this 12 December 2022

Maybe this was mentioned earlier…..

 

Not for a “production” rifle, but for a custom chamber. Mic a loaded round. Compare that to the neck ID of the reamer/chamber. (Most gunsmiths will stamp that dimension on the side of the barrel.) The mic’ed diameter of the loaded round must be smaller the chamber neck diameter. Most people would promote a minimum clearance between the loaded round and the chamber of 0.0005” per side or .001” total. Room is needed for the brass to expand and not be constrained by the chamber during ignition. Depending on the brass thickness of the neck, outside neck turning might be needed, to produce the needed loaded round clearance. 

 

This is for rounds where not a lot of brass is removed when reducing the case length. But…..due to “brass migration” during excessive case length shortening, it might be needed to inside ream and outside turn the necks. There is no magic “always must do”. Careful dimensional examining of all involved “puzzle pieces” will be needed to determine the route to be taken that is needed. And every brand of brass does not have the same neck wall thickness.

 

My most recent adventure involved a minimal case length shortening of a Lapua 6BRmm norma case, necking the mouth diameter down to .22 caliber and then the turning of the necks down to slightly less than 0.013”. The batch of (235) cases were fired slightly under 5 times each this past match season, with no failures or problems.

 

Tom

 

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Ross Smith posted this 13 December 2022

The dimensions I gave are for a 308 case that had just been sized down to 1.625" after cutting off the excess.After inside neck reaming with a Forester case trimmer of .311 a loaded round is .343" and the fired case returns to .343. So the case neck is only expanding.0015 per side in the chamber.Is that too much? My question still is: am I better off expanding the neck so a reaming mandrel will support the case neck for outside reaming or keep on doing what I do. One answer said that out side reaming is more accurate because inside reaming follows the thin side. Should be easy enough.

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