Neck Wall Thickness Tolerance?

[Syncrowave]

For those of you who are turning necks, I'm curious how much variation in neck wall thickness you allow for before you turn.

My question is mainly toward across-the-course bolt-gun users more than benchrest guys but I'd be interested to hear all thoughts on it.

Trying to wring all the accuracy I can for long range and curious at what point neck turning is considered necessary or worthwhile.

Also, I read somewhere that the loads most guys are using in 6.5/284 are hot enough to flow enough brass to necessitate trimming / reaming / turning. Is that so? I'd be interested to hear any thoughts on that, too, since I'll be shooting 6.5/284 and am new to the cartridge as well as to this particular rifle. (Hope to use 139 gr Lapua Scenars and 107 gr Sierra MatchKings, if they'll shoot.)

Thanks in advance for any replies.

 

[jr600yd]

First ask "Why Turn Necks"? Their are three answers.
1. You have a tight necked chamber and must turn necks in order for the brass to chamber. This is common in bench rest shooting but not so much in mid-long range or across the course competition.
2. Accuracy! Now we've opened Pandora's Box. The theory is since neck thickness is the same all the way around neck tension is equal all the way around. If neck tension is not equal (fat vs thin side of the neck) the thin side of the neck will release the bullet before the thick side. This upsets the bullets concentricity with the bore. (Causes the bullet to enter the rifling a little off center). Other things come into play but this is the jest of this argument.
3. Brass Life. This may be the REAL reason for turning necks. As stated before manufactures have different dimensions for their brass. All make SAMMI specs but there is a +/- factor. Have you've ever had to use a lot of force to get a case out of a sizing die and heard the squeak as it comes out? That's because the die neck is X wide, the case neck is X thick and the expander ball is X wide. This is where most of your case stretch comes from, not shooting. By turning necks you allow a little more room, maybe .001, and the fired necks are not sized down quite as much. With your dies properly adjusted this accounts for less working of the brass and longer case life.
4. Is it worth it? If your shooting benchrest competition yes. If your shooting a factory barrel or a hunting rifle probably not. If your shooting competition under 500 - 600 yards probably not.

I don't shoot a 6.5/284 so I can't help you there. It's a very popular mid-long range cartridge.

 

[jlow]

The first thing you need to do before considering neck turning is to survey your brass. This is especially true if you are not using Lapua. What I do is to reject any case with neck inconsistency greater than 0.0015”. These will not be turned and used for plinking and perhaps for foulers. The reason is the inconsistent neck thickness tells you that the case is also not consistent as you go down the case to the head. Inconsistencies there will cause the case to “banana” when you fire it and this will cause concentricity problems. You do the survey with something like the Redding Case Neck Concentricity gauge.

The rest of the “good” brass you can consider turning for the reasons already mentioned. I used to turn and got pretty good at it but I have found that it is better to just do no turn by buying Lapua. Saves time and you end with thicker necks which I like. You may or may not be able to do no turn depending on your chamber dimentions.

 

[mikecr]

I cull cases by thickness variance, as measured at necks, before any other prep efforts. My max variance allowed here is .0005.
With this, case runout grows less over sizing cycles whether necks are turned or not.

I don't believe brass 'flows' as I've never seen it.
Hot loads mean more body sizing, which rolls the brass upward thick toward thin, with thinnest being trimmed away at the mouths. A lot of sizing means a lot of trimming with corresponding thickness change over cycles.
With improved case designs and well planned chambers, cases need less sizing, less trimming, and thickness changes and donut formation doesn't happen.

 

[bigedp51]

If you buy good quality brass, the average shooter with a stock factory made hunting rifle and scope will see very little to no advantage turning necks.

I have three five gallon buckets of once fired .223/5.56 fired by our local police departments. This ammunition was the cheaper "blasting" type ammo sold very cheaply. These cases were made up of Remington, Federal and Lake City and the Remington cases were the worst for runout and variations in case neck thickness.

You can't make a silk purse from a sows ear, bad brass will still be bad brass even after neck turning.

Cases with uneven case wall thicknesses will have more runout because the thin side of the case will expand more on firing. If fired in a military type chamber the case expansion will cause even more excessive runout and cause banana shaped cases with the base of the case not 90 degrees to the axis of the bore.

I just bought some Norma custom brass and was amazed at the quality of the brass. The Norma brass was head and shoulders above in consistency compared to my "cheaper" once fired .223/5.56 cases.

Bottom line, your chamber and brass quality will govern any improvement in accuracy by neck turning.


Life was simpler before I bought gauges, I could blame the bigger groups on drinking too much coffee, the scope or bad karma. : You can try and bend bad brass with the Hornady tool but it doesn't fix the bad brass.

I have the Redding gauge below, it tells me the average American made brass is very poor in quality, and it pays to buy higher quality brass.

 

[jlow]

Sweet tool!

 

[queen_stick]

Bigedp51,

Those pics are nice! What happens after the neck-turned case is fireformed in a concentric chamber?

 

[Lapua40X]

.... As often is the case the answer is "It depends". Different brass makers have different thickness. Lapua' .308 are 0.015 thick, Winchester 0.014 and Federal 0.016.

I use primarily Federal and have been turning necks for about 6-9 months. At first I did it wrong and turned just enough to shave off the thick parts of the neck (0.016). That did not give me good results, so I thinned down to 0.014 and that has given me very good results, now I'm finally as good or slightly better than the FGMM ammo.

I'm somewhat befuddled when I read about turning down Federal .016 necks to .014 when Winchester offers that neck thickness straight out of the box. If it's about truing up uneven neck walls, then the Lapua .015 (which is typically very consistent) might turn to .014 with higher degree of accuracy than the Federal.

 

[bigedp51]

queen_stick said: Bigedp51,

Those pics are nice! What happens after the neck-turned case is fireformed in a concentric chamber?

+1

If the case has uneven case wall thickness the thin side expands more when fired and the case "springs back" with excess run out. It doesn't matter if you have a concentric chamber when your cases are warped and bent out of shape when fired.

I collected milsurp rifles and they have a larger diameter and longer headspace chamber settings than factory rifles. If you have uneven case wall thickness the fired cases will always produce LARGER groups than when new brass is first fired. You can't fix a warped banana shaped case, and they are only good for suppressive covering fire in Zombie attacks.

When your brass is that bad its time to fix bayonets and yell charge. (Enfield American/Australian humor)

NOTICE: No Koala bears were hurt or injured during the filming of this posting. :

 

[bigedp51]

That's too funny!!!!!

What isn't funny is spinning so many cases checking run out you wear the paint off the V-blocks and wear away the aluminum. My next buy will be the Sinclair Concentricity Gauge gauge with "HARD" steel ball bearings.

 

[bigedp51]

What isn't funny is spinning so many cases checking run out you wear the paint off the V-blocks and wear away the aluminum. My next buy will be the Sinclair Concentricity Gauge gauge with "HARD" steel ball bearings.

Look at reply #6

Sorry, I'm a cheap bastard, I use a pink eraser as my rolling device and not have to pay for the fancy rubber wheel.

Besides my Finance Minister has to approve anything over $100.00, "WE" are saving for a European river cruise and the wife doesn't care if I "run out" of money. :'(

 

[jlow]

Lapua40X said: I'm somewhat befuddled when I read about turning down Federal .016 necks to .014 when Winchester offers that neck thickness straight out of the box. If it's about truing up uneven neck walls, then the Lapua .015 (which is typically very consistent) might turn to .014 with higher degree of accuracy than the Federal.

You're absolutely correct. But I didn't buy the Federal brass, I got a couple thousands of cases after firing FGGM 168 grain ammo. If I was starting with virgin brass I would probably start with Winchester.

As a side note, I did a little comparison test, 20 virgin Lapua cases with no neck turn, 20 once fired Winchester cases with no neck turn and 20 Federal cases with neck turned. I sized and loaded them the same way. I was shocked to find out that the Lapua were the worse of the 3. I bought 200 cases expecting to eventually transition to them, but now it's far from a foregone conclusion. When I use up my Federal the Lapua's are going to have to prove their worth to me through some re-testing.

A couple of things. One is I for one will not spend any time neck turning Federal 308 cases. The general opinion is that they are soft and their primer pocket will be loose after one extra firing.

The second thing is when you say “shocked to find out that the Lapua were the worst of the 3”, what exactly were you measuring?

 

[Bob3700]

I too am somewhat new to the 6.5x284 and have not shot a bbl out yet. Only have about 500 rds down the tube. But here is what I have found.

My chamber was cut with a no-turn neck (.2975") for Lapua brass. I have about 450 pieces of brass for this cartridge and have found that I can measure the necks and they are not all that bad. Once I FL resize the brass, my last step is to run the necks over a mandrel that makes the ID of the neck uniform, the mandrel also establishes my neck tension. The mandrel makes my neck tension consistent. I have shot the 139 Lapuas and they are not bad but have found in my bbl the 142 SMKs are a bit better.

My personal preference is to load for best accuracy not max FPS. That said, my bbl shoots best between 2950 and 3020FPS. Not a max loading by any means. There is a lot of boiler room in a 6.5x284 and the bullets have a "Sweet Spot" velocity wise. Don't get caught up in a drag race. BBL life is short enough as it is.

I strictly shoot this rifle in 1K HP Prone competitions (Iron sights with sling).

308 - I have a good supply of 308 that I shoot in a Palma rifle. Use the same mandrel approach as the 6.5. Have not turned a neck yet and it will shoot better than I can hold. Have used the Lapua Palma brass (small primer pockets) and it is right there with the best brass I have. Only sort brass by wt. I bought some of the old Federal nickeled match brass years ago and it was excellent. The newer FGGM does seem to lose primer pockets faster than the Winchester or Lapus brass. I shoot mainly 155 gr SMKs in my 308 so that may or may not be an apples to apples comparison against the bullets you are shooting.

HTHs

Bob

 

[jlow]

Lapua40X said: what exactly were you measuring?

Five shot groups at 100 yards. It's far from conclusive because I was using Redding National Competition die and it has no bushings to adjust for the different neck thickness. It really wasn't a good test. I've learned a few more things since. I didn't mean to start a war, given your username I assume you're a die hard Lapua customer.

No war intended, just wanted to make sure I know what your conclusions were based on. I have no loyalties to Lapua, so far, they make great stuff and I use them.

It is just that you came across so conclusively and yes 5 shot group at 100 yards means very little. First , the group number is small but really there are so many other things in your reloading (apart from the brass) and shooting that can affect this that you really cannot conclude anything with this data.

 

[treeman]

apparently he didn't need his willy any way

 

[Martin52]

For those of you who are turning necks, I'm curious how much variation in neck wall thickness you allow for before you turn.

For long range accuracy, i don't support any variation if I can eliminate it, or, as below, at least reduce it to the minimum I can get using the tools I have without making the case neck too thin.

I turn all my brass, even though I find the variation in new Lapua brass quite low, however, it does depend upon the lot so I just turn all my brass, just part of my standard process. New, the variance may be 0.001.

I turn new .308 brass to 0.014, it's usually about 0.015 out of the box. The variation in neck wall thickness after turning (I use K&M mandrel and turn by hand) is less than 0.0002. I have to get down to 0.0140 before I can reduce the variance down to that level.

 

[Syncrowave]

This is all great information, and I'm learning a lot. Thank you all for your replies.

 

[Syncrowave]

Thanks, Joe, I'm shooting 6.5/284 but I suspect Erik knows about that too.

 

[Dave M.]

That's what all of us are trying to do. Regardless of whether you're shooting benchrest, F-TR, XTC, etc..

I remember watching reloading videos by David Tubb, AGI and others and thinking: Neck turning??? Concentricity gauges??? Measuring each powder drop??? Annealing??? These guys are CRAZY." A couple of years later I'm doing all of those things. Why?? That's what you have to do if you want "Accuracy".

Having said that, my experience is that if you reload and want accuracy sooner or later a REALLY good concentricity tool is ESSENTIAL. I tried a Sinclair and a Necos, but I found them slow and a bit frustrating to work with. Then I found the CTK gauge

and decided to give it a try. Its expensive but it has turned to be well spent money for me. I highly recommend it. I use it as diagnostic tool to see if something is out of alignment at each step of the process so that by the time I seat a bullet everything is fixed and the only thing left is seating. I was amazed on how I could fine tune the seating of my dies so tat I can get CONSISTENTLY good ammo. You know how frustrating it is getting to the end only to find out that half or more of your reloads aren't going to do the job. This is true regardless of which brass you end up using.

It was the concentricity gauge that made it irrefutable that I had to turn necks. When you spin it inside the neck and outside the neck the answer is obvious.

Concentricity gages gather dust on my reloading bench. Virtually meaningless based on my, and many other shooters testing.

 

[Bronsin]

Mine sit on the shelf too, but only after I have confirmed my die setup produces loaded rounds with minimal runout consistently.