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Neck turning - How much is too much?

 
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  #1  
Old 02-02-2012, 10:15 PM
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Neck turning - How much is too much?

When one turns a case neck, what would the "minimum" allowable thickness be?

I have a box of 50, once fired brass that has neck wall thickness' between .010" at the thinnest and .014" at the thickest in each case. (measured with a Redding Case Gauge) The whole lot is fairly similar. If I turn these necks to something like .0105" to .011, will the neck wall be too thin to be safe? If this is acceptable, how thin could one turn the neck and not have a problem right off the bat?

The rifle chamber is SAMMI standard. It's not a custom chamber.

Thanks
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Old 02-03-2012, 07:14 AM
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Re: Neck turning - How much is too much?

You have stated some of the details but not enough to give a good answer. What chambering is this?
Is this unturned once fired brass?


There has to be some space between the chamber neck and the loaded ammo for bullet release. Factory chamber necks are usually quite large to accomodate a variety of ammo and situations.

If your rifle is a custom you can order a custom reamer and specify the chamber neck dimension and turn necks accordingly or request a no turn neck. If it is a hunting rifle I would research what others are doing. Generally most hunting rifles with custom made chambers will be using a total clearance of at least .004" or more.

If the gap is too large the necks will be over worked expanding to fit the chamber neck upon firing then be sized back to a useable dimension for gripping the bullet. Neck cracks will show early in the brass's life.



I have a 30 BR that has a .332" diameter chamber neck. The brass has been turned to .011". This leaves a .001" clearance on each side of the cartridge for bullet release. This is generally the smallest dimension that a BR shooter will go. This requires using steel wool on the necks after firing before resizing. If any soot would be allowed to accumulate it could tighten up the small gap between the case wall and the chamber causing high pressure. This is unpractical for any sort of LR hunting rig.

Give us some more details and we can get more specific.
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Old 02-03-2012, 09:36 AM
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Re: Neck turning - How much is too much?

My fault. I'm too wrapped up in one detail and got lost with everything else.

The rifle/ chamber in the immediate question is a "from the factory" Remington 700 .223 with about 800 to 1000 rounds through it. The only "smithin" done to the gun has been a trigger replacement. The gun will shoot some factory ammo to just under 1 MOA at 150Y and some of my reloads have shot 5 round groups to under 1/2 MOA. Later on I'll be looking at another 700 with a SAMMI spec'd barrel from Hart in 7mm Rem Mag. I'll look at this gun another time.

The .223 brass in question is 1x fired factory ammo from Remington - qty 50.
At this moment, the brass has been decapped with a decap die (not a sizing die), ultrasonic cleaned, primer pocket brushed clean, flash hole reamed with a Lyman flash hole tool. they were then Body sized with a Redding body Die and the shoulder moved back .002 to .0025 measured with an accurate Starret dial caliper and Hornady headspace gauge. The necks wall thickness' were then measured with a Redding Neck Gauge to see if any cases were perfectly concentric. None have a runout of less than one and one half thousandth of an inch. Most have runout between two thousandths to four thousandths of an inch. Four cases are over four thousandths and have been marked and isolated. I'll use them for fouling shots or the like.

As mentioned before, the neck wall thickness' range from .010 to .014+" the really bad cases were the thinnest.

The next steps anticipated are trim to length, deburr & chamfer. I'm waiting for a chamber length plug from Sinclair to determine the actual length of the chamber before cutting the cases. Then neck sizing before turning the necks before cleaning again. The last step to complete case prep will be to measure case concentricity.

The goal, if possible, is to create a batch af cases that are as concentric and identical as possible considering the stock. Then to explore what improves accuracy, and of course what shouldn't be done. If they are turned too thin and don't last but a few firings that will be OK. When I get an idea of what the rifle likes to shoot then I'll get some good brass and continue to squeeze every last bit of accuracy from the gun. I just don't want to damage the gun or myself for that matter, in the process.

Above, I've given the details I know at the moment. Is there anything else one would need to know? If so, I'll measure or whatever when I get home tonight.

Thanks again for the help

PS AS I'm writing this, I'm thinking about what you have already mentioned and I'm thinking I should have a chamber cast made in this gun or will a carefully handled fired case give me a sufficiently accurate diameter?
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Old 02-03-2012, 09:56 AM
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Re: Neck turning - How much is too much?

Go ahead and turn the necks all the same if you like. They may crack on the first firing. Bottom line is you are going to shoot poor brass in a factory chamber to see if you can get your handloads to shoot more accurately. The only gain you might get is a more consistent neck release.

If some necks are .014" and others .010" the cases are most likely thicker elsewhere. This will mean the internal dimensions will be different. That difference might negate any tiny gains you might see with consistent bullet tension.

I would suggest you read the information from 6mmBR.com
223 Rem + 223 AI Cartridge Guide

I suggest you scrap your idea of tweaking the rem brass and buy some Lapua brass. To quote the article I linked:
"To achieve high levels of accuracy in the .223 Rem, you need quality brass. Among the dozens of .223 Rem/5.56x45 brass makers, Lapua produces the highest quality and most uniform brass we have found. If you look at the charts, new lots of Lapua .223 brass showed the smallest extreme spread in weight among all brands..."
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Old 02-03-2012, 12:42 PM
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Re: Neck turning - How much is too much?

I ordered some Lapua brass. Should be here next week sometime.

I'm going to turn a dozen of the Remington cases just to see how well they shoot with a moderate load and to take some measurements - I'm curious. 6 turned to clean 50% and 6 turned to clean up 90%.

The rest will be delegated to the AR15 as is - just resize.

Thanks again
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