New Neck Die, found new issue??

[Wile E Coyote]

My question today is based on my observation (more like a revelation ) concerning neck thickness diminishing as cases get sized, fired and resized. Below is a brief outline of what I have in brass and have done which leads me to the questions; Is this normal and will this change be reduced with my new dies? Is there something I should try to do differently? Or is there a step I should eliminate or add to my process?

A few days ago, I purchased a new set of dies to use specifically for my .223 Rem 700 VSSF II with the original barrel with about 950 rounds through. The dies are Redding S type with the Comp Seater. I also bought several bushings based on 3 batches of brass I have; a .250, .248, .246, and a .244. This was my jump off point knowing I could get the in-between sizes or greater/lesser sizes in the future. As for the brass I have:

#1 batch is new in the box Hornady unfired- un-turned (100 pc), new brass has necks with consistant thickness/runout between .0145" and .0155".

#2 batch is Hornady with 2 firings (100 pc from the same batch as above) and was turned after the first firing. From my notes, after turning, the necks were 0.014". Now after the second firing, they are .0125 to .0135" They are cleaned but otherwise need to be reworked before loading

#3 batch is Winchester (100 pc) - turned after 1 firing and now have 6 firings. These necks started at .014 after turning and last night, they range between .011 and .0125. This brass is also cleaned but otherwise un-prepped for loading.
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Up until last night, all resizing was done with a Hornady full size die set to move the shoulder .0025" This die is also used for my AR15 where I use different brass and brass retired from the 700.

None of the brass has been annealed. I'll get into this someday soon I'm sure, just not today. After each FL sizing they were also trimmed and deburred to 1.750".

Last night, I set up the new body die on 10 pc of Winchester brass to bump the shoulder exactly .0015". The new neck die was set-up to size 90% of the neck using the .244 bushing and the cases chamber perfectly.

Are my observations normal? How far could I let the neck thickness diminish to before they should be tossed in the scrap pail?

Thanks in advance for any and all replys.

 

[boomtube]

"How far could I let the neck thickness diminish to before they should be tossed in the scrap pail? "

Not real sure I understand the premise of your question. IF you're thinking necks 'wear' thinner as we use them, that's not true.

 

[Wile E Coyote]

I'm not thinking they Wear as in abrasion. But rather "pressed" as a function of firing the cartridge in the chamber and the brass gets thinner and/or when the brass was FL sized . Perhaps when the expander ball passes through the neck it stretched thin.

I'm just trying to understand what is happening.

One other thing to note if this helps one to understand this problem, most of my loads have been at or near the MAX shown in the Hodgdon manual. A few had slightly flattened primers when testing and those were the loads that are reduced but just to the point where primers were not flattened.

 

[Innovative]

Wile ......

You've probably noticed that brass stretches as it is reloaded ad fired over and over. Cases need to be trimmed to length, but case necks don't get thinner. In fact, they usually get thicker as brass migrates from the shoulder.

This isn't a problem unless you have a custom tight neck chamber. If you measure different brands of brass (at the neck), you'll find that the neck thickness varies quite a lot. You can easily measure the difference with calipers by measuring the neck diameter of loaded rounds.

 

[Wile E Coyote]

The rifle is "as shipped" from Remington in 2009 except for the trigger and firing pin were replaced with aftermarket components. The barrel was also firelapped early on - made a significant difference.

Larry, yes I have noticed the brass stretching in length. After the first firing or two and sizing those cases (lot 3) were at or over 1.760" using the fixed size of the Hornady die. I recall trying some of those cases in the chamber (before trimming to length and loading) and the bolt would not close properly. After trimming, the bolt closed normally.

Next time I get a chance to work in the shop, I'm going to take a half dozen new cases and select the bushing based on: (.224 bullet dia. + (neck wall thickness x 2) - .001) to find the "ideal" bushing diameter. Then I'll use the closest bushing I have but no more than .002 tighter to size the new cases and load. Then on the weekend, time permitting, I'll take these six through 6 or 7 cycles of loading -firing- repeat. Each time I'll carefully measure the necks and trim, then recompute the bushing size and reload. Then and chart how the necks change.

Depending on what changes I see, I'll probably reallocate my lot 3 brass for use in the AR15 and stick with the new brass in this rifle. I think I may be overly concerned because I never measured the diameters, except when turning necks, because with the fixed die these diameters were a given.

Thanks again larry and boom