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Case Head Seperation and Brass Growth at Resizing

 
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  #1  
Old 02-28-2013, 03:07 AM
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Case Head Seperation and Brass Growth at Resizing

Okay guys, here's a poser for you. I've got a Remington 700 Mountain Rifle in 280 Remington. I've started trying to work up a load for the Berger 168 gr. VLD. When I started, I found some Federal brass in my inventory. I've had this gun for a long time. It was one of the first batch of stainless Mtn. Rifles Remington made. So the brass is of unknown origin. But I full length re-sized it since that's the only die set I have for a 280, so I figured it wouldn't matter. I took 12 pieces of brass and loaded four different loads and test fired them. Before the next loading, I trimmed the cases to 2.530". I had to remove about .020"-.030". I reloaded them again with different loads and test fired them again. On the third re-sizing I noticed one case had a partial case head separation. I checked the remaining 11 cases and found that they were getting ready to separate also. I felt the thin area with a hooked wire and could see it with a flashlight. I trashed the cases. There were about 30 more pieces of brass in the MTM box so as a precaution, I checked them too. They also had thin spots so I threw them away too.

Okay, so now I'm wondering if the brass was fired in my rifle originally and if so, did my rifle have a problem. I checked 10 Remington brass on hand and it was okay. The only other brass I have is Nickle in both Federal and Winchester. This brass checked okay also. I think it was fired in my rifle but not positive. I have 4 empty nickle cases from factory Winchester loads that I fired last weekend to sight the rifle in that I know are once-fired in my gun. I started taking measurements to see if I can find the problem, if there is one.

The new un-fired Winchester brass measures 2.531" base-to-mouth and 2.163" base-to-shoulder. A fired case measures 2.534" base-to-mouth" and 2.169" base-to-shoulder. Nothing too bad. The case length grew .003" and the shoulder moved forward .006".

Okay, now is where my questions come in. I re-sized one of the fired cases in a Lyman full length sizing die with a carbide expander button, lubricated with Imperial sizing die wax. I measure the sized case. The base-to-shoulder length is now 2.159", .004" shorter than factory. Maybe a problem since the next firing will be .010" growth at the shoulder. Next I measure the re-sized case length and its now 3.554". The case has grown .020" in length from being sized one time.

Here's my questions: Are any of those measurements out of line and could they be the reason the cases separated?

Let me add that the brass just below the shoulder expanded .008" and the brass seemed hard to re-size on my Rock Chucker IV press. Any thoughts or suggestions?
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Old 02-28-2013, 06:39 AM
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Re: Case Head Seperation and Brass Growth at Resizing

Chambers can vary in length and still be within the SAMMI specifications.

I believe you are oversizing your brass. The full length sizing die doesn't have to be fully bottomed out against the shell holder to properly resize once fired brass. You only need to size the brass enough to fit the chamber and reduce the neck diameter to hold a bullet. If brass is over sized and fired, over time this will cause excessive brass flow lengthening the brass which requires frequent trimming. More importantly the brass is thinning down just in front of the web which will cause case separation as you experienced.

It is best to use new brass in your rifle and keep it segregated by number of firings. If you follow the steps below your brass should last much longer and you will avoid the case separation issue.

Adjust your FL die so there is a space of approx 1/8" between the shell holder and the end of the die. Size a case, wipe it off and try it in the rifle's chamber. It will most likely be snug. Turn die downwards 1/4 turn or so and try again. At some point during this process the brass may get harder to chamber. Continue adjusting the die downwards till the brass fit easily. Fine tune the adjustment by raising it slightly and try again till you get the bolt closure feel that suits your needs. (some folks like a slight resistance) The goal for most hunters is to not have any resistance when cycling a bolt for a speedy second shot.

Once you find the setting you can tighten the lock ring setscrew for repeat setup in the future. I prefer to use feeler gauges to measure the gap and put those gauges in the die box.

Hope this helps.
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Old 02-28-2013, 10:25 AM
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Re: Case Head Seperation and Brass Growth at Resizing

AZShooter
I appreciate the response. I agree with everything you said. What you prescribed is pretty much the procedure I use for reloading. If possible I try to use a neck sizing die for most reloading. Occasionally though, you have to set the shoulder back to get your cases to chamber. I like the Redding graduated shell holder sets that let you find the correct amount of re-sizing for your chamber. I have the correct set for the 280, I just never got to the point that I thought I needed it. I didn't know the history of the brass. What made me wonder is that I've never seen a case grow .030" on one sizing. That and I didn't know how much a FL die should set the shoulder back. I'm wondering if my chamber is over sized or if my die is undersized.

I'm headed to the reloading store today to see if I can find some new brass and a new set of dies. I've got several boxes of factory ammo, but it's 3-4 different brands. I need maybe 50 or 100 new brass to set this gun up for reloading the new Berger load.
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Old 02-28-2013, 06:00 PM
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Re: Case Head Seperation and Brass Growth at Resizing

Like AZ said, you are oversizing

Typically a case shoulder will move ~85% toward being in contact with the chamber shoulder on the first firing. Then it will take additional firings to where it will contact the shoulder and cause a crush fit

For example here is a typical string of measurements on a 30-06 with close to max loads where I neck sized only until I got the crush fit (the measurements themselves don't matter, just their relationship to each other), measurements taken with a Hornady comparator attached to calipers

New case - 2.040"
Once fired - 2.0485" (neck sized only with Lee Collet)
Twice fired - 2.050" (neck sized only with Lee Collet)
3 times fired - 2.051" (slight crush fit, still neck sized only with Lee Collet)
4 times fired - 2.0515" (crush fit, neck sized Lee Collet, shoulder pushed back Redding Body Die)

After the crush fit you need to push the shoulder back only .001" or so. That will give you a very slight crush fit and keep your brass from overexpanding each firing and being overworked.

If you are pushing once fired brass shoulders back .010" then you probably have headspace on those sized cases of .012" or so, and that is waaay too much. Case head separations are predictable with that practice.
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Old 02-28-2013, 11:40 PM
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Re: Case Head Seperation and Brass Growth at Resizing

Okay, I bought a set of RCBS full length dies. When I got home I fired two factory rounds through the 280 Remington and took some measurements. I also bought one of the Hornady Lock-N-Load Cartridge Headspace Gauge Kits. The case grew .002" when it was fired. The RCBS FL die pushed the shoulder back .005". The Lyman FL die pushed the shoulder back .010". I think I found my problem. The Lyman die was short. Will put them in the no-longer-used box.

I will use the Redding Competition Shellholder Set to set the die to only set the shoulder back .001" when the die touches the shellholder. This will be the +.004" shellholder. I tried this on one of the fired factory loads and it looked good.

No luck finding 280 brass at my gun shop so I guess I'll have to order it online along with a neck sizing die. Thanks for the help. Still looking for pet loads for the 280 with the Berger 168 gr. VLD.
Nimrodmar10.
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Old 03-01-2013, 11:35 AM
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Re: Case Head Seperation and Brass Growth at Resizing

Quote:
Originally Posted by Nimrodmar10 View Post
Okay, I bought a set of RCBS full length dies. When I got home I fired two factory rounds through the 280 Remington and took some measurements. I also bought one of the Hornady Lock-N-Load Cartridge Headspace Gauge Kits. The case grew .002" when it was fired. The RCBS FL die pushed the shoulder back .005". The Lyman FL die pushed the shoulder back .010". I think I found my problem. The Lyman die was short. Will put them in the no-longer-used box.

I will use the Redding Competition Shellholder Set to set the die to only set the shoulder back .001" when the die touches the shellholder. This will be the +.004" shellholder. I tried this on one of the fired factory loads and it looked good.

No luck finding 280 brass at my gun shop so I guess I'll have to order it online along with a neck sizing die. Thanks for the help. Still looking for pet loads for the 280 with the Berger 168 gr. VLD.
Nimrodmar10.
Perhaps I am reading this wrong but it sounds like you are just setting the die according to the instructions where it is threaded down to hit the shellholder. This is not necessarily correct. If the RCBS die is pushing the shoulder back .005" then it is adjusted wrong also. It should be set to push the shoulder back .001" AFTER THE CASE HAS REACHED A CRUSH FIT IN YOUR CHAMBER FROM FIREFORMING.

When you say

"set the die to only set the shoulder back .001" when the die TOUCHES THE SHELLHOLDER"

it should be

"set the die to only set the shoulder back .001" FROM THE FIREFORMED MEASUREMENT"

this might be when the die has not been threaded down far enough to hit the shellholder or it has. What is important is that you set your die for your individual circumstances.

If I am misreading or misunderstanding, my apologies
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Old 03-01-2013, 02:42 PM
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Re: Case Head Seperation and Brass Growth at Resizing

Quote:
Originally Posted by woods View Post
When you say

"set the die to only set the shoulder back .001" when the die TOUCHES THE SHELLHOLDER"

it should be

"set the die to only set the shoulder back .001" FROM THE FIREFORMED MEASUREMENT"

this might be when the die has not been threaded down far enough to hit the shellholder or it has. What is important is that you set your die for your individual circumstances.

If I am misreading or misunderstanding, my apologies
Sorry , maybe I didn't explain well enough. I'm using a set of Redding Competition Shell holders. There are five of them , each made .002" taller than the last, which allows you to select the one that resizes the case to whatever amount you want and still screw the die down to the shellholder. This makes it easily and accurately repeatable. In my case , I'm using the +.004" (.005"-.004"=.001") to set the die to resize my cases the least amount that will still chamber.
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