Brass Lengthening in FL Sizing Die

[3498D]

All,
I am having a frustrating issue reloading and was hoping someone here could give me a little help.

Right now I am doing load development and barrel break in for a new rifle, and have fired my first 100 pieces of Lapua brass once.
After decapping and tumbling them, I'm running into issues resizing.

I'm trying to full length resize and bump my shoulder back ~.002", which seems simple enough.
My resizing die is a Redding S series, full length sizer. It has a neck bushing and the mandrel is removed.

After resizing, cases are consistently measuring .004-.005" LONGER than when they started, which seems impossible.
This is measured on a set of Starrett calipers that I know to be accurate, using a shoulder bump gauge that measures at mid shoulder - not OACL.

My press is a Forster Coax, and the die is as far down as is physically possible while still being able to cam over the press; it takes some noticeable effort. I can't lower it any further.

The die is also leaving a weird ring or distortion about mid-shoulder on the resized cases, which is easier to see in person but I did include a photo.

Needless to say this is perplexing. I feel like my dies, press, and method are 'good', and my measuring devices are telling me the truth, I just cannot see how this is occurring.
The resized cases will chamber, which also seems strange.

First photo is 1x fired, untrimmed brass - just decapped and cleaned. 2nd is after resizing, 3rd is the distortion the die is leaving on the shoulder.

**I am not using WD40 as lube, the can is just in the background. Imperial sizing wax, used as directed.

 

[Bill Norris]

After resizing, cases are consistently measuring .004-.005" LONGER than when they started, which seems impossible.
This is measured on a set of Starrett calipers that I know to be accurate, using a shoulder bump gauge that measures at mid shoulder - not OACL.

If the case is not going far enough into the die the brass will elongate to some degree. Check to see if the die is screwed down far enough into the press.

 

[L1986]

can you tell us a little about the gun..if the case that is 4thou longer will chamber freely then you might not need to push the shoulder all the way back. It could be that the virgin brass was very short and it may take more then one firing to get them long enough to need the shoulders set back. You really need to figure out how long your chamber is before you set a measurement to push the shoulders too.

 

[Walt Krafft]

What cartridge?
Back the die off a full turn and size a case. Check it in the rifle. Turn the die in a little at a time until the brass fits the rifle.

 

[JFrank]

Q- will 1x fired cycle freely ? If so ..stop sizing, Put those calipers away until the case resist’s cycling through the weapon, then follow Walt’s post.

 

[L.Sherm]

Watch Alex's video on the stripped bolt method.

 

[243winxb]

Where is F. Guffey with his feeler gauge?

Start with .005" gap between shell holder and die. Fire, size again. If bolt hard to close, adjust die down.

Shell Holder Adapter

 

[jepp2]

cases are consistently measuring .004-.005" LONGER than when they started, which seems impossible.

That is what happens when you size brass before the shoulder contacts the die.

 

[CharlieNC]

I had that issue one time when shooting new brass in a new chamber, and after the initial sizing did not occur after subsequent firings. Seemed the angle of the chamber shoulder was different than others, which is what jepp2 is showing. Trim and see if it happens again.

 

[Coyotefurharvester]

As always, if fired brass will chamber with minimal bolt effort, don't push back the shoulders. Lube the neck, no lube on the shoulder, lube on the case body. Shoulder dents or distortion usually indicates too much neck lube. Die need to be clean, debris free especially with wax based lube. Set die so brass will chamber properly. If I I have brass that has more than 0.004 bolt face(bolt gun) clearance after first firing, I will set the die out slightly further than a zero shoulder movement setting. As a 0.001-0.002 length increase will not affect function.

 

[spclark]

This is why case trimmers exist; brass cases can / will stretch during firing, this becomes apparent when resized using proper procedures and equipment.

Knowing where your case mouths end and where your rifle's case neck chamber bore ends is important. Best to to avoid having cases get too close to the beginning of the small bore's diameter meant to receive a bullet. Otherwise pressures upon ignition can rise quickly when case neck can't expand as intended.

 

[M-61]

I'm trying to full length resize and bump my shoulder back ~.002", which seems simple enough.

Why were you bumping the shoulder? Failure or difficulty closing bolt?

 

[6.5 forever]

You must be using a mandrel. Make sure the brass length is measured AFTER using the mandrel. The length shrinks several thou after the mandrel. I can't see anything in the picture to worry about.

 

[boltfluter]

Depending on your load cases may not be fully formed to the chamber for 3 firings or so. You could put some cellophane tape on the back of a case to see how your case shoulder matches up to the chamber. 1 layer of tape is usually. 002 thick. Add layers until it is hard to chamber and you have the approximate clearance. Adjust your die when the first case , from continued firing, chambers with resistance. Good luck and keep us posted.
Paul

 

[dellet]

With new brass, maybe more so in a new to you chamber, you should have 3 measurements.
New out of the box
After being fired
After sizing.

If the base to shoulder lengthens after firing, the brass has not grown enough to fit the die. The question will be if it has grown enough to fit the chamber. Easy enough to check.

The reason it grows in length was shown in the earlier post. #8.

What that diagram does not show is what happens when a shoulder is not completely formed and probably what you are seeing on your brass. The case was not long enough base to shoulder to contact the die. It has to be blown out, before the die can set it back. Next firing should do that.

Zeroing the caliper is nice to check movement. But it does not have any meaning when solving a potential problem. Your fired brass could perfectly fit your chamber, and your die or shell holder could be the problem. Could also be a chamber issue. You need to compare your brass to actual or expected chamber size.

Measuring the brass new out of the box, should give you an idea of how much it needs to grow.

Easy to explain what happened while sizing, with the other reference points, impossible to say if it’s good bad or even possibly dangerous.

 

[Doom]

@jepp2 post shows what happens when full length sizing brass. It will grow on every sizing even if the shoulder has grown fully to the chamber. The issue is the increase in the body diameter on firing along with the shoulder being reformed to fill the chamber. In resizing the body diameter is reduced which pushes the shoulder forward and then the die reforms the shoulder lower on the case. The extra brass moves to the neck. The closer the fired body diameter is to the resized diameter the less the brass will grow.

 

[K22]

Lots of excellent advice on the sizing aspect of your problem, especially posts 8, 12, and 15, so I won't repeat.

Is the "ring" on the shoulder surface (scratch) only or an actual indentation? Is just a surface mark it could be from a sharp edge of your bump gauge insert. I have seen this before and it is merely cosmetic.

However, if it is a true indentation (i.e., deformation) of the shoulder then this requires investigation and resolution. It would appear something is amiss during sizing. I have no experience with "S" dies or bushings so I cannot offer any plausible reason why sizing would cause this condition. Perhaps others with experience using these sizing dies can offer something. But a deformation of the shoulder is not something that should be ignored.

 

[jelenko]

Hmmm. It's not clear to me whether the OP is concerned about change in headspace or case overall length.

If the concern is that the case overall length is getting longer, that's natural - always happens with full length sizing.

If the headspace is changing, does that mean that there is less headspace after resizing? I.e., instead of bumping the shoulder back, it's being drawn out?

 

[JMayo]

I find "pull back" feeling when raising the press handle makes mine grow.
Anytime i don't lube enough in the right spots i can feel it. I start picking up my cases near the base and work my fingers up to the case mouth spreading the lube more.

I resize out of a tray ive sprayed with one shot (black can)

 

[TTE]

Guys .... he said he was using a Co/Ax press. Can't screw the die in any farther than to the universal shell holder. Well, a bit more, but no where near a 1/2 turn.

Other than that ... good advise above.