0.03" growth after first fire (264WM WW Brass)

[Mram10us]

I appreciate the comment about setting a false shoulder for fireforming. Has anyone upsized 7mm virgin brass to .30 then neck sizing down with 7mm to create the false shoulder..lots of work and annealing. Not advising, just curious.

I have made pins (act as mandrels) for expanding necks. No need to go more than .005" or so, assuming you get that pinch. Never tried just expanding the very end of the case mouth enough to get a pinch..... might be worth a try. No need to expand the entire neck just to resize it back down

 

[Mram10us]

True. But if you have any gauges (go, no-go, etc.), you can measure them with your Hornady comparitor and determine the offset.

When you measure your fired brass, apply the offset. Voila - now you can properly compare to SAAMI.

When i started making my own go gauges, i did that to verify they were correct.

 

[P7M13]

This is some ancient stuff, purchased at an auction by my mom's boyfriend 20 years ago (who knows when it was manufactured before that),

C'mon! Every man knows, "stuff shrinks with age and still works."

 

[cajun]

Yes you can use bolt closing feel to set your die. But what about a single shot or semi auto? I load for those too. Besides trying to feel a couple thousandths is pure guesswork. The hornady tool costs 40 bucks. Over sizing brass is not just a belted case concern. So for the price of one box of bullets you can know how much you are sizing your brass. There is no reason not to have one.

 

[ThrdKllr]

I have made pins (act as mandrels) for expanding necks. No need to go more than .005" or so, assuming you get that pinch. Never tried just expanding the very end of the case mouth enough to get a pinch..... might be worth a try. No need to expand the entire neck just to resize it back down

You would have to expand it at the shoulder to hold the case back. If expanded at the mouth of the neck it wouldn't hold the bullet.

 

[Mike Matteson]

I appreciate the comment about setting a false shoulder for fireforming. Has anyone upsized 7mm virgin brass to .30 then neck sizing down with 7mm to create the false shoulder..lots of work and annealing. Not advising, just curious.

I don't understand why you would size up then down? Changing a caliber of one case to another is away to create the cases you need or wanting to reload. There time like present time now that brass can be a hard thing to come by. So knowing what you can convert one case to another is important. A lot of time I can get a buy on cases in one caliber or another. I purchase them and convert them to another. Sometime I find brass that has been fire laying on the ground that somebody has left. I pick it up and save it for a rainy day if needed. There more work when doing that, but. I watch for sales to cut my cost down to reload. Like Hazmat charges getting several different powders if possible at one time

And this thread illustrates why belted cases suck.
I got rid of all mine after dealing with case head separation in 3 firings

I never had that problem in 3 firing with a belted mag. I have had head separation in any case that I reload for. That's why you have to check all cases. Especially after 3rd firing and from any then on. If you pickup other cases from the ground, and you don't know anything about them, that the first thing you need to do check case separation.
.

 

[nmbarta]

I understand that. The point i am getting at is, if you get a case head separation due to oversizing the brass (pushing the shoulder back to far), you should get it when firing brass that is .030" short. The only remedy is false shoulder or jamming a bullet like BG referenced. I have not seen any belted mag cases even .020" short of saami, but maybe I'm lucky. That is why I questioned his headspace.

I see what you mean, it's certainly possible that his head space is off.

 

[nmbarta]

Maybe a little off topic. Don't have a comparator or fancy die set-ups. What is the best way to set belted case resizing die? Here is what I do so tell me if I shouldn't be doing this. Hornaday custom grade dies - case once fired and annealed, run shell holder up until it contacts die at top of stroke then back die off 1/4 turn and size case. Cycle in rifle, if bolt will not lock then slightly screw down die until bolt locks with slight resistance on bottom third of of lock stroke. Sig brass with about 7 firings with a few hot loads during testing and not aware of any signs of case separation.

This is better than fl sizing, but it's not ideal. I'll try to find an old post that gives you the math on it so I don't have to type it all out again.

 

[nmbarta]

I'm sure most of you have this, but for those that don't.

14 threads per inch on your sizing die
1.000/14= .0714 per turn
.0714/360 degrees=.00019 (.0002 for this)
.0002x10=.002
10 degrees is about .002
360/10=36
1 36th of a turn = .002
.0714/8=.0089 1/8 turn=.009 as mentioned.

There are some slight variables here but it'll get you pretty close.

handy stuff

As you can see, it's tough to do this without proper measuring tools.

 

[Mram10us]

You would have to expand it at the shoulder to hold the case back. If expanded at the mouth of the neck it wouldn't hold the bullet.

I would disagree , good sir The goal is to keep the base of the case against the boltface during the firing. It would do that just like seating bullets into the lands or creating a false shoulder with the lower part of the neck.

 

[nmbarta]

There is a simple way to see what's happening, though I don't have the exact science to explain it. It seems to be self explanatory to me. I've argued this point before, but I'm not always perfect when it comes to explaining how things look in my brain.
One measurement I haven't seen discussed here is the actual overall length of the case. If you fire your case once and the overall length of the case grows before sizing, this will indicate that you have stretched the case wall, which indicates that in your chamber with your brass, the shoulder is not being held in place via a false shoulder,jammed bullet or some other means. I'm sure other issues could cause this, but it does give you some indication of where the brass is moving. If a fired case does not grow in length (or grows very little), it's likely that the case is being blown out as it should be.
From what I've seen most brass will tolerate .020-.030 of combined growth, meaning that if you bump the shoulder .020 you should get 10-14 firing per case ( obviously dependent on quality) before your case has seen .020-.030 of stretch on the case wall.
This is part of the reason that I believe a lot of people have issues with belted mags, if not done right, you can see .012-.030 of stretch in the case wall in the first firing leaving very little for reloading.
If the wall blows out, you have a lot of life left, if the should blows forward, you have used up most of the life in the first firing....hence....case head separating in the 3 firings for some people.
Hopefully that makes sense.

 

[entoptics]

So rather than speculate, I did an experiment.

Quantitative analysis of brass volume, weight, and velocity.

See this thread for what motivated me to undertake this. https://www.longrangehunting.com/threads/0-03-growth-after-first-fire-264wm-ww-brass.254927/ Short story, had some extremely undersized virgin brass, and wanted to determine how this would affect processing and load development. There is...

www.longrangehunting.com

Summary?

Just shoot em!

I'll monitor incipient separation of course, but in terms of performance on target, there's absolutely no evidence that it makes any difference at all.

Also, for those questioning my headspace, as mentioned in a couple places in this thread, it was set with a Go-Gauge to minimum, with a piece of tape as a hard No-Go. The measurements on this rifle are essentially identical to my 7mm X-Caliber Savage pre-fit, which has perfectly normal "before/after" brass measurements.

In summary. It's undersized brass. Period.