Ideal case web sizing?

[1mechanic]

At Mikecr I agree .009" is too much what you are saying if I'm understanding this right at the case head your chamber should only be .0015" larger than the case?

 

[Mikecr]

The numbers I came up with; reamer print is .588, 3X fired brass is .586, sized brass is .584, new brass is .579.

Fired brass upsized from .579 to .586, that's 7thou upsizing already. He managed to downsize 2thou from there.
The problem is the 7thou upsizing.

 

[Mikecr]

At Mikecr I agree .009" is too much what you are saying if I'm understanding this right at the case head your chamber should only be .0015" larger than the case?

Yes
If you have that, and with normal/adequate breach support, your cases will spring back from chamber and extract freely -at SAAMI MAX). They will not yield to ever larger diameters in a runaway condition.
SAAMI Max is really the pressure point where FL sizing IS REQUIRED to reload.

 

[1mechanic]

Ok so at SAAMI max and full length sizing you're just over working the brass?

 

[nwmnbowhunter]

Your one time fired brass sizes fine? but your 3x fired neck sized only brass is hard to size correct?

In your situation you gotta full length size each time. Once the web expands that much you are not going to get it back down and keep it there.

You are basically blowing out the sidewall and you can't get it back in once it is blown out.

 

[nwmnbowhunter]

On my 300 prc i can also tell I'm going pretty high up in pressure by measuring the web on fired cases.

These cases don't show any ejector marks and no bolt lift or Clicker. But it is blowing the sidewall out and you basically have ruined brass.

Virgin = 0.529
Normal pressure = 0.531
High pressure = 0.5135

 

[Taylorbok]

Fired brass upsized from .579 to .586, that's 7thou upsizing already. He managed to downsize 2thou from there.
The problem is the 7thou upsizing.

so you think the factory brass is under size? I've honestly never compared un fired to fired at 200 line. What kind of brass are we dealing with?

 

[Mikecr]

Ok so at SAAMI max and full length sizing you're just over working the brass?

I wouldn't say that. I don't think there is anything wrong with SAAMI max.
I'm talking about excess clearances.

With any new setup (chamber/brass), I run a test for what I call [MyMax]. This is with brand new brass.
I'm also shooting across a chronograph to validate along with QuickLoad predictions that I'm not out of control or anything.
I incrementally load upward, 1 shot each, with cases that I've culled (probably thickness variance).
What I measure is the widest diameter of the case. The 'web-line'. I'll see it go up, level off, and then step change upward again.
This step change point is MyMax. And it is the point where body sizing will be required for reloading.
With all but one of my setups, as best as I can tell, MyMax has matched SAAMI max.
That's important to me because I do not and never will FL size brass.

With my latest cartridge, a 26wssm Imp, I went fitted chamber. That is no more clearance than 1thou from new case dimension (anywhere). For lower case body and neck I went 1/2thou total clearance. That's plenty really, and it raised MyMax to ~75Kpsi by Quickload. SAAMI max for the wssm line is 65Kpsi, and it happens that my chosen mid-node is right there.
I now have over 80 reloads on my wssm cases with no body or neck sizing at all. There are no issues, and since I don't size I don't trim or anneal. So the brass will last forever from this chamber.

You may chose a different sizing plan. Something less extreme.
But I can suggest that my thinking brings way less work, causing fewer problems.
It's already well adopted in many industries. Like for example, it's the reason why engines and oil last so much longer today.
But THIS industry, reloading, has not evolved.

 

[Rich Coyle]

The gunsmith in his town don't use his stuff. I personally had him redo a die three times.

So I was plying with a new die yesterday and had something happen I never experienced before.

When going to size a 3 times fired case I had a heck of a time getting the case up into the die. I quickly realized it was getting stuck above the web (about 1/4 way up from the case head). With this I started taking a bunch of measurements and looking at my reamer print. Then with determination I fully sized the case by going up and down several times sizing a little more of the case body every time.

The numbers I came up with; reamer print is .588, 3X fired brass is .586, sized brass is .584, new brass is .579. These numbers all sound fine to me but holy crap does the brass go hard. I've also never took a close look at how much is being sized near the web, .002 sounds good but that's also .004 smaller than chamber diameter. Is that getting on the sloppy side?

So my question is what is the ideal amount for a case to get sized just above the web? Should it be around .002, more, less?

Thanks for your time and help
Joshua

 

[MagnumManiac]

There is another problem with the .588" head size and dies.
Seeing all die manufacturers are still using a 1" die body for this, there is flex in the die! Trust me, I know this, I split 2 1" dies forming my 338-416 Rigby 45° shoulder. I then had 1 1/4" dies made and an adapter for my press. I do not struggle forming brass or sizing after fire forming…I did early on.

Cheers.

 

[Lonewolf74]

@Mikecr; you're saying the case should not need to be sized at all at the web and base as long as it chambers fine?

At case base just above extractor groove new brass and 3X fired brass all measure .586 the base or primer pockets are not growing at all. Above the web is where growth happens from .579 to .586. Keep in mind this is a wild cat with reduced body taper and 35* shoulder.

I have not sized a once fired case. I fired 5 cases 3 times with only partially neck sizing in between and sent them to Whidden to get a custom hydraulic form and full length bushing sizing die. Since receiving the dies I have hydro formed brass and bumped shoulders back to where I have a slight crush fit in chamber. I haven't got to shooting any of these yet but should be able to within this week.

Out of curiosity I went to size one of the 3X fired brass and that is when I found it was very hard to size just above the web. I tried to size all the fired brass and they all started to stick in the same spot. I fully sized one case with a great deal of effort so I could get some measurements.

 

[Lonewolf74]

Is there a good way to highly polish a die without hurting anything such as concentricity? It would appear with everything it wouldn't hurt if I enlarged the body portion of the die by .001-.002 but I'm not sure if there's a good way to do this?

 

[Mikecr]

@Mikecr; you're saying the case should not need to be sized at all at the web and base as long as it chambers fine?

Yes
But that doesn't mean you won't have problems. After all, you're upsizing lower bodies by 7thou in your forming.
Sounds to me like you're using the wrong baseline case, or a very poor wildcat design or just a poor reamer for it.
There is no good reason to accept or cause more than about 1thou of web area expansion.

The last few dies I had custom made (bump only dies) were done by JLC Precision (Jim Cartensen).
I don't know if they're still operating, nor how die makers open or close die dimensions.
But I'm sure there are folks who can open yours as desired. You got nothing to lose really.

 

[Lonewolf74]

Thanks for the reply Mike. I never took into consideration what the measurements were on the Peterson 338 Norma brass. I used standard chamber specs and did basically an Ackley improved with 35* shoulder. Once I received the brass I also found it was .011 short from base to shoulder datum so I had to create a false shoulder for my initial fire forming. If I do a wildcat in the future I believe I'll start with the brass and spec the reamer from that.