Getting brass to headspace to rifle chamber?

[sithlord6512]

I want to adjust my RCBS FL sizer die to the correct headspace (have RCBS's precision MIC). I was informed that my brass should be fired at LEAST TWICE before trying to set my die to the headspace of my chamber (RCBS Tech).

I am missing something. Why would firing at least TWICE make a difference - wouldn't I just be resizing rezise my brass back to headspace dimension of the my die each time (i.e., no closer to the headspace of my gun).

Based on some I the things I have read on this forum, the only theory I can think of is that brass will tend to "springback" less with each firing. Therefore, as I fire the same brass in the same rifle a number of times, the less it will springback, and therefore, the more closer a match it will be to the chamber of my gun. Is this theory correct?

If my theory is correct than I figure I can just FL resize as normal. If incorrect, then do I need to consider a different type of resizing (e.g., Partial FL resizing or neck sizing) at first, in order to get brass to the same size as the chamber of my gun?

 

[rick smith]

Partial Full length sizing will work the brass less than FL sizing on every reloading. A FL sizing die is made to return brass to it's original size which could be more sizing that is necessary for your chamber. I neck size until the brass gets tight to bolt closure then PFL bumping the shoulder back 1-2 thousants. This becomes more important with some liberal chambers and/or belted mag cases which should be sized to headspace on the shoulder and not the belt.Rick.

 

[Savage99]

sithlord,

You should be able to FL size once fired brass to fit your chamber to the shoulder if the cartridge has an adequate one.

Just FL size a fired case part way and try it in your rifles chamber. Size it some more until it fits. That the bolt closes ok but you can just feel it.

 

[old #7]

Partial Full length sizing will work the brass less than FL sizing on every reloading. A FL sizing die is made to return brass to it's original size which could be more sizing that is necessary for your chamber. I neck size until the brass gets tight to bolt closure then PFL bumping the shoulder back 1-2 thousants. This becomes more important with some liberal chambers and/or belted mag cases which should be sized to headspace on the shoulder and not the belt.Rick.

Bingo.

 

[JD338]

Partial Full length sizing will work the brass less than FL sizing on every reloading. A FL sizing die is made to return brass to it's original size which could be more sizing that is necessary for your chamber. I neck size until the brass gets tight to bolt closure then PFL bumping the shoulder back 1-2 thousants. This becomes more important with some liberal chambers and/or belted mag cases which should be sized to headspace on the shoulder and not the belt.Rick.

That is exactly how I resize my brass also.

JD338

 

[FOTIS]

Unless you're using a neck sizer or Lee collet dies you will resize some of the shoulder. I have never been able to not touch the shoulder at all with full length resize dies.

 

[RiverRider]

You must bump the shoulder back---even if it's just a smidgen---each time you resize. I say you must bump the shoulder because if the case body is getting squeezed down to any degree at all, the shoulder has to move forward at least a little bit as the case moves up into the die. So, as the case moves up into the die the shoulder is moving forward a little and that last few hundredths or thousandths of an inch are pushing the shoulder back to where it belongs. It ain't a perfect method (but I think it's a good compromise). This is the concept I employ when setting up my resizing dies for partial full-length sizing.

I've never used an X-die and don't remember a darned thing about how they work. I guess I'll just have to go look it up while I'm thinking of it...I hope I don't find it incredibly and irresistibly impressive---I can't afford to buy a half-dozen of the darned things!

 

[Ridge_Runner]

here is what I do

say I'm setting up a 7mm/08, I use either a 308 case or a 7mm/08 case that has had a .308 expander ball ran through it.

I leave the FL sizer up a good bit, lube the case and resize it, by inspecting it each time you size you can see when your getting close, start trying it in the rifle after each trip through the die, and screwing the die down a bit after each sizing.

when you can just feel a bit of resistance when the bolt goes down, screw the die down 1/8th to 1/4th turn and lock it down, your running minimal headspace.
RR

 

[Ol` Joe]

Unless you're using a neck sizer or Lee collet dies you will resize some of the shoulder. I have never been able to not touch the shoulder at all with full length resize dies.

Get a set of Redding competition shell holders. They come in 0.002" increments and will allow the shell hold to contact the ram and keep the die from contacting the shoulder more then is needed.
http://www.midwayusa.com/eproductpage.e ... mid=525874

 

[Innovative]

The RCBS Precision Mic is a neat handloading tool, but the it's designed for use on one specific caliber only, and it's very slow. The Redding competition shellholder set is also a good tool, but it only works for calibers that use the same shellholder.

Check out our Digital Headspace Gauge and see what you think. It gives you a quick reading on the exact chamber clearance in your particular chamber, and it works on all calibers. Check it out ...

- Innovative

 

[RiverRider]

It's easy enough to adjust the seating die by resizing a little more at a time until the effort required to close the breech on the case just begins to decrease. What advantage is there to using this gadget?

 

[Innovative]

I'm glad you asked. The advantages are that you can compare your handloads to a fireformed case, and get a measurement showing your "exact" chamber clearance. You can also quickly compare all of your resized cases. This often shows that the headspace isn't always exactly the same. Out of 50 cases, I'll usually find a few that differ as much as .002"

This "gadget" also compares loaded handloads for uniform bullet seating (from the ogive) and it doesn't require special bushings or balancing cases on the blade of calipers. This exposes irregular bullet shapes and irratic seating depth.

If you ever need to measure Case length on a bunch of cases, this will do one case per second.

- Innovative

 

[rick smith]

How movable is the platform, besides being removed of course, that is positioned on the shoulder.Rick.

 

[Innovative]

Rick,

I'm not sure if I understand your question. The adjustable V-Block (on the stem of the gauge) is firmly connected. Except for the adjustable inside diameter, it has absolutely no movement at all. The platform (base) is machined from a block of 6061 T6 aluminum. You can read all about it on our website.
- Innovative

 

[rick smith]

If the adjustable V-block has no movement, how do you position longer cases into the device?Rick.

 

[Innovative]

Rick,
OK . . . . now I see what you mean. The gauge moves up and down on the vertical shaft. That way it can measure anything from 22 Hornet cases to the 378 Weatherby. (A picture is worth a thousand words) Our website also shows the instructions for using this new tool.

This is our new Digital Headspace Gauge. It has other uses for shooters that reload. It can measure overall cartridge length "back from the bullet ogive". That shows when you have inconsistent bullet seating depth and it also exposes inconsistent bullet shapes. Pretty cool aye?

- Innovative

 

[rick smith]

Thanks for the info. Guess if the picture was turned a little I would have seen the adjustable dial set-up. Checked the website but didn't click on more info, come on, guys don't need directions!!!!Rick.

 

[RiverRider]

If I can't adjust my sizing die so that cases fit the chamber perfectly (and I can tell by the feel!), then all the measuring in the world isn't going to help me. Looks like a total waste of money to me. I guess I got vaccinated against gadgetitis somewhere along the way.

 

[Innovative]

RiverRider,

Read the instructions and you'll find that this tool does more than you might think. It's not for everybody, but it can help shooters discover bullet seating problems and irregular bullets that can ruin your accuracy.

- Innovative

 

[RiverRider]

"Lower the indicator until the V-block is positioned anywhere on the case shoulder, then lock the indicator in position."

This is the achillles heel. If chambers (and dies) were cut with perfect conformity and uniformity, it might work in a meaningful way.

The same holds true for determining just *exactly* where the ogive begins on a bullet's profile and determining a corresponding dimension in a rifle's chamber for the purposes of seating bullets a certain distance from the lands. If a comparator could be built that exactly mimics the chamber of my rifle, I could know precisely how far I am seating from the lands. But it doesn't happen that way...and even if it did, I would need a seating stem in my seater die that bears on the bullet's profile where the ogive begins if I was to have any hope of seating a bullet "perfectly." None of this is practical.

In the real world, I have to accept the variability in bullet dimensions and the limitations imposed by practical seating stem design. I also have to accept the imperfection of the way my chamber is cut as well as the way my resizing die is manufactured.

Measuring is cool, but it doesn't fix a damned thing.