Headspace Mysteries!

[Lawdwaz]

I found a link on another site that I thought might be of interest here.  Getting headspace right has always been kind of a chore for me but so far, so good-I still have all my fingers, toes AND eyes!

 

This link is a great read on the subject, especially the link found in the link (in blue) called "headspace".  The main link is referring to case size dimension changes and the second link (headspace) refers to the proper way to set up dies. 

 

The main link:

 

http://riflemansjournal.blogspot.com/2010/06/basics-resizing-case-dimension-changes.html

 

The headspace link:

 

http://riflemansjournal.blogspot.com/2009/08/reloading-headspace.html

 

 

 

 

[RSRAINS]

As a benchrest shooter after we fire form a Lapua 220 Russian case and turn it into a 6ppc.

 

What we will do is fire the case in the chamber of choose take a measurement from the base to a shoulder junction on the case (reseat primer so you do not get a false measurement).

 

They have tools that will sit on the shoulder to take these measurements but you can use something as simple as a 1/4 drive socket that will fit over the neck and rest on the shoulder of the case. Fire that case, reseat the primer, measure then write this measurement down.

 

Size the case with trying to bump the should back 1-3 thousands from the measurement you wrote down. Then fire the case reseat the primer and measure it again this should be the same number you wrote down the first time using the same tools.

 

That will be your head space using the same tools for that chamber.

 

Learn to bump the should back 1-3 thousands then you can remove the firing pin from your bolt action rifle install the sized case into the chamber and you should feel very slight resistance at the bottom end of closing the bolt. You should not have to apply mush pressure on the bolt for it to close fully.

[Lawdwaz]

Thanks for your version.

 

 

[Pygmy]

I've been reloading for 40 years and it's STILL a mystery to me, and I still have 3 fingers remaining on my right hand counting my THUMB, of course..

Edited January 6, 2015 by Pygmy

[bkln]

In my limited reloading experience (NOT 40 years :-)) I would say load and test, load and test and the load and test some more... each rifle is different, that's the beauty of reloading you can find that sweet spot you need for YOUR rifle....

[RSRAINS]

We call that tuning our rifles weather it be Powder, Bullets etc.

[Lawdwaz]

I don't think setting headspace has anything to do with tuning a rifle. It's not like you try different setting with a you sizer die then shoot for groups, do you?

No.....

[pistolp71]

Rsrains has it right. Some get intimidated by the whole headspace thing but its really not that hard. 

 

All you need is the hornady headspace gauge kit and a good micrometer. Bolt guns you want very minimal should push, about a thousandth. Semi autos should have about 3-5 thousandths just for reliability. And yes, tuning is primers,powder,bullets,oal, not headspace.

[Lawdwaz]

I posted the links in the OP as an "FYI thing" as headspace can be a difficult thing to grasp sometimes with all the changes to the case when firing then the different types of sizing.  FL, partial FL and neck sizing are all very different and can have different consequences.  The links talk about those changes and give measurements and suggestions.  

 

I have the Hornady headspace tools (and bullet comparator)  and a good micrometer and have a pretty good handle on things after 24 years but am still learning!

 

Lapua brass is one of best moves in the 223, 243, 7-08 (308 necked down) and now the 260 that I have made............necessary?  Probably not but it sure is nice to work with. 

[pistolp71]

And for those that don't know. In short, headspace, is the distance from the case head(bottom part where the primer is) to that datum line(the part of the shoulder that stops the case from moving forward). Excessive headspace could cause case head separation. You don't want to push the should back excessively when resizing.

 

Lawdwaz, I primarily use Lapua brass myself, great stuff. Along with annealing, it last forever. Not sure what Lapua brass has to do with headspace though...

[Lawdwaz]

Lawdwaz, I primarily use Lapua brass myself, great stuff. Along with annealing, it last forever. Not sure what Lapua brass has to do with headspace though...

 

It probably has little to do with headspace but for me it helps take any doubt about the quality of the brass I'm using.

 

Sometimes I question WTH is going on with things but with the Lapua brass I know the consistency is there and I don't have to worry about too much.

[wildcat junkie]

I use powdered mica on the case necks for lube. It shows exactly where the die stops. I want the die to just kiss the shoulder when loading for a specific bolt action rifle.

 

The cases fired in my 7mm-08 M700 Mnt Rfl DBM as well as loaded cases resized for the same chamber needed the dies set considerably shorter for the Savage AXIS-II I recently worked with. 

 

Ammo loaded for the M700 would chamber only with considearble bolt closing resistance in the Savage. After re-setting the dies there was just slight resistance at the very last bit of bolt closure, just enough to feel positive headspacing. It took some trial & error to achieve that precise fit.

 

Cartridges loaded for semi-auto, pump or lever actions should usually have the dies screwwed down all the way for full length resizing.

 

Also be aware that insuffecient case lube will cause the rim to pull slightly as the die is withdrawn giving a false (tight) headspace "feel". If you suspect such a situation, color the case head W/some sort of dark marker & pass it lightly over some fine emory or sandpaper laid on a hard flat surface (or a fine mill file) to see if there is a high spot. If you find that situation, set those cases aside & re-visit your case lube procedure & die setting.

 

DO NOT attempt to flatten the rims W/stock removal! If the rims aren't severely deformed, you could probably salvage those "tight" feeling cases by loading them with moderate pressure plinking loads which will flatten the rims back to spec'.

Edited January 6, 2015 by wildcat junkie

[pistolp71]

Yup, usually several ways to achieve the same result.

 

Wildcat junkie, I'm a bit of a wildcat junkie myself. Love my 6-284, 6 dasher, .257 Roberts ackley, 6-06 Ackley. And gonna build a .20 Vartarg next.

[wildcat junkie]

Yup, usually several ways to achieve the same result.

 

Wildcat junkie, I'm a bit of a wildcat junkie myself. Love my 6-284, 6 dasher, .257 Roberts ackley, 6-06 Ackley. And gonna build a .20 Vartarg next.

I started my reloading adventeures W/an 8mm-06 Ackley Improved.

 

W/180gr .323 NBTs @ 3000fps, it would blow chunks of Whitetail lungs the size of walnuts onto the ground. Unfortunately the guy that did the barrel turned it too thin & it walked POI.

 

I'm going to get another barrel chambered for it W/a beefier profile. W/the new modern high energy powders I should be able to get about 2900fps W/200gr pills.

[wildcat junkie]

 

 

Lawdwaz, I primarily use Lapua brass myself, great stuff. Along with annealing, it last forever. Not sure what Lapua brass has to do with headspace though...

Does Lapua brass have drilled primer flash holes like Norma or are they punched like U S brass? Are the case heads a full .473"?

 

I like '06 Norma brass for my 8mm-06 A.I. because of the drilled flash hole & case spec's that wern't undesize like U S cases. Lapua is considerably less expensive than Norma.

[RSRAINS]

I don't think setting headspace has anything to do with tuning a rifle. It's not like you try different setting with a you sizer die then shoot for groups, do you?

No.....

If you have the incorrect headspace this will affect your groups and in the end effect the tuning of your rifle.

 

Now lets bring up concentricity of a sizing die and or a loaded round for a setting die and then measuring run out.

 

But that's another chapter.

[pistolp71]

Case heads measure .471. And the flash holes are drilled and perfectly centered.

[pistolp71]

Speaking of concenticity, I just broke down for a Sinclair gauge last week. I'm right around a thousandth runout.

[RSRAINS]

A thousandths run out for a hunting rifle is very good.

 

Put a rubber band on a pencil and roll your case on you Sinclair Concentricity tool using the rubber band against the case and roll the case you will get better readings. 

 

[Lawdwaz]

If you have the incorrect headspace this will affect your groups and in the end effect the tuning of your rifle.

 

Now lets bring up concentricity of a sizing die and or a loaded round for a setting die and then measuring run out.

 

But that's another chapter.

 

Damn....what I mean is that once the HS is set, you don't monkey with it as far as "tuning" or accuracy.  Its set, its set....... 

[RSRAINS]

Head Space can change depending on how many times the brass has been fired you may have to adjust your die to adjust the head space on the work hardened brass.

[Lawdwaz]

Head Space can change depending on how many times the brass has been fired you may have to adjust your die to adjust the head space on the work hardened brass.

 

 

You have an answer to everything..........

 

I'm not talking about any changes after multiple loadings I'm talking about changes someone might make during load work up.  That is all.

[RSRAINS]

You have an answer to everything..........

 

I'm not talking about any changes after multiple loadings I'm talking about changes someone might make during load work up.  That is all.

I was only trying to help but if you don't need any I can understand.

 

Enjoy your reloading and may it be done safely.

[Lawdwaz]

I was only trying to help but if you don't need any I can understand.

 

Enjoy your reloading and may it be done safely.

 

Maybe you should read post #1 in this thread because I don't think you did.

[wildcat junkie]

I haven't seen case length addresed & it is a very important factor. With each firing & resizing, the case will grow slightly in length.

 

If case length gets long enough, the case mouth will effectively "headspace" at the end of the chamber.

 

If this gets to extremes, the case mouth can become crimped in a tight chamber spec elevating chamber pressures as it impedes the release of the bullet from the case.