Headspace measuring and bump question.

[5RWannabe]

I have read on other posts to bump back the headspace off a fired casing .003''.

so i measured about 30 pieces of brass == 3x fired win brass. and got numbers ranging from 1.624 -1.627 with most being in the .025 to .026 range.

do i use a average being like .25 or .26 and take my -.003 from there? or do i bump back from the longest?


i am using a FL sizer die

 

[Fuzzball]

Re: Headspace measuring and bump question.

Taking an average of anything is never a good thing to do, it's always misleading. In this instance it simply insures about half of your resized cases will be too tight. Use the max lengths for your measuring and adjustments.

 

[MinorDamage]

Re: Headspace measuring and bump question.

Bolt or gas? I personally never bump my bolt brass back more than .002. I know that seems like splitting hairs. It is just my general rule.

Josh

 

[427Cobra]

Re: Headspace measuring and bump question.

Decap the brass then remeasure, primer flow can/does infulence the reading.

 

[Clark]

Re: Headspace measuring and bump question.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Fuzzball
Taking an average of anything is never a good thing to do, it's always misleading. ...</div></div>

And with a name like "Fuzzball" too.

 

[aquinas]

Re: Headspace measuring and bump question.

All good advice.

It's kind of hard to do anything if you don't know the chamber. You need some useful measurements. Those can be had with headspace gauges. Once you know that measurement, you can determine accurately how much your brass is growing and how much to set it back.

I know my exact headspace on my autoloaders. I set the shoulders back (gasp) .005. Never had any problems with brass life or anything else. I do this in a small base die.

If it's a commercial gun, most chambers are generous enough to accomodate minimal setback. Two other critical dimensions are neck diameter and body diameter. Headspace is not as critical as these two and as long as the chamber was not cut with a match reamer.

If the chamber was cut with a match reamer, next time send the smith a blank hornady headspace bushing and have him cut an exact duplicate of the chamber and use that to measure fired and sized brass.

 

[MinorDamage]

Re: Headspace measuring and bump question.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: himaster</div><div class="ubbcode-body">I set the shoulders back (gasp) .005. Never had any problems with brass life or anything else.</div></div>

I do .004 for my gas guns. Not sure if it reduces the brass life appreciably. 223 brass is cheap.

Josh

 

[BBeyer]

Re: Headspace measuring and bump question.

I have brass that has been shot 25 times and never had the shoulder bumped at all. This of course is brass shot in the same barrel.

 

[shoepop]

Re: Headspace measuring and bump question.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BBeyer</div><div class="ubbcode-body">I have brass that has been shot 25 times and never had the shoulder bumped at all. This of course is brass shot in the same barrel. </div></div>

If your FL resizing your bumping the shoulder back every time you size. If your bushing sizing or partial neck all I can say is -------------. Well I guess I'm at a loss for words.

 

[aquinas]

Re: Headspace measuring and bump question.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BBeyer</div><div class="ubbcode-body">I have brass that has been shot 25 times and never had the shoulder bumped at all. This of course is brass shot in the same barrel. </div></div>

Assuming it's a bolt gun. If it's an autoloader...don't shoot near me!

 

[thefitter]

Re: Headspace measuring and bump question.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: himaster</div><div class="ubbcode-body">

...next time send the smith a blank hornady headspace bushing and have him cut an exact duplicate of the chamber and use that to measure fired and sized brass. </div></div>

Could you please explain this in detail? I'm about to have a new barrel installed with a custom match reamer. Thanks

 

[vman]

Re: Headspace measuring and bump question.

Measure from the longest cases. It's best to go via trial and error by making small adjustments and trying to chamber the cases. When it goes from hard to chamber to easy via a small adjustment then you know your in the right place

 

[KevinU]

Re: Headspace measuring and bump question.

I'm using the O-ring under the die method to make .0005-.001 adjustments. Works great. As vman suggested, I take the longest case and bump/measure the shoulder until the bolt closes, a bump of .0015-.002 seems to work for me in my bolt rifle.

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

 

[5RWannabe]

Re: Headspace measuring and bump question.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fuzzball</div><div class="ubbcode-body">Taking an average of anything is never a good thing to do, it's always misleading. In this instance it simply insures about half of your resized cases will be too tight. Use the max lengths for your measuring and adjustments.</div></div>

good logic there fuzz<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MinorDamage</div><div class="ubbcode-body">Bolt or gas? I personally never bump my bolt brass back more than .002. I know that seems like splitting hairs. It is just my general rule.

Josh</div></div>

bolt remmy 700 5r

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: vman</div><div class="ubbcode-body">Measure from the longest cases. It's best to go via trial and error by making small adjustments and trying to chamber the cases. When it goes from hard to chamber to easy via a small adjustment then you know your in the right place</div></div>

the answer i was looking for<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: KevinU</div><div class="ubbcode-body">I'm using the O-ring under the die method to make .0005-.001 adjustments. Works great. As vman suggested, I take the longest case and bump/measure the shoulder until the bolt closes, a bump of .0015-.002 seems to work for me in my bolt rifle.

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

im gonna get me some of those o rings and give that method a shot. my headspaces come out where i set em, then get smaller and smaller, i believe its excess lube build up, im still learning how much lube not to use.


thank you all

 

[aquinas]

Re: Headspace measuring and bump question.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: thefitter</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: himaster</div><div class="ubbcode-body">

...next time send the smith a blank hornady headspace bushing and have him cut an exact duplicate of the chamber and use that to measure fired and sized brass. </div></div>

Could you please explain this in detail? I'm about to have a new barrel installed with a custom match reamer. Thanks </div></div>

You bet...either go to Hornady's website and order a blank headspace bushing. Have the smith cut that with the same reamer and to the same dimensions as your barrell. It will be an exact copy of your chamber. Attach to Hornady comparator body and you should get an actual headspace reading. Useful for sizing brass and seeing how much case growth you get after firing and before resizing.

You could also have him cut a piece of barrel chamber and basically do the same thing.

Here's the link:

http://www.hornady.com/store/Headspace-Gauge-Bushings/

It's "F" on the page.

Here's how I'd use it. You could just run with the bushing. Might work. But there's a better way. Sent this idea to Zen Master Glenn Zediker and Zediker agreed it was a good idea.

Here's how I use Hornady bushings: get a Forster match headspace gauge. A match gauge differs from go or no-go in that it gives the actual dimension on the gauge. Pop that in the hornady gauge. Now you have an actual number. Now zero the gauge and take a reading. I think I'm confusing you.

Let's take some numbers. When I resize .308, I take a match .308 Forster headspace gague and put it in the Hornady gauge, and zero the caliper. Digital calipers work best for this.I now know the zero measurement on the gauge is 1.630 (that's the forster gauge size).

Now I read the brass. A reading of -.001 means 1.629 actual case headspace measurement.

Why do I do this? Because one day I got the idea of putting my 1.630 match forster headspace gauge in my Hornady L-N-L headspace gauge. It should have read 1.630...right? It read 1.623! Off .007.

So I ordered 4 more gauge bodies from hornady. They read all over the place: 1.614; 1.617; 1.623 and 1.627.

So now I zero off the Forster gauge which gives me a definate starting place.

The advantage of having a bushing cut with the reamer is that they will headspace at exactly the same point. The datum lines can be off just a hair. Doing it this way, they are dead on.

 

[thefitter]

Re: Headspace measuring and bump question.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: himaster</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: thefitter</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: himaster</div><div class="ubbcode-body">

...next time send the smith a blank hornady headspace bushing and have him cut an exact duplicate of the chamber and use that to measure fired and sized brass. </div></div>

Could you please explain this in detail? I'm about to have a new barrel installed with a custom match reamer. Thanks </div></div>

You bet...either go to Hornady's website and order a blank headspace bushing. Have the smith cut that with the same reamer and to the same dimensions as your barrell. It will be an exact copy of your chamber. Attach to Hornady comparator body and you should get an actual headspace reading. Useful for sizing brass and seeing how much case growth you get after firing and before resizing.

You could also have him cut a piece of barrel chamber and basically do the same thing.

Here's the link:

http://www.hornady.com/store/Headspace-Gauge-Bushings/

It's "F" on the page.

Here's how I'd use it. You could just run with the bushing. Might work. But there's a better way. Sent this idea to Zen Master Glenn Zediker and Zediker agreed it was a good idea.

Here's how I use Hornady bushings: get a Forster match headspace gauge. A match gauge differs from go or no-go in that it gives the actual dimension on the gauge. Pop that in the hornady gauge. Now you have an actual number. Now zero the gauge and take a reading. I think I'm confusing you.

Let's take some numbers. When I resize .308, I take a match .308 Forster headspace gague and put it in the Hornady gauge, and zero the caliper. Digital calipers work best for this.I now know the zero measurement on the gauge is 1.630 (that's the forster gauge size).

Now I read the brass. A reading of -.001 means 1.629 actual case headspace measurement.

Why do I do this? Because one day I got the idea of putting my 1.630 match forster headspace gauge in my Hornady L-N-L headspace gauge. It should have read 1.630...right? It read 1.623! Off .007.

So I ordered 4 more gauge bodies from hornady. They read all over the place: 1.614; 1.617; 1.623 and 1.627.

So now I zero off the Forster gauge which gives me a definate starting place.

The advantage of having a bushing cut with the reamer is that they will headspace at exactly the same point. The datum lines can be off just a hair. Doing it this way, they are dead on. </div></div>

Thanks. I was told that many gunsmiths do this for the customer they re barrel a rifle. It's sometimes called a "gizzy"??