Headspace & Accuracy

[Curious]

Im currently running 0.002" headspace on my BRA brass, Ive done the same with BRs and Dashers in the past. One of the things Ive never got around to testing (of which there are many) is the effect headspace has on accuracy.

My questions today are;

How much do you bump your shoulders from the fired position and what headspace does that give you?

Have you established a headspace that gives you optimum accuracy, if so what is it?

Have you ever tested to see how much headspace has to change before accuracy starts to suffer?

Im particularly interested in the BR variant type cases but would be very interested to here from our short range brothers as well. As always many thanks to those who contribute to this thread

 

[mikeeg02]

I dont have paper results, but I had a bad weekend last weekend lol.

I generally bump the it back until the bolt just closes smoothly across a couple cases. Which puts me between .002" - .0025". I have a real good light gun barrel, and last weekend I messed up my settings and went to ~.0045". I didnt have time to test it or correct it before hand, and shot it at a steel match sunday. The results were not good, but neither where the conditions. But from what I saw, the barrel wasnt doing what it did before. This was all in a BR-A. I did the same in my dasher and BR, and I dont see why you would want to do it any other way, but I have been fooled before!

 

[KenOath]

With my straight BRs i pushed shoulders back .0005” to .001” which gave me no issues at all... I did the same thing with my first Dasher and initially was having troubles finding a consistent load, so started changing things to fix it. One of the things I changed after reading something Wheeler put up somewhere was to push Dasher shoulders back at least .002”, so pushed em back .002” to .0025” and i definitely seen an improvement in consistency, not 100% sure why, maybe it has something to do with 40deg shoulders needing more clearance..

 

[pat fulghum]

I generally bump the it back until the bolt just closes smoothly across a couple cases.!

+1

Which is just at .002

 

[ShootDots]

With cartridges that I run up at or slightly above the 62-63,000 P.S.I. range, I bump them back 3 thousandths. I believe that the 3 thousandths bump "absorbs" some of the initial pressure and "evens out" any potential pressure spikes. With lower pressure cartridges, 1-2 thousandths is fine in my humble opinion. The "neck sizing only" crowd, if they run cartridges that generally run over 60 thousand P.S.I., will get pressure spikes and inconsistent accuracy, if not out-right pressure problems.. Most of my competition cartridges will get the 3 thousandths shoulder bump and I do believe it contributes to consistent accuracy..

 

[dmoran]

No less then .002" and no more then .003" is what I get best results from in my 1000-BR rifles.

 

[sdean]

Depending on neck tension, what makes you think you have any headspace after the firing pin pushes the case up?
I know years ago I read on BRC a guy did some testing with dead primers measuring how much the firing pin pushes the cases up on jammed bullets. It was more than you would think. I am not sure the results would be quite the same if the case actually fired.
I kinda think that is why jumped bullets can be so accurate. When the firing pin shoves the case up the shoulder centers the cartridge. But then what the hell do I know.

 

[Curious]

Depending on neck tension, what makes you think you have any headspace after the firing pin pushes the case up?

That confuses me.

Headspace is something we measure before the firing pin hits the primer. If entering the case on the shoulder was vital again we could control out brass to do that at the resizing stage.

 

[Curious]

No less then .002" and no more then .003" is what I get best results from in my 1000-BR rifles.

Will all of your brass come out of the die within that tolerance?

 

[msinc]

Will all of your brass come out of the die within that tolerance?

This is a good question. Mine wont. To clarify, most of them will size to exactly what I set the die to, but some, for various reasons and some reasons I haven't really figured out yet, will not. The numbers usually look like this; out of 200 cases there will be about 10-15 that size a thou or two under and 10-15 that don't quite hit the mark but usually do if I run them again. It will be more cases that come out right if they were recently annealed {obviously...} and if they need to be annealed, depending on how bad they are I might get many more that size to a different length because of spring back.
When it's "resize day" at my reloading bench I try to wait until I have a significant amount of brass to size, set up the die and run them all. Then I recheck every case for headspace length and separate the ones that are not "on size". Once I get the resize die set to where it is working good and hitting the mark for the most part I want to run every case I have that needs it if I can. For me it seems to be a numbers game...the more cases I have to resize the more I will end up with that are dead on.
As to the original question, I find that different rifles I have like it set different, but not much. None are more that .002" with that being average. I have played around with it a lot with my guns and cannot nail down any definitive amount. Two of my rifles seem to shoot best at dead zero.

 

[Ledd Slinger]

I think the variation you're seeing is certain pieces of brass not taking the annealing process evenly or completely. I measure headspace on each case after sizing, always freshly annealed befor sizing. I will find a few cases out of spec after sizing from time to time just like you are saying. At the end, I take the out of spec cases and run them through the annealing machine for a 2nd round, size them again and re-measure. If any are still out of spec, they get marked and used for foulers/sighters. Often times the 2nd round of annealing and sizing brings them into spec.

 

[Steve Ladino]

Im currently running 0.002" headspace on my BRA brass, Ive done the same with BRs and Dashers in the past. One of the things Ive never got around to testing (of which there are many) is the effect headspace has on accuracy.

My questions today are;

How much do you bump your shoulders from the fired position and what headspace does that give you?

Have you established a headspace that gives you optimum accuracy, if so what is it?

Have you ever tested to see how much headspace has to change before accuracy starts to suffer?

Im particularly interested in the BR variant type cases but would be very interested to here from our short range brothers as well. As always many thanks to those who contribute to this thread

When I first started with BR rifle shooting the common opinion was to go with the 6 BR and I did. I ordered a D Kiff reamer and a Krieger from Bruno's. Chambered it and bought 100 Lapua cases. Used a Wilson NK. sizer die ( before threaded in type). Shot and reshot those cases without bumping or annealing them at least 20 times. Whatever the springback was it was enough and that rifle shot very well. It wasn't until I bought another complete rifle and newer Lapua brass that I had to bump and work more on my brass to get them to chamber smoothly.

 

[urbanrifleman]

This is a good question. Mine wont. To clarify, most of them will size to exactly what I set the die to, but some, for various reasons and some reasons I haven't really figured out yet, will not.

Here is the big elephant in the room.

I just bought 300 rounds of Lapua 6BR ammunition. In my 6br that has a very minimum headspace. Each case feels different. Some are tight and some are loose, some are just right. If the chamber is really close you can feel it. The idea that there is a zero tolerance on case headspace is ridiculous, not even the factory can do it. If found that the 600 rounds of 223 Lapua ammo I bought had the same tendencies. Some were too short to fireform in an Ackley.

It's brass. It's hollow. It is going to vary.

 

[moondog]

usually size all my stuff .002-.003. When I got the BRA, I did the same. fought it for
couple hundred rounds before I realized it wanted .0045. Right, wrong, or indifferent
It shoots lights out now

 

[ShootDots]

usually size all my stuff .002-.003. When I got the BRA, I did the same. fought it for
couple hundred rounds before I realized it wanted .0045. Right, wrong, or indifferent
It shoots lights out now

You must be running at or above 65,000P.S.I., am I correct?

 

[#40Fan]

How are you guys able to bump 40° shoulders? I have a couple .243 AI and if I try to move the shoulder, it just buckles the cases just below it. I have just been running them through the FL die with just the tiniest amount of contact with the shoulder which gives me smooth chambering. Annealed after every firing.

 

[Ledd Slinger]

Here is the big elephant in the room.

I just bought 300 rounds of Lapua 6BR ammunition. In my 6br that has a very minimum headspace. Each case feels different. Some are tight and some are loose, some are just right. If the chamber is really close you can feel it. The idea that there is a zero tolerance on case headspace is ridiculous, not even the factory can do it. If found that the 600 rounds of 223 Lapua ammo I bought had the same tendencies. Some were too short to fireform in an Ackley.

It's brass. It's hollow. It is going to vary.

So you are chambering brass straight out of the box? Of course they're gonna feel different. I don't care how much money you spend on brass, something produced in a factory will never be as consistent as what can be made at a bench by a handloader. If factories could produce ammunition better than us, the art of handloading wouldn't even exist. In my opinion, there's no such thing as brass that's "ready to load" straight out of the box.

 

[urbanrifleman]

So you are chambering brass straight out of the box? Of course they're gonna feel different. I don't care how much money you spend on brass, something produced in a factory will never be as consistent as what can be made at a bench by a handloader. If factories could produce ammunition better than us, the art of handloading wouldn't even exist. In my opinion, there's no such thing as brass that's "ready to load" straight out of the box.

Lapua Ammunition. And it is really beside the point. The headspace is going to vary slightly.

 

[Curious]

Lapua Ammunition. And it is really beside the point. The headspace is going to vary slightly.

New unfired cases will vary, fired ones wont and then its up to us to resize them consistently to the required head spacing.

 

[Cuando]

usually size all my stuff .002-.003. When I got the BRA, I did the same. fought it for
couple hundred rounds before I realized it wanted .0045. Right, wrong, or indifferent
It shoots lights out now

So, it wasn't shooting until you bumped shoulders a bunch? How much of a change did you see?

This subject of bumping shoulders and seeing results on paper is very interesting.