Minimum headspace question

[mjphawk]

Is there a downside to having your headspace set at minimum?

I just did my first barrel swap on my savage 308Win. I use the gun for shooting groups and long distance.

I think I have the headspace set almost EXACTLY at minimum. The real question is do I WANT absolute minimum.

Go gauge, FGMM, and new Lapua brass closes just fine. My used Lapua that I full length sized closes tight (+0.0025"). I may need to try resizing again with a strong cam-over to get the used brass down to size or will need to switch to a separate body and shoulder bump die. I would expect the dies should bump my shoulder back to minimum

I have never heard of anyone wanting to increase the tolerance on their headspace bit thought I would ask those more experienced.

1.6200 - 1.6210: go gauge
1.6195: FGMM
1.6200 - 1.6210: Lapua new
1.6225: Lapua used and resized




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[Robinhood]

If you reload you can do what you want. You may have to remove .001 or 2 from the bottom of the die to get the clearance you need though. As for increasing the headspace, Since you reload you can raise the die and maintain the small shoulder clearance you want. Since you reload size the brass to fit your chamber.

Try not to overwork you brass.
If you neck size, after the first firing you will not have to push the shoulder back until you feel resistance closing the bolt.
If you full length size, Do not use a die that squeezes your neck down .012 then opens it back up .008 to get the right neck tension. find a product that gently reduces the neck and a button that brings you right back to the right tension.

If you notice that new brass sizes correctly but used brass does not, think about selling the brass and buying new or try annealing. Be careful with a do it yourself method or you will flash the zink out.

[RC20]

The experts like to have their brass snug, just a shade of bolt resistance closing.

FGMM Federal Match of some kind?

One guy I know who is a gunsmith/target shooter likes it firm. I don't but he has been at it a lot of years. Yours sounds like its in his preference.

First up I am an admitted Full Length re-sizer, so my methods are all based on that.

Others like the neck and small base dies. FLA suits me and I have had no issues when done right.
Longer term I do have access to an induction annealer (I do mine once every 5 rounds)

I don't claim to be a pro shooter, but FLA is what they use as well.

If you are just measure case COAL it does not work that way. The close issue take place at the shoulder. If you measure to the shoulder with a comparator set (aka Hornady and a micrometer) then you can tune that setback with the die.

Robinhood is right that you can get by without a setback for a few rounds. Then you have to do it anyway. I follow the anyway school of thought and set it back as little as possible (ideally .002)

Your shot case will grow COAL a bit when you shoot it and at some point need trimming, but that is not the same as a re-size nor is it what makes the case tight.

You also trim (if needed) after the resize.

1. to give yourself the brass brass life, you can turn the dies down more, but that is pretty tricky unless you have a shoulder OGIVE tool. It does not take much. We are talking like 1/32 of a turns here. You can do a tiny adjustment, check the case in your gun and repeat.

Or get the tool and go for .002 setback.

That is preferred as your die setup changes each time unless you have a dedicated press and impossible to set back exactly where it was once you take the die out, you have to re-do it (same with the tool but easier in my view)

The minimal bump back fits both your chamber and keeps from stressing the brass down the base which if done the hard cam over will break at 8-10 firings.

I do mine in lots of the same mfg, check every 5 or 10, recheck if I change mfg brass.

2. You could leave your adjustment as is and turn the barrel out a shade, check, nut back tight, recheck. Repeat if need be.

The problem there is it only works the one time for that dies setup and it probably won't be right for the next one.


Brass: I have had poor results with Federal Brass. Its very soft, if I am going to tear a case head off it will be with Federal.

Also have not been able to make it last. I am of mixed mind on it, even free of that its less an issue to go with once fired (I like RP) or Lapua (most reasonably priced and they com in lots of 100 and compared to theirs its more up front but you get twice as much and is less expensive per case). I haven't been shooting it long enough to see how it does long term, reports are uniformly good.

I use RP to test and then when I have something that looks promising I shift to the Lapua.

I have some PPU as well, mixed feeling on it, seems a bit harder than I like. Ok, about the same overall as RP in my opinion.

If you weigh the cases you will usually find FC is the heaviest, RP under it and then the rest trails off.

I forget where Lapua comes in, PPU is right at the same weight.

I started thinking FC with the weight would hold up the best but as its soft I have not found that to be true.

[mjphawk]

I ran a few pieces back through my FL sizer with a strong cam at the end to make sure it seats fully into the die. Still coming out 0.002 longer than my go-gauge (base to datum line). Bolt close is a tiny bit stiff but not too bad. Do I:

1) keep headspace as is. Shoot used brass with stiff bolt close to fire form. Call die manufacturer to inquire why I'm not getting down to min SAMI spec.

2) add 0.001-0.002 to headspace and manage headspace with die adjustments.

I'm leaning toward leaving as is since the factory ammo and brass loads no problem but then I have to either fix the problem with my FL sizer (not comfortable shaving it down) or having to full length AND shoulder bump if I need to get a full length resize.

After initial fire forming I generally neck size only with a Lee collet die. Seems to be an issue with my FL die or I am getting too much spring back on the brass due to work hardening (4-5 firings, no annealing)?


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[shagerott]

I have found some variation in case holders. I took one RCBS and sanded the top smooth and was able to go a few thousandths shorter. I wanted to save the die.

[Robinhood]

Shagerott has a good point.

Also, if you are sizing your own brass why not adjust head space to where the nogo does not close but the go has clearance. Your #2 solution plus. There is like .007 tolerance on a 308.

[mjphawk]

Thanks Shagerott. I meant to mention I tried who different case holders with exact same result.

Robinhood, I may end up going this route depending on what Forster tells me when I call them tomorrow. Interesting you like 0.007 clearance. I would have thought that was a lot. I thought the difference between go/no-go was about 0.045.


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[gbflyer]

I find absolute SAAMI minimum headspace to be a source of frustration, namely the afore mentioned dialing in of the FL die. I prefer a little slack so I put a piece of scotch invisible tape on the base of my go gauge and cut it into a nice little circle with a razor blade. I like it to just start to drag just before the bolt closes. Seems to give me the clearance I like and no way the no go will even think about closing. I don't have the best feel for it, too many years with hands in the cold water, so I have to strip the bolt to get there. I understand others are successful without tearing it down.

It's been my experience that this causes no ill accuracy effects. Seems like a barrel is going to shoot or it isn't.

Good luck. Let us know how you come out!

[mjphawk]

I find absolute SAAMI minimum headspace to be a source of frustration, namely the afore mentioned dialing in of the FL die. I prefer a little slack so I put a piece of scotch invisible tape on the base of my go gauge and cut it into a nice little circle with a razor blade. I like it to just start to drag just before the bolt closes. Seems to give me the clearance I like and no way the no go will even think about closing. I don't have the best feel for it, too many years with hands in the cold water, so I have to strip the bolt to get there. I understand others are successful without tearing it down.

It's been my experience that this causes no ill accuracy effects. Seems like a barrel is going to shoot or it isn't.

Good luck. Let us know how you come out!

Thanks. I didn't think about the tape to do this despite that being what I did for my no-go gauge (go gauge plus 2 pieces tape).


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[Nor Cal Mikie]

IMHO, if you have "slight" resistance when closing the bolt, I would open up the headspace "just a little". As the brass gets work hardened, it won't go down in specs like it did when you first started. It would help to leave yourself a little "wiggle room". No modifying dies to get what you want. Fresh "soft" brass, full length resized that fits the chamber with no to very slight resistance. It'll be a feel thing.
And when you resize, make it a point NOT to work your brass any more than needed. It's a toss up between full length and shoulder bumping your brass. Most of the BR shooters that full length resize are using custom cut dies that match their chambers. Brass barely moves. I shoulder bump and neck size then body size when/as needed. If your untouched fired brass will fit back in the chamber, neck size and reload. You'll have to decide how to size your brass. Everybody has different thoughts and ideas, just look at the recent election!!

[RC20]

Man am I confused. Maybe I go about this on too simple a basis.

What were those used cases fired in?

If your factory loads and new Laupau fit fine, then the other cases were blown way out.


And if I was doing this I would get the Hornady Shoulder die set for the comparator and the decent micomreter to go with it (Sear steel, one turn per dial) , see what they are out at the shoulder and if your dies is bumping back at all.

Hard cam over you should get .005 to .010, maybe as much as .015.


I am missing all this comparing head space gauges and chamber measurements.

The rest is some kind of exotic method I have not heard of and sounds excessively complicated

So far we don't know what the should is doing and comparing a case to a gauge is ???????

Maybe I am just old and out of it, but its not the way I have learned.

Measure a case, fire it in the gun, bump it back to what fits seeing what's going on with the Hornady should adaptor for that caliber.

[Robinhood]

Robinhood, I may end up going this route depending on what Forster tells me when I call them tomorrow. Interesting you like 0.007 clearance. I would have thought that was a lot. I thought the difference between go/no-go was about 0.045.


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I was not saying I like .007" clearance I was saying that the difference in the datum on a no go and a go gauge for a 308 is about .007. You can set your headspace to maximum and after the first firing just bump the shoulder back .001" or .002" and It will shoot just like your headspace was .007 shorter.

If your barrel is chambered per SAAMI specs, and you decide to go short on your case shoulder you risk bumping the face of the bolt against the breach. If you want to run it long then you start to hang a lot of case out of the breach. The case should hang out of the barrel about .125. The depth of the counter bore on the bolthead is about .130. Im going off of a poor memory so measure your own but you will see that it is a bout .005 difference +/-.

[yew plucker]

I did EXACTLY the same thing and got the exact same results. Virgin brass chambers perfectly, once fired brass from any other chamber has to be sized with a good amount of cam over. I even turned 15 thou off the bottom of my die just for that purpose. Some lake city brass won't even size down enough to use, so I throw them in the recycle bin.

I also noticed that I am getting higher chamber pressures with old reliable load data. I have had to tame my loads down a bunch to keep from getting erratic performance.

I am a believer in a tight chamber. It should extend the life of your brass. Once you adjust your load data down a bit, everything should work very well.

[m12lrs]

I always set my barrel down tight on the go gauge but i am begining to wonder about that. What i have read is that the no go is really set up at the maximum saami spec and the field gauge is the one that is too long.

So it seems to me you could make you chamber a little (very little) longer without having a problem. We all know factory brass shoulders are much shorter than SAAMI spec and as reloaders.we are measuring our shoulders on fired brass and set our dies up for a .001 shoulder bump anyway. So after fireforming chamber length really doesn't matter within reason.

[Texas10]

I suppose an argument could be made that setting up the chamber on the long side of spec, i.e., bolt closes stiff on the no-go gage, will result in fire formed brass with an increased internal capacity and thinner walls, resulting in lowered pressures and more room for powder. Maybe some one here has actually experimented with that idea and can add some data and conclusions.

And if your dies are set up to only move the brass enough to chamber the round again, brass life might not be too adversely effected.

The only "fly in the ointment" that I can see with that idea is this; what if the actual chamber diameter is on the large side of spec. If that's the case, you're going to be moving more brass with each sizing with resulting short brass life unless you have a die custom made to your chamber spec using your fire formed brass.

In the end, the relationship between your chamber and your die is what matters. And if you've exceeded the dies capability to adjust to your chamber, you may need to adjust your chamber to your die or buy another brand of die to get the performance you need.

[m12lrs]

Or just not go so tight on the go and still not close on the no go.

[RC20]

I suppose an argument could be made that setting up the chamber on the long side of spec, i.e., bolt closes stiff on the no-go gage, will result in fire formed brass with an increased internal capacity and thinner walls, resulting in lowered pressures and more room for powder. Maybe some one here has actually experimented with that idea and can add some data and conclusions.

And if your dies are set up to only move the brass enough to chamber the round again, brass life might not be too adversely effected.

The only "fly in the ointment" that I can see with that idea is this; what if the actual chamber diameter is on the large side of spec. If that's the case, you're going to be moving more brass with each sizing with resulting short brass life unless you have a die custom made to your chamber spec using your fire formed brass.

In the end, the relationship between your chamber and your die is what matters. And if you've exceeded the dies capability to adjust to your chamber, you may need to adjust your chamber to your die or buy another brand of die to get the performance you need.

I don't see the miner brass difference making any difference in pressures. Case variance is more than that (assumes same case used). Different mfs and how thick the inteiroi is would make some difference. Had a discussion with someone on that, they said it was irrelevant (top shooter of some kind)

You chamber difference will be the shoulder, once its pushed out and if you minimum bump it, then that is not an issue

I have shot a lot of Model of 1917 30-06, its normal head space is almost to a field reject point (they did not care, they wanted the gun to shoot in mud and hot combat with carbon build up)

I segregate the brass now, but before I did that it was a non factor before (other than it would crack a bit sooner).

I haven't had any crack since I gave them their own fodder and do the minimum bump back per that case not the SAMMI spec Savage cases (now, I had a Sako at one time that was co shot with the 1917x)

Yes they also do some case sizing but its pretty small.

I will get some measurements next time I shoot the 1917.

As this is a work in progress the reloading has been adapting. Minimum shoulder bump back was one step over the old methods, annealing is another, I now have a neck sizer only die (which works really well) instead of the ball in the sizing die.

There are other things to do but I am doing one at a time as I get a system down and comfortable with it, then look at what seems to be the next step for either brass longevity (minimum bump back and annealing) or better accuracy (neck sizer)

Part of that is I need to keep up with my shooting needs and a significant change can disrupt the output.

[m12lrs]

I don't see the miner brass difference making any difference in pressures. Case variance is more than that (assumes same case used). Different mfs and how thick the inteiroi is would make some difference. Had a discussion with someone on that, they said it was irrelevant (top shooter of some kind)

You chamber difference will be the shoulder, once its pushed out and if you minimum bump it, then that is not an issue

I have shot a lot of Model of 1917 30-06, its normal head space is almost to a field reject point (they did not care, they wanted the gun to shoot in mud and hot combat with carbon build up)

I segregate the brass now, but before I did that it was a non factor before (other than it would crack a bit sooner).

I haven't had any crack since I gave them their own fodder and do the minimum bump back per that case not the SAMMI spec Savage cases (now, I had a Sako at one time that was co shot with the 1917x)

Yes they also do some case sizing but its pretty small.

I will get some measurements next time I shoot the 1917.

As this is a work in progress the reloading has been adapting. Minimum shoulder bump back was one step over the old methods, annealing is another, I now have a neck sizer only die (which works really well) instead of the ball in the sizing die.

There are other things to do but I am doing one at a time as I get a system down and comfortable with it, then look at what seems to be the next step for either brass longevity (minimum bump back and annealing) or better accuracy (neck sizer)

Part of that is I need to keep up with my shooting needs and a significant change can disrupt the output.

Here is an interesting.solution to the neck tension adjustment scenario

Whidden full length non bushing sizing die and his expander ball kit

http://www.whiddengunworks.com/produ...kits-and-sets/

http://www.whiddengunworks.com/product/sizer-die-only/

[mjphawk]

Thanks all here for the advice. Finally got some time off work to spend checking things. Turns out my old FL die was not bumping should back enough.

My new Redding body die did the trick.
Go Gauge: 1.620 (1.630 printed on gauge)
Redding Body die with full cam and standard she'll holder: 1.614"
Body die with +0.006" competition she'll holder gets me to exactly 1.620" with easy bolt close.

Going to leave it there and see how it shoots. Easy enough to move later.

Also sending my other FL die back for inspection.



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[RC20]

My brother picked up some stuff and got a free Lyman M die as par of an order package , gave me one.

I like it. Not sure its the same as sort of the the super fancy neck tension stuff, but it works nicely and a lot less stress on the cartridge then the expander ball (removed now) .

I ran the new Lapua I had though it as it tend to have about 14 really tight case necks, well as bunch of resized brass.

Significant improvement in uniformity of seating a bullet and the new Lapua.

Resized ones operation was very smooth.