Setting headspace

[4runnerman]

Looking for advice. Got a Savage 6MMBR. On my 4th Barrel now. I have the Go, NoGo Gauges. Switched barrels here about 2 months ago. I have a 100 lot of new Lapua Brass. They have been loaded 7 times and I have 4 case head seperations ( not complete seperations,, just 3/4 around ejected fine). Every other time I have switched barrels I get about 18 loads out of the brass before I get split necks ( never case seperation). This is not a new barrel, just a older one that I put back on for the heck of it. My question is- When installing new barrel
A- Do you tighten till no go gauge does not close, but go gauge does

B- Same except keep tightening till go gauge closes, but just does. ( not with resistance though).

Right now I am tightening till no go just startes to not close, but go gauge does.
Is there ( Im sure) a area in there where just because no go does not close that it should still be tightened just a smidgen more. Hence making go gauge still close but tighter?. Should one go to were go gauge does not close and start backing off from there till it does?.

C- Did I just get one bad batch of Lapua Brass-Doubtfull but a possability.

Hope I explained this good enough.
I think what I am asking is- Just because no go gauge does not close , but go does, Is my headspace still to much and should be a few .000's tighter.

 

[tobnpr]

You're over-complicating it...

This:

On the average bolt rifle, you establish correct headspace by lathe-turning the shoulder on the barrel. However, with the Savage, all you have to do is remove the firing pin and ejector from the bolt, insert a GO Headspace Gauge into the chamber, screw the barrel into the receiver until the gauge bumps up tight against the bolt face, tighten the barrel lock nut and you have a barrel that is set up to minimum headspace. Let’s go through the steps, one by one.

From this:

https://www.brownells.com/.aspx/lid=12578/GunTechdetail/Re_barreling_Your_Savage_Rifle

If you really want to fine tune it, follow the above procedure, load and fire some rounds, check for the largest datum dimension using a headspace gauge like the LNL, and use that to re-set the headspace. Using a go-gauge gives you mimimum SAAMI headspace. Since you reload, you can set it to your exact chamber dimensions.

Caveat: setting your headspace with your fireformed brass may preclude use of factory (SAAMI) ammo...

 

[Jim Watson]

I have never done it but twice, a friend and I rebarrelled our Savage .308s DIY. We screwed the barrels down to contact with the Go gauge and tightened the nuts as tobnpr cites. The Savage board says that will give headspace at minimum + .0015" as the barrel thread loads up.

We have not had any casehead separations.

 

[4runnerman]

tobnpr- Thanks. I did as you mentioned and I did get another, maybe 1/16 turn tighter on the barrel. Will have to wait till next weekend now to see if issue is resolved.

Thanks Jim- I sure hope I got it right this time.

 

[Unclenick]

If you have any machine shops in your area, ask if they have a few square inches of shim stock they can sell you in 0.001" and 0.0005". You can then cut them out into small discs to fit under GO gauge head and see what combination will still let you close the bolt without starting to contact the end. One 0.001"? One 0.001" plus one 0.0005"? A pair of 0.001" pieces? This will tell you how much extra headspace you actually have.

The threads on the Savages are 20 TPI, or 0.050" per turn. That is 7.2° of rotation per 0.001" of barrel adjustment, which is big enough to see easily. You can turn the barrel into contact with the GO gauge, pencil a registration mark on it and the receiver. Then put a second mark 0.0665" further along for the 1.0625" barrels, or 0.0705" further along the 1.125" barrels for each 0.001" shorter you want to make the final headspace. Then remove the GO gauge and turn the registration to the further mark, and tighten the nut. Re-insert the GO gauge and or shims to see where you are.

 

[4runnerman]

Thanks Nick. Will look into it.

 

[WyMark]

No idea, bot for an M2 it was hand tight then back off two clicks as a starting point. That was in 1975, though. Don't know why this thread title made me remember that tidbit.

 

[F. Guffey]

You have a go-gage and a no go-gage. If you adjust the barrel to the go-gage you will have .004" clearance, then there is the argument/out burst as to where the clearance is, between the case head and bolt face or between the shoulder of the case and shoulder of the chamber.

I am the fan of cutting down on all that case travel. I am also the fan of determining where the case stretches. BIG PROBLEM! There is this story about the case, powder and bullet running to the front of the chamber and then stops when the case shoulder collides with the chamber shoulder. Back to big problem, if the case body locks to the chamber there is no place for the case to stretch except between the case head and case body.

I have killer firing pins, by now everyone should know that. I am a case former, I form cases, I measure the length of a case from the shoulder/datum to the case head. I can form cases that are the same identical length of a go-gage. If I want to cut down on all that case travel I need to adjust the length of my chamber shorter than a go-gage. I also form cases that are for short chambers. I form cases that are .017" shorter than the length of a go-gage.

I believe the minimum case length is more important than the go-gage.

F. Guffey

 

[mehavey]

If you adjust the barrel to the go-gage you will have .004" clearance...

Huh? If you just barely close (w/ 'feel') on a GO gauge,
you should have no excess clearance: Minimum headspace.

Am I misunderstanding something ?

 

[F. Guffey]

Am I misunderstanding something ?

Yes you are.

F. Guffey

 

[F. Guffey]

Again, a builder, resourse,. reloader, collector was building a period correct Rock Island 03 for 1911/ He was trying to work with a gun type forum that I considered socially dysfunctional. every time the word 'head space' came up the members got belligerent.

My part in that, I purchased a mill from him, while loading it the subject of head space came up and the difficulty when dealing with the Internet. I explained to him I could check the length of the chamber in an 03 3 different ways without a head space gage.

After loading the mill he handed me a box full of head space gages, must have been 18 gages in the box, most were 30/06. Nice, to me? Not useful except for transfers and standards. I know the head space gage will allow the bolt to close and the no go-gage should not allow the bolt to close. He wanted to know the length of the chamber from the shoulder to the bolt face and he called it head space. I offered to modify one of his go-gages to a go-to-infinity gage, problem, that would not be period correct.

I collect enough tools off the wall, on his bench and in his tool boxes to measure the length of the chamber three different ways with out a head space gage. And we started.

His chamber was .0025" longer than a go-gage, it was .0075" longer than a minimum length/full length sized case. Problem, the Rock Island 03 for the year 1911 had a straight handle. That was the only straight handle he had, I have one that is installed and working in one of my rifles. He has no less than 75 03 bolts, all with bent handles. I have no less than 30, most new replacement old stock. Correcting the chamber length and staying period correct was not an option, I did offer to go thorough his bolts to determine if he had a bolt that would reduce the length of the chamber by at least .0025". I offered to check all of my bolts to determine if I had a bolt that would correct the length of the chamber.

I have gone through 35 bolts looking for a bolt that would change the length of the chamber .001" +/- .0005". He made a few calls looking for a bolt, everyone he talked to wanted to send him a bucket of bolts because they could not determine the effect the bolt had on the length of the chamber. Are they misunderstand something? YES!

He did contact another resource person that had a few straight handle bolts.

I offered to form cases, he owns the only hydraulically operated press I know of. The machine is magnificent, I had a moment of thought, I thought I wanted one so I started collecting parts and pieces. When I checked the valves, shuttles, pistons and relief valves the box contained pneumatics parts that were operated at 2,000 psi. I got over the urge, I have a pump with ceramic pistons that will exceed 2,000 psi for fluid, not air.

F. Guffey

 

[mehavey]

If you adjust the barrel to the go-gage you will have .004" clearance

If you just barely close (w/ 'feel') on a GO gauge, you should have no excess clearance: Minimum headspace.
Am I misunderstanding something ?

Yes you are.

Interesting answer.
Please elaborate.

 

[tobnpr]

^^
I'm not sure- but I think he may be saying in a more elaborate way what I alluded to in my original post. Or, he could be saying something completely different- sometimes I can't quite follow...

Anyway- even with "minimum" SAAMI headspace- as set by the go gauge- there's still "headspace" (loose definition) clearance for most ammo. This allows for variations in factory ammunition (and brass as well) so that the rifle, can chamber any and all of it- as it would be set as if it came from the factory.

Taking off a few thousandths if you can, seems would be the same concept as setting headspace with fireformed brass as I do. Shoulder datum is shorter- less "slop", and brass stretching in the casehead. At least that's what the thought process tells me. Even after FL sizing with .001-.002 shoulder bump, I have light resistance closing the bolt. Tight as a gnat's a***. Haven't tried any, but I'm sure I could not chamber most factory ammo.

 

[mehavey]

Anyway- even with "minimum" SAAMI headspace- as set by the GO gauge,
there's still "headspace" (loose definition) clearance for most ammo.

1. Don't disagree... I find most commercial ammunition measures slightly below GO/Min Headspace dimensions.

2. As to your own chamber (maybe) not accepting commercial ammunition, you might find that statement #1 above helps you out.

 

[Metal god]

4runner :

What I'm not understanding is why this possible .0100 head space difference is causing head separation . I'm fully aware of how head separation happens . I'm not sure why you are having the issue though based on my understanding on how you size your cases .

I have to assume you fired a few rounds through the new barrel then used a comparator or other method to measure the CASE head space . If you are bumping your shoulders back .002 or if memory serves , you like .003 back from your newly installed barrels fire formed cases . you should not be getting any head separations .

Did you make new measurements of your fire formed cases after installing the new barrel or did you just size them the same as you did the last time the barrel was installed ?

 

[4runnerman]

Metal- You are correct all around. With reading your post I have an Idea. I am going to load 100 rounds of my old brass up for this weekend. They have been fired 13 times, but I have pushed other lots to over 20. It should pin point it down to if I did per chance get a bad batch of brass. Lapua-Bad Brass- Those words just don't go together though ya know. My loads are mid range- 28.8 Varget, BR-4 primer and 107 Match Serrias. Gives me about 2850 MV.

Your last statement-Question. Yes I always set my sizing die off of new barrel. Now being my brass was already all loaded per previous barrel, this could have been the issue also. I have read a lot on setting head space off of one of your pcs of brass instead of gauges. Maybe something I will have to look into.

Got to work and started thinking again- First time out with new Bolt Body too.
That should not really make a difference though. Got a Fluted Bolt body from SSS. I did measure about .0018 shorter than my old one.

 

[F. Guffey]

What I'm not understanding is why this possible .0100 head space difference is causing head separation .

possible .0100 head space difference

Originally Posted by Guffey
If you adjust the barrel to the go-gage you will have .004" clearance

Beyond the go-gage is the no go-gage. After that there is the field reject gage. When dealing with the 30/06 chamber my go-gage is .005" longer than a minimum length full length sized case. The no go-gage is .004" longer than the go-gage. The field reject gage is .011" longer than the go-gage and .014" longer than a minimum length/full length sized case.

A reloader can get away with firing short cases in a long chamber, continuing to full length sized cases for long chambers is a bad habit. Again, I am the fan of cutting down on all that case travel. I want to know the length of the chamber and the length of the case. And again and again there are different designs, all receivers are not the same and reloaders are infatuated with bumping the shoulder back .002". If they installed the barrel with a head space gage why do they have to fire a case to determine the length of the chamber from the shoulder of the chamber to the case head?

Originally Posted by Guffey
If you adjust the barrel to the go-gage you will have .004" clearance

F. Guffey

 

[Metal god]

Now being my brass was already all loaded per previous barrel, this could have been the issue also.

How many times have you fired and reloaded the previously loaded brass in the new barrel ?

Do you still have any of the previously loaded rounds ? Have you compared the datum to head measurement before and after firing that previously loaded brass in the new barrel ?

 

[F. Guffey]

Now being my brass was already all loaded per previous barrel, this could have been the issue also.

Have you compared the datum to head measurement before and after firing that previously loaded brass in the new barrel ?

Did he measure the distance from the shoulder/datum to the bolt face of the new chamber? I cut chambers, measure the length of the chamber from the shoulder to the bolt face then size and or form cases to fit.

I am the fan of cutting down on all that case travel. Then there is that thing about stretch and or flow, I know, sounds cryptic.

F. Guffey

 

[mehavey]

...my go-gage is .005" longer than a minimum length full length sized case.

While I think I now understand Guffey, that clearance is highly variable. Case-in-Point...

SAAMI specs for the 308 Win are:
Min Chamber - GO 1.630"
Min/Max Cartridge - 1.627"/1.634"

When sized to absolute SAAMI minimum, a shell case can have 0.003"
clearance to a minimum (GO-Gauged) SAAMI chamber.

In the real world, however, the actual clearance can vary widely depending upon the sizing die, the age/work-hardness of the brass, the lube used, etc, etc....

So no matter what, it's a best practice to size by referencing a fired case (bolt gun) and measuring to a few thou less than req'd to just chamber,