swd
Silver $$ Contributor
New cases are usually quite short. A few years ago I checked a friends new 6.5 Creed brass and they averaged .008" short of go with a few as much as .012".
Taped Go-Gauge / No-Go
- Thread starter Italianusmc_ny
- Start date
If you are putting a new expensive barrel on your rifle I would never use "soft" masking tape on the back of a GO gauge that is .0055 in thickness. I would use something harder that was approximately .003 in thickness and make the headspace tighter.
I have old rifles that fail a Field gauge and they can be safely fired with reduced loads. And I have used many methods to check headspace on the old milsurp rifles I collected.
Most rifles have .010 between the GO and Field gauges. "BUT" the NO-GO gauge is the max headspace you want for setting up a new barrel. And I would never use soft masking tape to set up headspace.
I have old rifles that fail a Field gauge and they can be safely fired with reduced loads. And I have used many methods to check headspace on the old milsurp rifles I collected.
Most rifles have .010 between the GO and Field gauges. "BUT" the NO-GO gauge is the max headspace you want for setting up a new barrel. And I would never use soft masking tape to set up headspace.
- GO: Corresponds to the minimum chamber dimensions. If a rifle closes on a GO gage, the chamber will accept ammunition that is made to SAAMI maximum specifications. The GO gage is essential for checking a newly-reamed chamber in order to ensure a tight, accurate, and safe chamber that will accept SAAMI maximum ammo.
- NO-GO: Corresponds to the maximum headspace we recommend for gunsmiths’ chambering new bolt-action rifles. This is not a SAAMI-maximum measurement. If a rifle closes on a NO-GO gage, it may still be within SAAMI specifications, or it may have excessive headspace. To determine if there is excessive headspace, the chamber should then be checked with a FIELD gage. The NO-GO gage is a valuable tool for gunsmiths’ reaming new chambers, in order to ensure tight and accurate headspace.
- FIELD: Corresponds to the longest safe headspace. If a rifle closes on a FIELD gage, its chamber is dangerously close to, or longer than, SAAMI-specified maximum chamber size. If chamber headspace is excessive, the gun should be taken out of service until it has been inspected and repaired by a competent gunsmith. FIELD gages are slightly shorter than the SAAMI maximum in order to give a small safety margin.
Clear scotch tape is 2.5 thousandths.
Painter’s tape is not commonly used. Any tape thicker than the difference between go/no-go defeats the purpose.
I installed a CBI on my Savage this spring. Set headspace as tight as I could and still have the go gauge have no perceptible bolt drag on closure. 2.5 mil cellophane tape won’t even let the bolt start.
My thinking is that I’m minimizing the degree to which any brass that I didn’t size (i.e. factory) is being worked.
My thinking is that I’m minimizing the degree to which any brass that I didn’t size (i.e. factory) is being worked.
^^^^^this is the ticket. You don't have to worry about crushing the shimstock material if you are the type (not me) to have a Gorilla grip. Kinda like the lady that tightens the nuts on the Savage barrels.
I wonder if that was Effie Sullivan?
jelenko
Gold $$ Contributor
Gorilla tight: You tighten the screw until the threads start to smoke, and then give it two more full turns.
There is zero issue using cellophane tape on the go gauge for the no go. There is not even an issue with not fully closing on a go gauge if the brass fits.
The downside to tight headspace is when you want the flexibility to use any brass or ammo in it. There is less downside to the brass since you can size it before using it if needed. That said, I would not chamber a barrel for someone else that was that tight.
Now if we can't feel the difference between a light start on a taped go gauge vs heavy pressure when forcing it, then maybe we shouldn't be headspacing our own barrels.
The downside to tight headspace is when you want the flexibility to use any brass or ammo in it. There is less downside to the brass since you can size it before using it if needed. That said, I would not chamber a barrel for someone else that was that tight.
Now if we can't feel the difference between a light start on a taped go gauge vs heavy pressure when forcing it, then maybe we shouldn't be headspacing our own barrels.
I have seen posting at Savageshooter where they set the headspace tighter than the GO gauge.
Their next posting is "Help my full length sized brass will not chamber".
If your die won't bump the shoulder back shorter than the chamber headspace what good your overly tight headspace. This turns your GO gauge into a NO-GO gauge with no wiggle room.
There is a BIG difference between headspace that is a little tight vs a lot tight. A little tight is usually okay. I don't know what Savage Shooters do, but on my second to last chamber job I wound up a little tighter that I wanted. The bolt would start on a go gauge but not completely close. We seem to lose about .001" from tight on the lathe vs final barrel tightening.
Rather than re-indicate the barrel in the lathe and try to get another .0005" of chamber depth, I checked to see if the brass fit. The bolt closed fine on the brass so I left it as is. I have since put 450 rounds though the barrel with no issues.
I suppose if I was doing a Savage and it was a simple matter of loosening the barrel nut and backing out the barrel a tiny bit I would do that. But I am not going to re-indicate a barrel in again just to gain another .0005 to .001" of headspace when my brass fits.
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If your dies and your brass will chamber the round always, then the actual headspace can go well below minimum. The point of the spec is to ensure compatibility via standardization.
I personally find it to be one of those “price is right” things—you want to be as close as you can without going over. Thus I strive for the smallest headspace that closes the go gauge.
It just happens that this approach also causes my sizer to give nearly perfect bump just exactly when the shell holder touches the die.
Life is just easiest with headspace as close to minimum as you can get without going too far.
I personally find it to be one of those “price is right” things—you want to be as close as you can without going over. Thus I strive for the smallest headspace that closes the go gauge.
It just happens that this approach also causes my sizer to give nearly perfect bump just exactly when the shell holder touches the die.
Life is just easiest with headspace as close to minimum as you can get without going too far.
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divingin
Gold $$ Contributor
I don't think that's correct. Case stretch occurs when the case is driven forward by the firing pin, the case neck grabs and holds the chamber, and the case head is blown back against the breech.
If you can hold the case head against the breechface (either a tight extractor, false shoulder, whatever) blowing the shoulder forward will not cause any thinning of the case body. The shoulder moves as the unsupported neck area expands to the shoulder of the chamber (to placate Guffey, "the shoulder is reformed further forward", rather than "the shoulder moved".)
Why would the case not get into the die as far? Isn't the distance the case enters the die controlled by your die/case holder relationship? I'm pretty sure I reformed a .30-06 case into a 308 as an experiment once (don't recall if I trimmed first or just went for it.) That would be like the ultimate stretched brass.
Case head seperation occurs when the headspace has been set back too far too many times.. when theires excessive headspace that case grows longer to fill the chamber.. that growth comes from just above the case head.. (the 200 datum line.. ) which in turn if done too many times will cause separation at that 200 line.. as far as the die sizing problem goes say your using a standard fl die.. its designed to bump the shoulder back to a sammi standard length.. so you decide your going to set your headspace .010 longer.. but you only want to bump the shoulde back .002 .. that leaves .008 of the base not getting sized that normally would.. that .008 can cause problems chambering and extracting the round.. because its not sized.. hence the need for a small base die .. i could be all wrong about this.. im a rookie
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