Headspace question

[TedH]

I obtained a replacement bolt for the Model 70 basket case 30-06. Full length resized brass, as well as a factory loaded cartridge, chamber and allow the bolt to close easily. With a Forster no-go gauge in the chamber the bolt will just close, but it takes some effort. From what I'm reading the no-go gauge is the maximum end of spec. I know ideally the bolt would not close at all on the no-go, but to close with drag on it would indicate it to be a safe, but generously sized chamber. Is this thinking correct?

I also checked my Remington 700, and the bolt will not close at all on it, but my CMP M1 Garand will just tightly close on it, but again takes considerable effort.

[Rockrat]

Does sound like you are close to max spec on headspace. try getting an automotive feeler gauge set and take a pair of sharp scissors and cut a piece of the .003" blade to fit in the bolt face flat and then try to close on a live round. I would take a factory round and use a set of wire strippers and your press, to pull the bullet and save the powder and then try to just use the primed case. See how the bolt closes.

[GunnyMack]

You are at the max spec for the chamber.
Two options
1 set the barrel back a full turn ( if it has iron sights) or even a half turn and chase the chamber. Either way you will need a finish reamer. Of course a lathe , action wrench and barrel vise are needed to do this.
2 ream to the other chambering you mentioned previously. You can do this by hand without a lathe. Go slow and LOTS of oil. After you get the correct headspace polish the chamber with 400 grit.

[Pat C]

On a stripped bolt should not close with one finger pressure.
Sounds like your apply force to get it to close which can ruin headspace gauge .Be careful.

[TedH]

On a stripped bolt should not close with one finger pressure.
Sounds like your apply force to get it to close which can ruin headspace gauge .Be careful.

Perhaps I didn't word that correctly. I'm not using Bubba force on the bolt. Just enough to feel the resistance with the stripped bolt.
As another measure, I added a single layer of masking tape to the rim of the head space gauge, and the bolt would not close on it with light pressure as you described.
That tells me that the chamber is at the max end of spec.
Ideal? No, but should be safe. I will only neck size brass or back a full length sizer out about 1/8 turn to not overwork the cases.

[JB]

I obtained a replacement bolt for the Model 70 basket case 30-06. Full length resized brass, as well as a factory loaded cartridge, chamber and allow the bolt to close easily. With a Forster no-go gauge in the chamber the bolt will just close, but it takes some effort. From what I'm reading the no-go gauge is the maximum end of spec. I know ideally the bolt would not close at all on the no-go, but to close with drag on it would indicate it to be a safe, but generously sized chamber. Is this thinking correct?

I also checked my Remington 700, and the bolt will not close at all on it, but my CMP M1 Garand will just tightly close on it, but again takes considerable effort.

It sounds like excessive headspace for sure. Perhaps more than you think if you didn't remove the extractor before checking the headspace. Ideally you should remove the extractor so that it doesn't cause any interference with the gauge.

[Pat C]

If stripped bolt with finger pressure has felt resistance with No Go by itself it's perfectly fine. Ideally the bolt should lack just a little before fully locked on NO GO. But if heaspace is toward upper end it may be harder to feel .

There is only .004 difference between go and no go.
Remember there is a field reject that's. 008 over go.

An accuracy build most would like to see it just close over go .
But if your loading for this you'll never see difference.

[JRD]

The headspace and NO GO gauges bring up a subject that is one of my pet peeves from the industry.

This is not directly related to Ted's original question on the feel of his bolt over a NO GO gauge.

In SAAMI specs there is a MIN and a MAX headspace. For 30-06 and many bottleneck rifle cartridges, there is a .010" difference from MIN to MAX.

A GO headspace gauge is at SAAMI MIN and everyone agrees there.

NO GO gauges are where the discrepancy comes in because NO GO is not a SAAMI standard and many companies have their own flavor of what they call NO GO. Also bear in mind that NO GO is intended as the high headspace limit for a NEW gun, and that a new gun can be right at the high limit of the NO GO gauge and still be safe and within SAAMI MAX. A brand new gun may have it's headspace gun grow by a .001" or two as the locking surfaces marry together from firing and working the action. The change in headspace is less of a factor in custom guns where actions are blueprinted and bolt lugs are lapped, but in mass production rifles, there is always some degree of skewness or lack of flatness between locking surfaces.

A FIELD headspace gauge is at SAAMI MAX and represents what is considered the safe limit on when a gun in the field should be taken out of service.

Commercial NO GO headspace gauge makers don't always mark their gauges with the exact dimension that the gauge is. Is it MIN+.003? Min+.006? etc...
Firearm manufacturers also have their own specifications for NO GO gauges for making new guns. Some bolt gun makers who use screw on barrels that use a lock nut, may put the bolt in place with a GO gauge in the chamber, and tighten the barrel down to stop on the GO gage, and then tighten the lock nut. They may then use a +.002 NO GO gauge because they want to run their new rifles to the low side of SAAMI for better accuracy potential.

Other makers who rely on tolerance stackup and tightly control depths between the bolt, receiver, and barrel may uses a +.005" or +.006" NO GO gauge and rely on the tolerance stack between those parts to always yield a headspace between SAAMI MIN (GO) and their chosen high limit NO GO.

Still others who may do things how Winchester and Remington did it years ago would short chamber barrels and used a finish chamber reamer that was driven by a mandrel running down the bore, and closed the bolt on that cutting reamer which cut the chamber depth to match that bolt. This is likely how Winchester did it when they built Ted's rifle. Also note that most of those old guns had the serial number electric penciled onto the bolt body to keep bolts matched up with their respective receiver in the factory.

Ultimately Ted, depending on what Forster used on their NO GO headspace gauge that you bought, the chamber still may be within SAAMI MAX which would be within a safe FIELD headspace. If the dimension isn't marked on the gauge, consider asking Forster what they use for their actual dimension.

(I've also heard from some industry friends who's companies have metrology labs capable of inspecting gauges down to the .0001", and have found some commercial gauges deviating by as much as .002" from what they were supposed to measure. )

If you can close the bolt very snugly on a commercial NO GO, it could still be safe to shoot. If you have the Hornady headspace comparator for your calipers you could always measure a factory round, fire the rifle (perhaps remotely from sandbags if you want to be cautious), and then measure the fired brass to see how much it grew. If you have another 30-06 you could always do the same test as a comparison to see how the case expansion compares to your new rifle.

I typed a bunch here and many may not comprehend some details, but I tried to articulate my point. There's lot of people in the industry who don't get what I described here, never mind folks on the internet.

[Tycer]

I typed a bunch here and many may not comprehend some details, but I tried to make articulate my point. .

Ya done good. Very well articulated. Thanks!

[TedH]

If the dimension isn't marked on the gauge, consider asking Forster what they use for their actual dimension.

Thank you for the detailed explanation. Very helpful.
This Forster is marked 2.0547. I guess i need to find out what SAAMI max is.

[JRD]

SAAMI MIN-MAX is 2.0487”-2.0587” for 30-06 Springfield.

Thus Forster NO GO is MIN+.006”. You’ve got another .004” before you get to MAX or FIELD.

Headspace on the low end of the range is usually preferred. Your brass will stretch less and in theory the cartridge is a tighter fit in the chamber for better alignment (for accuracy).

If your rehabbed rifle is just at NO GO, you may not be past field after the locking surfaces marry together.

It may be worth trying as is like I described. If the shoulder isn’t too bad, then dedicate brass to this rifle and don’t set the shoulder back to MIN.

[TedH]

SAAMI MIN-MAX is 2.0487”-2.0587” for 30-06 Springfield.

It may be worth trying as is like I described. If the shoulder isn’t too bad, then dedicate brass to this rifle and don’t set the shoulder back to MIN.

That's my plan then. I will neck size for now until such time as they may need the shoulder bumped back.

[AJMD429]

The headspace and NO GO gauges bring up a subject that is one of my pet peeves from the industry.

This is not directly related to Ted's original question on the feel of his bolt over a NO GO gauge.

In SAAMI specs there is a MIN and a MAX headspace. For 30-06 and many bottleneck rifle cartridges, there is a .010" difference from MIN to MAX.

A GO headspace gauge is at SAAMI MIN and everyone agrees there.

NO GO gauges are where the discrepancy comes in because NO GO is not a SAAMI standard and many companies have their own flavor of what they call NO GO. Also bear in mind that NO GO is intended as the high headspace limit for a NEW gun, and that a new gun can be right at the high limit of the NO GO gauge and still be safe and within SAAMI MAX. A brand new gun may have it's headspace gun grow by a .001" or two as the locking surfaces marry together from firing and working the action. The change in headspace is less of a factor in custom guns where actions are blueprinted and bolt lugs are lapped, but in mass production rifles, there is always some degree of skewness or lack of flatness between locking surfaces.

A FIELD headspace gauge is at SAAMI MAX and represents what is considered the safe limit on when a gun in the field should be taken out of service.

Commercial NO GO headspace gauge makers don't always mark their gauges with the exact dimension that the gauge is. Is it MIN+.003? Min+.006? etc...
Firearm manufacturers also have their own specifications for NO GO gauges for making new guns. Some bolt gun makers who use screw on barrels that use a lock nut, may put the bolt in place with a GO gauge in the chamber, and tighten the barrel down to stop on the GO gage, and then tighten the lock nut. They may then use a +.002 NO GO gauge because they want to run their new rifles to the low side of SAAMI for better accuracy potential.

Other makers who rely on tolerance stackup and tightly control depths between the bolt, receiver, and barrel may uses a +.005" or +.006" NO GO gauge and rely on the tolerance stack between those parts to always yield a headspace between SAAMI MIN (GO) and their chosen high limit NO GO.

Still others who may do things how Winchester and Remington did it years ago would short chamber barrels and used a finish chamber reamer that was driven by a mandrel running down the bore, and closed the bolt on that cutting reamer which cut the chamber depth to match that bolt. This is likely how Winchester did it when they built Ted's rifle. Also note that most of those old guns had the serial number electric penciled onto the bolt body to keep bolts matched up with their respective receiver in the factory.

Ultimately Ted, depending on what Forster used on their NO GO headspace gauge that you bought, the chamber still may be within SAAMI MAX which would be within a safe FIELD headspace. If the dimension isn't marked on the gauge, consider asking Forster what they use for their actual dimension.

(I've also heard from some industry friends who's companies have metrology labs capable of inspecting gauges down to the .0001", and have found some commercial gauges deviating by as much as .002" from what they were supposed to measure. )

If you can close the bolt very snugly on a commercial NO GO, it could still be safe to shoot. If you have the Hornady headspace comparator for your calipers you could always measure a factory round, fire the rifle (perhaps remotely from sandbags if you want to be cautious), and then measure the fired brass to see how much it grew. If you have another 30-06 you could always do the same test as a comparison to see how the case expansion compares to your new rifle.

I typed a bunch here and many may not comprehend some details, but I tried to articulate my point. There's lot of people in the industry who don't get what I described here, never mind folks on the internet.

That ALL matches what I've been taught and told and read (and mostly forgotten). Thanks for clarifying and educating. I kinda remembered some of that but would never have been able to summarize it so well.

[Glenn]

Get yourself a set of Redding Competition Shellholders (https://tinyurl.com/LittleDuke45). They are +.002, +.004, +.006, +.008 and +.010 thicker than standard shellholders, so you can adjust your FL size die to contact the shellholder and not set the shoulder back too much for your chamber.
Glenn

[TedH]

Get yourself a set of Redding Competition Shellholders (https://tinyurl.com/LittleDuke45). They are +.002, +.004, +.006, +.008 and +.010 thicker than standard shellholders, so you can adjust your FL size die to contact the shellholder and not set the shoulder back too much for your chamber.
Glenn

Thanks, that's a good idea.