Go-No Go dimensions question

Fastestmanalive

Fastestmanalive

Regular
Rating - 100%
5   0   0
Location
Quebec City
Howdy,

I bought a set of gauges to set the headspace on a new savage prefit in 30-06. The set is from Clymer, got them from Brownell’s. On the package, it’s written 2.0487’’ / 2.0547’’ which makes perfect sense for Saami’s specs for th Odd-six.. However, when I measured them at the datum with the Hornady headspace comparator (0.375) bushing, I get 2.040’’ for the Go gauge and 2.046 for the No Go. I understand my mastercraft caliper and the Hornady comparator are not professional tools, but this seems quite off. Using the same tool, I have unfired Lapua cases that are 2.0415-2.0420’’.

Sorry if this is a dumb question, but what am I missing? I already set the headspace on the rifle with them, just a little concerned here.

Thanks.
 
If you set the headspace so you can barely feel the stripped bolt close on the go gauge - you have it perfectly set for minimum headspace. Trust your steel gauges.
 
Your absolute best gauge for setting your reloading die is your chamber and the bolt in your rifle. No one else has an identical one - the "comparators" can only be built to an "average" dimension, with plus/minus manufacturing tolerances. As the man said, "trust your steel gauges" when installing the barrel. I would add to trust your bolt and chamber to set up your sizing die.
 
Thanks guys.

Probably overthinking this. I am 100% confident I set the headspace right based on the gauges. Was just puzzled by the measures I took with the comparator.

Rifle is ready to send’em then.
 
If you use your steel gauges to set the headspace and adjust your sizing die to match your chamber you have your rifle set to a 'standard' and you should be able to load successfully.

If you set your headspace using a fired case and your sizing die, you will be able to load successfully but your rifle may not actually be set to a 'standard'.
 
Of course,if you happen to have a set of steel gauges which are under-sized, your rifle may not be set to a standard either. If the barrel is set using the gauge and the bolt is difficult to close over new brass, then either the brass or the gauge is not within spec. By the way, I won't have a no-go gauge in the shop; it just gives me another opportunity to make a mistake by picking up the wrong gauge.
 
I have a couple of no go gauges obtained some where.. but I marked them with red paint... I now only buy go gauges if I need them
 
Leeper said:
Of course,if you happen to have a set of steel gauges which are under-sized, your rifle may not be set to a standard either. If the barrel is set using the gauge and the bolt is difficult to close over new brass, then either the brass or the gauge is not within spec. By the way, I won't have a no-go gauge in the shop; it just gives me another opportunity to make a mistake by picking up the wrong gauge.
Click to expand...

Yes, I am just confused why a company making precision tools and gauge so critical to safety would make them undersized while they are marked as SAAMI dimensions on the packaging. Will drop Clymer an email see what they say.
 
Fastestmanalive said:
Yes, I am just confused why a company making precision tools and gauge so critical to safety would make them undersized while they are marked as SAAMI dimensions on the packaging. Will drop Clymer an email see what they say.
Click to expand...

Try measuring using a depth micrometer, not calipers... see if there is a difference.
 
Hole tolerances of your comparator bushing will affect where it will contact on the shoulder of the headspace gauge as well.
 
Fastestmanalive said:
Howdy,

I bought a set of gauges to set the headspace on a new savage prefit in 30-06. The set is from Clymer, got them from Brownell’s. On the package, it’s written 2.0487’’ / 2.0547’’ which makes perfect sense for Saami’s specs for the Odd-six.. However, when I measured them at the datum with the Hornady headspace comparator (0.375) bushing, I get 2.040’’ for the Go gauge and 2.046 for the No Go. I understand my mastercraft caliper and the Hornady comparator are not professional tools, but this seems quite off. Using the same tool, I have unfired Lapua cases that are 2.0415-2.0420’’.

Sorry if this is a dumb question, but what am I missing? I already set the headspace on the rifle with them, just a little concerned here.

Thanks.
Click to expand...

Not a dumb question. I have GO and NOGO for -06, and a few other calibers. I also own the Hornady L-N-L gauge. On your package the dimensions are marked 2.0487" / 2.0547", and as it is listed to the ten-thousandth of an inch, it tells you the precision. It appears like Clymer makes their GO to chamber min spec. and the NO GO is 0.004" shorter than chamber max.

I use my GO and NOGO gauges to calibrate my L-N-L gauge. For -06 I put the GO in the gauge and "0" (Zero) my Mastercraft vernier. Now when I measure fired cases, I know how much longer or shorter they are from that standard.

Every gauge has to be calibrated to a standard that is held to a higher standard than the gauge, basic metrology. Therefore, zeroing your L-N-L to a GO or NOGO, then measuring a case, increases the precision of the measurement.

In most instances, I just "0" the vernier on a fired case, check a few more to check for consistency, and then adjust my FL die (with a set of Redding Competition shellholders) for the desired setback.

Just FYI I measured my GO/NOGO gauges.

i: Manson -06 GO: 2.039 (2.0487 +0.0005 -0.000)
ii: Herters -06 GO: 2.0365
iii: Herters -06 NO GO: 2.042 (the price on it is $3.97 from their Waseca store.)

Manson and Herters probably made to different specs.

Absolute measurement not precise, but because I have GO and NOGO gauges, I have a standard for comparison or calibration.

For 22-250 the datum is 0.347". the L-N-L gauge does not come with a 0.347", it comes with a 0.350". So, with the 0.350 in my L-N-L my 1.5749 GO measures 1.5625 and the 1.5799 NO GO is 1.567". I'm satisfied, with my gauge, I can measure the difference and I'm only 0.0005" out.

Your new Lapua brass measure between GO and NO GO, sounds good to me.

On your L-N-L you measured a difference of 0.006" between your NO GO and GO, (2.0547 - 2.0487 = 0.006), perfect.

Addendum: If one looks at my numbers, the actual lengths that I measure, they are a bit off spec. (almost 0.010"). I've included a picture of my .375 bushing. The edge on my bushing is no longer sharp, it is worn from use. The Hornady bushings are aluminum, hard anodized to resist wear. I've used this bushing quite a bit, I think I've owned and used it for 10 years. When I measure I give the brass a little wiggle to make sure it is seated. And, all these little wiggles have added up to some wear. Because I use it for comparison measurements, it still does what I want it to do. IOW, I compare the length of a fired brass to the length of my GO gauge. I compare the length of a FL resized brass to a fired brass, etc. So, when I record the measurement, I just list the deviation from the reference.

Examples: > FL die mated with 0.006 shellholder to set shoulder back 0.003", or fired case is 0.002" longer than Manson GO gauge.

ImQd9mWl.jpg
 
Last edited:
It is unusual but not unheard of, for brass to be longer than the "go" gauge. Generally speaking, if it is longer than the gauge, either the brass is too long or the gauge is too short. The "go" gauge should be chamber minimum and should be equivalent to cartridge maximum. Plainly, this is not the way things always are.
 
Leeper said:
It is unusual but not unheard of, for brass to be longer than the "go" gauge. Generally speaking, if it is longer than the gauge, either the brass is too long or the gauge is too short. The "go" gauge should be chamber minimum and should be equivalent to cartridge maximum. Plainly, this is not the way things always are.
Click to expand...

Each caliber has it's own specifications and tolerances, and generally speaking on rimless calibers the difference between chamber min. and chamber max. is 0.010" @ the datum. And, as you stated, generally speaking the GO gauge is made to min chamber headspace. The bolt should close, without any resistance on a GO gauge. And again, generally speaking, a FIELD gauge is made to chamber max headspace. I've looked at quite a few specs, and again, generally speaking, the NO GO is half way between the GO and FIELD. Most sets do not come with a FIELD, so the NO GO is app 0.005" longer @ datum than the GO, and the GO is @ chamber min.

However the correlation between the chamber and ammunition seems to be a per caliber thing.

For the -06, chamber min/max @ datum is 2.0487/2.0587, and the cartridge spec is 2.0526 -0.007. IOW. 2.0456/2.0526.

Just a FYI here are the SAAMI specs for the 6.5 Creedmoor.

For the 6.5 CM, chamber min/max @ datum is 1.541/1.551, and the cartridge spec is 1.5438 -0.007. IOW. 1.5368/1.5438.

So, typically for a rimless caliber, cartridge max is about 0.003 > 0.004 longer than chamber min at the datum.

Belted magnums are a horse of an entirely different color. The 300 Win Mag is typical of most belted magnums, and although belted magnums headspace on the belt, SAAMI still lists a measurement @ datum.

300 WM; Cartridge spec @ datum is 2.2700 -0.007, and the chamber min/max is 2.2791/2.2891. And this can lead to issues for the reloader. If the FL die is manufactured to resize to cartridge min. (and typically they are) and your chamber was near max @ datum, again this is common, the shoulder would be set back about 0.025". When I was reloading for my 350 RM, I was able to buy a +0.022" shellholder that they had in stock.

Which is the long winded way to say that measuring tools are necessary, and I would not want to reload without having a GO gauge (the standard), a L-N-L Hornady gauge for measuring, and a SAAMI drawing to make sense of it all.

Nitro
 
You must log in or register to reply here.
Back
Top Bottom