Go gauge alternative?

[hoz53]

View attachment 1031357

that cant be the Guffey Mobile-- there is to much HEADspace in there.

 

[hoz53]

"I dont know what you're doing but I can tell you're doing it wrong. I cant actually show you this headspace science but trust me I know and you dont." F. Guffey

is that a misspelling and it was supposed to be HeadCase??

 

[hoz53]

I see this question asked often. There is a very simple solution when you find yourself without a head space gage.
Just do the math and measure to a known size steel ball seated in the shoulder to the end of the barrel. If you are not able to figure this out, you should not be working on ANYONE's rifle.
Alan

dont know if OP comprehends this but I never thought of that - good idea Thanks

 

[carlsbad]

I see this question asked often. There is a very simple solution when you find yourself without a head space gage.
Just do the math and measure to a known size steel ball seated in the shoulder to the end of the barrel. If you are not able to figure this out, you should not be working on ANYONE's rifle.
Alan

Alan,
I just spent a few minutes on this, and although the trigonometry is quite do-able, it is tedious and hard to correlate to the datum point on a headspace guage unless you have an exceptional drawing of the chamber or gauge. Care to share your formulae? Maybe there is an eloquent simplification that I missed.

Now if you're just using the ball bearing as a comparator to duplicate the headspace in an existing barrel, that is clear, but doesn't require any math.

--Jerry

 

[DaveTooley]

There are many of us who could and have backed into setting the headspace by something other than a steel gage but there are so many ways it can go south for the inexperienced.
Once you have enough experience to make sound judgement calls about what is safe and what is not and your technical skills catch up with your imagination you might even make your own gages. But that's a ways down the road for you.

 

[JohnMill]

I use exact prosecute as dsculley.
great minds--------.

Me too and I don't bother with the no go process anymore. It'll never see a factory load, just weigh everything, measure everything target loads.
dave Tooley makes a real good point above.
The first thought I had when I read this was how much are you trying to save. I still have my first set of G/NG gages. Good as new and they look new.

 

[GenePoole]

Alan,
I just spent a few minutes on this, and although the trigonometry is quite do-able, it is tedious and hard to correlate to the datum point on a headspace guage unless you have an exceptional drawing of the chamber or gauge. Care to share your formulae? Maybe there is an eloquent simplification that I missed.

Now if you're just using the ball bearing as a comparator to duplicate the headspace in an existing barrel, that is clear, but doesn't require any math.

--Jerry

I agree. While it is doable, it is far from trivial. Let's see your math Alan.

 

[mram10]

Just trying to figure out other alternatives. I bought the go gauges, I just want to know about other ways I have heard about.
Dave, How far off is making a go gauge for me?

 

[GenePoole]

Just trying to figure out other alternatives. I bought the go gauges, I just want to know about other ways I have heard about.
Dave, How far off is making a go gauge for me?

I'm not Dave, but I've made my own gauges before. You need a ring gauge the diameter of the datum, which may be more expensive than a go gauge. Also, most ring gauges have a chamfer so you'll have to surface grind it down several thou to get a good sharp edge on which to make your measurement. Not really worth it unless you have a spare ring gauge in the diameter you need, and surface grinder.

 

[paperpuncher]

Just trying to figure out other alternatives. I bought the go gauges, I just want to know about other ways I have heard about.
Dave, How far off is making a go gauge for me?

Ahh when you can snatch the pebble from his hand grasshopper

 

[urbanrifleman]

I use exact prosecute as dsculley.
great minds--------.

Exactly what I do too. Minimum chambers sure do make life easy.

 

[urbanrifleman]

It is as though there are people that need to permission to do anything or they freeze up...

 

[USMCDOC]

that cant be the Guffey Mobile-- there is to much HEADspace in there.

 

[Alan Warner]

Jerry:
Ignore the datum diameter on the angle.
Start with the length at the top of the body and its diameter.(From the reamer drawing)(( you should always do the math from the HS datum diameter to the diameter @ the top of the body
because SOME reamer makers fu-- up a lot!)) Draw the shoulder angle and set(draw in) the selected ball into the shoulder.
Find the distance from the top of the body to the center of the ball. (Do the trig) Add (or subtract) to that the radius of the ball. Now, subtract that from the body length
and you have a number to the bolt face.
I have an Excell program written that you can plug in the numbers.. I'll find it and post tomorrow.

This is how I qualify every top insert I make for the dies.

Alan

 

[JRS]

Jerry:
Ignore the datum diameter on the angle.
Start with the length at the top of the body and its diameter.(From the reamer drawing)(( you should always do the math from the HS datum diameter to the diameter @ the top of the body
because SOME reamer makers fu-- up a lot!)) Draw the shoulder angle and set(draw in) the selected ball into the shoulder.
Find the distance from the top of the body to the center of the ball. (Do the trig) Add (or subtract) to that the radius of the ball. Now, subtract that from the body length
and you have a number to the bolt face.
I have an Excell program written that you can plug in the numbers.. I'll find it and post tomorrow.

This is how I qualify every top insert I make for the dies.

Alan

Wish I could "like" that response 100 times

 

[GenePoole]

This took me about an hour, but the trig works out. Pleas excuse the crudity of this model; I didn't have time to paint it or build it to scale:

So here's the final equation (it could probably be simplified a bit):

Where:

HS = Headspace (per SAAMI)
R_ball = Radius of ball bearing
SA = Shoulder Angle
DL = Datum Length (per SAAMI)

 

[Alan Warner]

This is less complicated.
subtract the .3571 from the shoulder /body junction and you have a measurement to the bolt face.

 

[GenePoole]

OK, Alan, I've analysed your picture, and it looks sound, but I see no real difference in whether you pick the SAAMI datum line or your shoulder junction line as a given. They work out the same, but your method requires 3 trig operations. Maybe I missed a step.

 

[johnfred1965]

When I was in math class they always taught us the long hard way to figure things out, before they showed us the shortcuts. However in this case, JUST BUY A GO GAUGE!

 

[GenePoole]

That was kind-of the point. It's not trivial.