Headspacing gauges

[OzarkExpedition]

Tuner or anyone else that has them. I was wondering if you could provide dimensions for these go and no-go gauges. Gonna do some tinkering at work on the lathe and would like to make my own. Thanks!

 

[1911Tuner]

Tinkerin'

Howdy! Ain't toolmakin' great?

Use any reloading manual to get your diameters and extractor groove dimensions. The GO length is .898 inch +/- .0005 The NO GO is .920 inch
also within a half thou. I made a .910 "Field gauge" to use for a yardstick
as to when the working headspace is approaching the time to rebarrel the gun, or just limit the use. Remember to cut a ramp in the rim that will allow the extractor to snap over easily, and let you push the slide to battery with the gauge in the chamber.

Note that some guns that are right on the edge will seem to go into battery on the NO GO. If you run into one that goes to battery with a little effort,
look at how the slide and frame align with and without the gauge. If the
slide "backs up" on the frame a couple thousandths...it's not quite in battery.

To check true working headspace on the GO gauge...use feeler gauges
between the rear of the gauge and the breechface from the underside of the slide. When you find a blade that will slip between with light resistance, add the thickness to the gauge length.

I also have a homemade .895 gauge for special applications.

Luck!

Tuner

 

[OzarkExpedition]

Mucho thanks. I really do appreciate it, and if I get time this weekend I will try and get them knocked out and post pics.

 

[Jim Watson]

Tuner,

You are using the term "field gauge" differently from what I have seen in such places as Hatcher, Wilson, and NRA. There it means a gauge longer than No-Go suitable for identifying guns needing overhaul. Unfortunately, they give no specs for .45 ACP Field, just the same Go and No-Go figures you do. Rifle Field is usually .003" or .004" over No-Go.

Confused the heck out of me until you gave numbers. If you want to check for .910" headspace, fine, but I don't think it is a real Field measurement as used by Ordnance or SAAMI.

By the way, in Hatcher, there are six headspace criteria for .30-06, from back when it was the service round.
New M1 minimum
New M1 maximum
New other rifle minimum
New other rifle maximum (same as for M1)
Overhauled rifle maximum
Field limit.

 

[1911Tuner]

Field

Jim said:

>Confused the heck out of me until you gave numbers. If you want to check for .910" headspace, fine, but I don't think it is a real Field measurement as used by Ordnance or SAAMI.<
**********************

Howdy Jim,
Exactly so. My homemade gauge isn't an ordnance field gauge...just a sort of quick-check gauge that I often surreptiously slip into a
pistol that I'm considering buying...or on my hard-use beaters to let me know when things are nearing the point of overhaul. That's the reason that I put
it in parenthesis. To wit:-----> "Field Gauge." It's a pretty good yardstick that lets me estimate the remaining service life of the gun...or whether I want to pay the asking price. Sneaky, what?

 

[OzarkExpedition]

diameter and extractor groove dimensions

Well, I dont reload and was hoping to get an easy google answer for that one. If anyone has a reloading manual and could provide those numbers as well I would appreciate it.

 

[1911Tuner]

Specs

Howdy Ozark,

The specs are in Kuhnhausen's shop manual #2 on page 105.

 

[Jim K]

Hi, guys,

Never let it be said that Tuner isn't on the ball. He whipped out those dimensions right to the third decimal place - and Ozark never even told him what caliber! BTW, it is also nice to have a diameter.

Jim

 

[OzarkExpedition]

Just noticed that... Darn, he is good! Let it be known, 45 ACP is what I was referring too. If I had some of that juiced up coffee that I have read they serve over in the Carolina's maybe I would have remembered that little tid bit!

Thanks Jim.

 

[Jim Watson]

Correct me if I'm wrong, Tuner, but shouldn't most dimensions of a headspace gauge except the length and front edge diameter be some smaller than a cartridge?
You do not want anything touching except the breechface and the chamber end.
Best to strip the slide, at least that is what they recommend doing with a bolt action rifle. And Clymer puts in clearance cuts in case you try to sneak one into an assembled gun. My FLG's .45 gauge has a notch in the rim, for example.

 

[1911Tuner]

*sigh*

Jim K! Ya mean we ain't talkin' about .45 ACP?

Okay! Okay! If I gotta do all the work...

Rim diameter....470 inch give or take .003 (This is for the gauge...not the cartridge.)

Body diameter. .470 inch + .001 minus zip. (Jim W...You don't want it
to be too far undersized so you can detect chamber taper as well as depth)
Just remember to break the front edge after facing it to length to prevent
marring the chamber...lightly...with a stone, as it spins in the lathe chuck.

Rim thickness...Set it to .045 inch...plus/minus .003 should do nicely.

Distance from the front side of the rim to the beginning of the straight wall in front of the extractor groove....130 inch plus/minus .003, but not critical if
you plan on removing the extractor. If you make a "Field" gauge for quick-checks, make sure that the extractor doesn't make contact with the taper.

Diameter of extractor groove....400 inch plus/minus .005 or so...but not critical as long as it's deep enough to prevent the extractor hook from bottoming out. Unimportant if the extractor is removed for the check.

Extractor groove angle...26 degrees, but not critical if the extractor is to be removed. Length from major to minor diameter... .080 inch plus/minus .003,
but not critical.

Minor diameter inside the groove should also be about .050 inch from front edge of the rim to the beginning of the taper...but it's not critical if the extractor is removed. The .910 gauge can be a bit sloppy at the rear for extractor clearance...and you can set the length at whatever you're willing to accept as a maximum headspace. I settled on .910 inch...but you may want more or less. I suggest no more than .912 inch.

If you don't plan on removing the extractor for the check, be sure to cut an
"Access" ramp in the rim for the extractor to slip over. Width unimportant
as long as it's wider than the hook. Angle not critical as long as it cams the extractor open smoothly and easily. I suggest keeping it close to the angle on the front of the hook.

These dimensions may not agree perfectly with a set of commercial gauges,
but they'll give you a workable set. Check the drawing in Shop manual #2
for reference. Sneak up on the diameters with a smooth mill file while the
lathe turns...Break sharp edges with a medium stone and polish with emery cloth.

Best I can do this early...

 

[mister2]

Tuner said:

My homemade gauge isn't an ordnance field gauge...just a sort of quick-check gauge that I often surreptiously slip into ....

Whew! I had to read that twice. Thanks for the clarification, Tuner. Good to see you back!

MR2

 

[1911Tuner]

Whew, Mr2

ROFL! Behave yo bad self!

Hope the preceeding text was understandable...albeit overlong and drawn out.
Kuhnhausen Volume II, page 105. A picture is worth a thousand words and all that rot...

 

[OzarkExpedition]

Tuner, I did it!

I wanted to post this really quick as the work day is over, but the Dad day isnt half over yet!

I managed to use the lathe at work for a while and turned out two really nice headspace gauges. The one thing that I wasnt able to do was the relief cut in the housing. Gonna have to borrow and end mill and set that up next week.

I wanted to say a big thanks for all the help I got here in making these. I will post pictures later today or tomorrow when I get a chance.

Thanks all for the great info!

 

[Sunray]

Headspace guages are cartridge specific and they should be heat treated. Which one?

 

[Jim K]

Headspace gauges are not always cartridge specific. For example, the .308 and .243 use the same gauge. All commercial gauges are hardened for durability since no one wants them to wear quickly or pick up a lot of crud in use. But for home-made gauges to be used only a few times, like Ozark is talking about, they don't need to be hardened.

Jim