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Thread: Chamber gauge
11-22-2009, 05:07 PM #1
What is the difference in length between a go and a no go gauge?
11-23-2009, 06:35 AM #2
11-23-2009, 08:14 AM #3
First, lets get on a common vocabulary.
A chamber gauge is quite different from a headspace gauge.
A chamber gauge is used when manufacturing ammunition at home. It's a tool used to simulate a cartridge being chambered in a firearm. It's purpose is to ensure the cartridge will physically fit in the gun.
Headspace gauges are used to verify the depth that a gun chamber is cut in a barrel. A GO gauge is typically made on the short side of that depth and a NO GO is made on the long side. The Sporting Arms Ammunition Manufacturer's Institute is the governing body that delegates what these dimensions are. In a typical rimless centerfire cartridge the distance from GO to NO/GO is .006". Rimmed cartridges and belted magnums tend to work a little differently, although a belted magnum cartridge can be headspaced off the shoulder/rim just like a rimless case also. This is popular with match/sniper type rifles as the datum point is more accurate this way. (Your not potentially blowing out the shoulder of the case when you fire it)
There is a better way to check this however.
Buy a GO gauge and obtain a strip of .001 steel shim stock. The stuff Starret makes works really well. Strip your bolt of anything that is actuated by a spring, and drop it back into the receiver. Now drop your GO gauge in the chamber. The bolt should close using the force of gravity.
Now cut a small postage stamp of shim stock and stick it to your bolt face using a dab of grease. If the bolt closes, repeat the process until it sticks. Your chamber is now actually measured. The distance being "GO plus .00 whatever the number of shims you had to use."
This is a valuable tool and one I encourage everyone to use because it allows you to monitor a few things. If you goof up and load a 30-378WBY magnum with H110 pistol powder and survive the experience your going to need to verify the rifle is still safe to shoot. One way to do this is to use this method. If you measured it this way the day you bought the gun and it's GO+.002" and now it's suddenly GO+.011" you know for certain that something yielded on either (or both) the receiver or the bolt.
If over a 10 year span of several thousand rounds your 223 or 308 changes you know the materials are being peened a bit and maybe it's time to consider a rebarrel and receiver tune up.
Last, it allows you to precisely set up your reloading dies so that you avoid overworking your brass during the resize operation.
Hope this helped.
11-23-2009, 11:12 AM #4
Just a bit of a quibble: For a bottle-neck rimless case such as 30-06, the "go" gauge is made to the SAMMI minimum chamber dimension.
The SAMMI maximum chamber length is typically .010" longer than the minimum chamber, but not always.
The "no-go" gauge is somewhere between the min. and max. chamber lengths. There is no SAMMI standard for the "no-go". Most gauge makers make it .006" longer than the min.
but they are no required to do so. In fact, adherence to SAMMI standards is voluntary.
11-23-2009, 04:48 PM #5
That is what I was looking for. If I do a chamber and it closes on the go gauge and won't close on the go gauge with a .005 shim on the back I should be in good shape. 223 is the chamber I'm interested in at this time.
11-24-2009, 03:29 AM #6
11-24-2009, 07:02 AM #7
It's a Remington 700 action no rapid fire. I just don't see the point is buying a no go gauge when you can get the same effect with a shim. In this case I cut the chamber to close on the go gauge and it won't close when I put a piece of .002" thick tape on the back of the gauge. I'm going to take it to the range today and see how it shoots.
11-24-2009, 07:30 AM #8
Your on the right track chief.
The N/GO gauge has its place no doubt, but I would personally only use one when I had a pile of guns to inspect. A good example is when I spent three years in Iraq working for the State Dept as a firearms technician. Performing and LTI (limited Technical Inspection) on over a 1000 Colt M-4's is pretty much like invasive testicle surgery minus the anesthesia.
Stick to the shim method as it allows you track any changes over time.
11-24-2009, 09:44 AM #9
edit: i don't buy no-go gauges and i buy my go gauges from ptg at the same time as i buy the reamer.
12-02-2009, 07:52 AM #10
Thanks for the info I went to the range and after a short barrel break in I put 5 shot in a .321" group at 100 yards. I did some action work, re cut the threads, lugs, and face along with the new Shilen barrel. For a reworked factory gun I'm pleased with the results.
12-02-2009, 08:29 AM #11
Just to quibble with you a bit Chad....Modern terminolgy the chamber gauge has become what you say...Headspace gauge is a modern term only put into use with the creation of Standardization in the early 1900's. Prior to that chamber gauge and head gauge meant the same thing. You will find the term interchangably used in older writings. I do, as I work with older chamberings.
The term chamber gauge was phased out and the term head gauge has been modified to headspace gauge during the 20th century.
THe method of measuring between the back of the head gauge and the breech or bolt face was how it was done pre standardization.
The original inspection instructions for my pet rifle the 577/450 Martini Henry state when the rifle is assembled a head gauge is inserted in the chamber and breech closed. The gap between the head gauge and breech face is measured and if it is less than .010 or less the rifle passes. This is for a arsenal new build.
12-02-2009, 10:48 AM #12
12-02-2009, 11:05 AM #13
That group was shot with the ejector removed. Which bring up a question who sells a weaker ejector spring? I know I could cut it off but I would rather replace it with something that doesn't throw the case 20 feet and ding the neck as it clears the chamber.
12-03-2009, 08:30 PM #14
If you think about it the firing pin should have absolutely no bearing on the head space gauge as it has a center in it plus, the firing pin should not be protruding out of the bolt face anyway. Also, the ejector shouldn't be holding the gauge off the bolt face but it would put a bit of side pressure on it, it never seemed to make much of a difference for what I was doing.
Say, don't you hang out on FNFAL.com? If so, I'd be Dave1 but don't hang there much anymore, too much bickering.
Last edited by SchneiderMachine; 12-03-2009 at 08:32 PM. Reason: addition
12-04-2009, 06:04 AM #15
Not me I have never heard of fnfal.com, but I will check it out. My reason for stripping the bolt it to get a better feel.