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10/20/2017 1:01:18 AM
9/22/2017 12:11:25 AM
Posted: 9/2/2005 8:34:27 AM EDT
An AR15.com member was kind enough to custom cut these for me. I had them made very similar to a USGI M16 Field gauge. These work very well.



Link Posted: 9/2/2005 8:40:19 AM EDT
I need clarification on this issue. Do .223 gauges measure to the same place on the chamber shoulder as the 5.56 does? If I understand it correctly, the chamber differences are in the throat, lead angle, etc. If I'm wrong, please direct me to the correct info. I may have it at home, and I'll try to dig it up. I had some damn drawings somewhere............................................
Link Posted: 9/2/2005 8:48:56 AM EDT
[Last Edit: 9/2/2005 8:50:02 AM EDT by AtlantaFireman]
I found the following here: Headspace, Torque values, and Barrel Break-in. It doesn't answer your question though.

"The Forster/SAAMI gauges available from Brownells are primarily intended for use with .223 Remington civilian rifles, but can be used with your AR15. The M16/AR15 series use their own peculiar specs for headspace, making it necessary to ignore the "Go' and "No-Go" markings, and look instead at the measurement marked on the gauge.

The current military specifications for the M16 series call for headspace of not less than 1.4646” and not more than 1.4706” on a new rifle. The commercial Forster/SAAMI gauges are marked in 1,000ths of an inch instead the 10,000ths of an inch that the dedicated M16 gauges are. When installing a new barrel, the commercial gauge measuring 1.465" can be used in place of the M16 "Go" gauge. Consider the 4/10,000ths of an inch difference an extra margin of safety. The commercial 1.470" gauge (the commercial "Field" gauge) can be used to confirm that the headspace is within spec for a new rifle. Unfortunately, there are no gauges available to measure between 1.470" and 1.4730", the latter being the measurement on the M16 "Field" gauge.

The M16 Field Service gauge measures a dimension of greater than 1.4730”. A rifle with a bolt that does not close on a Field Service gauge is considered safe to fire by the army, but not the Marines who use the military "No-Go" gauge for that measurement. Without using military Go or No-Go gauges, or commercial gauges marked with their measurements, you cannot know whether or not it is truly in spec. An interesting tidbit of information is that the Colt M16/AR15 Field gauge measures a dimension in excess of 1.4736”. It seems that the military has built in a bit more of a safety factor with their gauge."

I figured that this is close enough for me with quality parts.
Link Posted: 9/2/2005 9:39:17 AM EDT
Interesting. What did they end up running you, or would you rather keep the price quiet?
Link Posted: 9/2/2005 9:44:26 AM EDT
I traded another new set of GO and NOGO headspace gauges for his work.

I really think that there is a market for this in 5.56/223, .30-06, and .308. Why a manufacturer has not done this is beyond me.
Link Posted: 9/2/2005 9:52:06 AM EDT

Originally Posted By Stickman:
Interesting. What did they end up running you, or would you rather keep the price quiet?



Email/IM me.
Link Posted: 9/2/2005 9:59:01 AM EDT
So what would it take to get a set of those? I'd be in for a set, depending on price.
Link Posted: 9/2/2005 10:12:03 AM EDT
Link Posted: 9/2/2005 10:28:22 AM EDT
[Last Edit: 9/2/2005 10:31:35 AM EDT by AtlantaFireman]
I don't know what these would cost. A machinist member made these for me to see if it could be done. He emailed me from through my earlier post: I need a machinist to make rebated rim 5.56mm headspace gages: GO & NO GO.
Link Posted: 9/2/2005 10:41:30 AM EDT
Link Posted: 9/2/2005 11:35:53 AM EDT
That price was too good to pass up. I sold them to myself.
Link Posted: 9/2/2005 11:45:12 AM EDT
THOSE GUAGES SHOULD BE BANNED FROM CIVILIAN USE!

Especially during this natural disaster we're dealing with!
Link Posted: 9/2/2005 11:52:07 AM EDT

Originally Posted By blackta6:
So what would it take to get a set of those? I'd be in for a set, depending on price.



+1
Link Posted: 9/3/2005 6:19:47 AM EDT
I just wanted to point out that in the latest brownells catalogue (#58) while Forsters lists the same part number for 5.56 and .223, Clymer makes separate gauges.
Link Posted: 9/7/2005 11:37:28 PM EDT
WOW, there is a bunch of good stuff to talk about here...

First, I don't like the way those gauges are rebated all the way around.
You are slightly reducing the ability to measure across the whole bolt face like the cartridge case does.

Dave manson does a better job, he just grinds a simple slot on one side where the ejector will fit.
I have a surface grinder and I can do this modification for $5 per gauge if anyone else wants their gauges cut.

Next to Mongo's question:
> I need clarification on this issue. Do .223 gauges measure to the same place on the chamber shoulder as the 5.56 does? If I understand it correctly, the chamber differences are in the throat, lead angle, etc.

The 5.56 and the 223 both use the same datum line.
The datum line, for those not familiar, is a specific diameter on the shoulder.
In the case of 223/5.56, it is 0.330" on all the similar cases such as 221, 222 and 222mag.
What this means is that if you were to scribe a line on the gauge shoulder exactly where the shoulder is 0.330" in diameter and then measure to the end of the gauge, you SHOULD get the dimension marked on the gauge.
The major difference between 223 and 5.56 is in the field reject length and in throat dimensions.

Reference these:
Reamer dimensions: www.ar15barrels.com/data/223-556.pdf
Headspace gauge dimensions: www.ar15barrels.com/data/headspace.pdf

Randall Rausch
www.ar15barrels.com
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