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Posted: 7/16/2010 3:20:40 AM EDT
| I understand (I think) heading spacing on the .223Rem rifle vs. 5.56 Nato rifle. What results will you get if you use a set of .223 head space gauges on a 5.56 Nato upper? Will they read correct for .223 ammo even if it is a Nato chamber? |
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no
>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. You should remove the extractor parts and the ejector, which normally requires four hands. Removing the ejector is a two-handed job if you have the proper tools, specifically a Sinclair Bolt Vice for the AR15. You can’t really reset the headspace on an AR15 with a chrome-lined chamber. That is set when the barrel extension is installed on the barrel. If you have an unlined barrel, with short headspace, a gunsmith can adjust it by cutting the chamber deeper with the appropriate chambering reamers. If the headspace is long, or the chamber chrome-lined, the only option is to try a different bolt until headspace checks good, or you run out of bolts. Then it is time for a new barrel. To recap, the specs are as follows: New Rifle Headspace: 1.4646" to 1.4706" SAMMI headspace gauges to use: 1.465" and 1.470" Unsafe Rifle Headspace: 1.4736" Use the Colt M16/AR15 Field Gauge: 1.4736" or, The US military gauge: 1.4730” Note: The Forster/SAAMI "No-Go" gauge measures 1.467" Sources for Gauges - Brownells: www.Brownells.com SAAMI gauges and a whole lot of new AR15 parts and accessories. Sarco: www.sarcoinc.com Military “Field” gauge as well as other maintenance items and M16/AR15 parts and accessories. The HEADSPACE GAGE is designed to protect your firearms from unnecessary damage and you, the shooter, from possible injury by showing whether or not the "headspace" of an action is within tolerance. Essentially, headspace is the distance between the face of the breech and the base of the cartridge when the action is closed. Accuracy and safety is threatened when there is excessive headspace. Forster Headspace Gages are made with painstaking care to insure you accurate testing of the chamber. Each caliber Gage comes in "GO", "NO GO", and "FIELD". If an action will not accept a "GO" Gage, it will not accept cartridge cases of maximum length. If it accepts a "NO GO" Gage the action may have excessive headspace. If the action accepts a "FIELD" Gage, it should not be fired. Every firearms owner should have Forster Headspace Gages for safety and accuracy. < |
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Midway has them for the .223 Wylde.
Go guage: http://www.midwayusa.com/viewproduct/?productnumber=859123&utm_source=froogle&utm_medium=free&utm_campaign=649 and no go guage at: http://www.midwayusa.com/viewproduct/?productnumber=366434&utm_source=froogle&utm_medium=free&utm_campaign=649 Don |
| This is the one I've been using for the last 4 years, AR Gauge |
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This is a copy paste I got from Clymer:
Sir, We set both go gauges at SAAMI minimum (1.4636”). We set our 223 Field gauge at SAAMI max. (1.4736”) (we don’t label a field gauge for 5.56 but use the 223 to be safe). No Go is were we have different grind lengths for 5.56 and 223. No Go 223 Rem = 1.4666” (match) No Go 5.56 Nato = 1.4696” We hear the mfr’s chamber their AR’s deeper than say a bolt action to get them to cycle better. Makes sense to me. Thank you for your interest and we look forward to hearing from you soon. Best regards, Todd Wilms Ph 248-853-5555 Fax 248-853-1530 1605 W. Hamlin Rd. Rochester Hills, MI 48309 www.clymertool.com [email protected] |
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