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Posted: 11/23/2007 9:25:19 PM EDT
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I recently bough a barrel off of the EE when I was struck with the thought that it may have a .223 Remington chamber -- which would kinda suck, as I've been buying mostly M193 and the equivalent. 1. Is there an at-home method to check the chamber? If a bolt closes on Bushmaster's "GO" chamber gauge, am I good to go? 2. As the barrel is stainless steel (vs. chrome lined), is having the chamber re-cut an option? Thanks in advance, WhyTanFox |
Kinda. You can try to make a chamber cast (there should be a kit available at Brownells) but IMHO it's not for the faint of heart.
Not really, Bushmaster sells .223 gauges NOT 5.56 gauges. The only 5.56 gauges that I know are good are the military Field gauges Fulton Armory sells (and those just tell you if your chamber is too long).
Yes Last year in SWAT magazines Pat Rogers had an article on a couple of new AR tools. One of them was a 5.56 reamer that can be used by anyone to 'fix' a tight chamber. It wasn't cheap - but it seemed easy to use. (for information check the SWAT Magazine forum in the General area) WhyTanFox |
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.223 and 5.56 GO, NO GO, and FIELD gauges will be identical, for all practical purposes. There are very minor differences between gauges, depending the source (ie: Colt vs PPG). The difference between a .223 and 5.56 chamber is in the throat area, which does not have anything to do with headspace. The only way I know of telling the difference is to make a chamber cast. It is not very hard to do at all. The cerrosafe alloy melts at ~ 180 F, which is a relatively low temperature (below the boiling point of water). Block your bore right in front of the throat with a patch, pour in the metal, let it harden for 30 min, tip your barrel over and the cast should fall out. Wait 1 hour and measure the dimensions. Do not listen to those who say 5.56 is safe to fire in a .223. chamber. It is not. You will have excessive pressure. The question is whether or not you will see pressure signs on your brass. |
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Forest and organico, thanks for the great information. I did know that 5.56 was not safe in a .223 chamber (hence the question :-)), but did not know about chamber casting. If I decide to put anything in there besides my Ceiner kit, I'll be sure to cast and measure it first. Thanks again, WhyTanFox |
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Using a black marker, paint the bullet black and then chamber the round and eject it. If there are ANY marks on the bullet, close the point of maximum diameter on the ogive, do not fire the ammo in this rifle until you ream it out further. This means the bullet is touching the lands and that's not good as this is what increases pressure. If the bullet has absolutely no marks on it, it means the bullet is not touching the lands. |
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That will not tell whether the chamber is .223 or 5.56. In fact, I doubt it will tell the guy anything about his chamber, as the cartridge overall length is the same for the two rounds. A bullet in a properly loaded .223/5.56 round will not touch the rifling when chambered in either .223 or 5.56 chamber. A 5.56 chamber just has more room before the rifling begins. |
Are you quite sure of your facts? Are you absolutely sure that .223 FMJ is the exact same length at 5.56 FMJ? Have you measured it? |
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Get yourself a Stoney Point overall length gauge and a box of Sierra 77 grain MatchKings. Measure the overall length of the cartridge with the bullet seated to the lands in your barrel. (Your measurements may vary by up to 0.020" depending on the length of the particular bullet you use.) If your cartridge overall length is somewhere near 2.430", you probably have a 5.56mm NATO chamber. If your cartridge overall length is significantly less than 2.325" (that of a Krieger match chamber) odds are you have a 223 Remington chamber.    |
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That's very good Molon; you will also notice that the COAL you listed are much greater than magazine length. Also, that's your chambers you are measuring and we don't know how many rounds have been fired through your respective chambers. We all know that the leade grows with use. But it underlines my point very well. If your cartridges are magazine-length and they are touching the lands, you do not want to use them in that rifle. |
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