My comments here would be the following, randomly presented:
1. I don't recall ever seeing a primer pop in a 5.56 chamber. Now this is based only on examining guns that DID pop primers, and of those, all were found to have "not 5.56" chambers.
2. Although my lifelong study is not yet over and is based on what different guns do or seem to do, as opposed to actual laboratory research, .223 Wylde seems to me to be OK with 5.56 ammo. Logic tells me it ought to be but I leaned a long time ago that actual result trump the most logical predictions (when Dad torched a drive shaft off a truck I was shocked that it was tubular and not solid. 8-YO-Me: Dad, you guys got gypped on that drive shaft! Dad: They're all that way.)
3. Many don't agree that .223W is good with 5.56. If that has been their experience I can't say they are wrong. I hear that from time to time but I don't recall every experiencing it.
4. As to what chamber a barrel really, truly has, the one and only best way is to make a cast. What is stamped on it seems "chiseled right there into barrel steel, must be true" but it's really written in Crayon on flash paper (I mean, depending on the source).
5. Going back to 4., if well over half the guns I examine in class have "not 5.56" chambers when they are stamped or engraved 5.56, I conclude that barrels marked ".223 Wylde" may not have that actual chamber. So I hesitate to judge a barrel too harshly unless I can confirm the chamber config.
6. .223 W barrels popping primers might indeed have some other issue or issues. My opinions of the options there:
6a: Overgassed. I feel safe in saying overgassed, undergassed, or even no gas port at all, does not contribute to popped primers. Whatever is popping the primers has happened and is long over by the time
the bullet reaches the gas port. Overgassed would relieve pressure from the barrel more, it anything.
6b: Nobody said this but I often hear it: "they are being cheap with the reamers and are resharpening them, that makes them undersized, that makes the chamber tight, that pops primers." I don't work in a
barrel factory but I know toolmaking and trigonometry and have consulted two reamer makers on this: no one uses a resharpened reamer because to resharpen it you would have to move everything so far
back that it would not be practical or economical.
6c: Short / long headspace, I will agree that could maybe have some effect on pressure but shockingly with all the other stuff that gunmakers and barrel makers get wrong, I very, very seldom see headspace
issues.
6d: If chambers can be off by tens of thousandths of an inch on the lengths, who's to say the land and/or groove diameter can't be maybe .001 too tight? Haven't heard of it, but it could happen.
When we are working with a total .006 interference fit between the bullet (.224") and the barrel bore diameter (.218ish), .001 on the land /groove diameters is a significant percentage. This would
be pretty hard to detect.
7. Everything has a tolerance. Even a perfect chamber can be on the large or small end of its tolerance. My opinion is that a true 5.56 chambers is not going to pop primers even if it's at the low limit for
diameters and lengths.
8. Back to chamber casts. Major pain in the ass, very technique intensive and time consuming, but it is the ultimate. Examining a chamber with a bore scope works pretty well as a field expedient, if
you have a borescope, of course. I've been enjoying the use of a Lyman Digital BoreCam for several years now and it's not the be all, end-all optically, and you can't measure diameters with it but it's pretty
easy to "read" freebore length. I "taught" my BoreCam to "measure" lengths. I laid the lens next to a machinist's scale, and on the display screen I Sharpied tic marks coinciding with every .010".
This makes a crude optical comparitor and it's not up to National Bureau of Standards spec maybe but you can easily tell a .223 Rem from anything else. Also you can just sort of compare lengths to
groove widths--a standard that seems pretty universally adhered to-- which, I hesitate to go from memory but I think it's .073. So you can look at that width and kinda compare it to some lengths.
BoreCams and very reasonably priced, I just got the new one that uses your phone for a screen, have not had time yet to fire it up.
9: I'm with everyone here in the quest for .5MOA groups. I'm not up to the level of many of you in many of the aspects of this quest but I gotta say that I have had very satisfactory groups with a true 5.56
chamber. I have zero barrels with .223 Remington chambers; in my range experiences I can't say I've seen a world of dif between .223W and 5.56. I have not ever personally popped a primer in a .223W
chamber. I'll grantcha that among National Champs at Camp Perry there are zero 5.56 chambers in use.
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Originally Posted by markm
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