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Posted: 3/31/2006 4:44:35 PM EDT
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I have a 14.5" chrome lined barrel that I purchased new about a year ago. The barrel shoots XM193 type ammo without problems. I recently ran into trouble with this barrel/upper when I started reloading. I'm experiencing difficult extraction and an occasional difficult chambering of full length resized rounds. Let's assume that my reloads are done properly, are to spec., and are just barely larger than mil-spec ammo, as is common with typical .223 dies. My chrome chamber has slight machining/turning grooves in it. Are typical chambers usually without turning grooves and "almost" in a polished state, even without polishing? Is this normal of a chrome lined chamber? Wouldn't the chrome tend to fill minute grooves, and also end up as a very shiny/polished type finish? My chamber finish is matte, almost as if it was turned or poorly reamed after chroming? Or am I totally off-base. . . and typically, only the bore is chromed, and the chamber is not? Thanks. M.L. |
I have the same problem with my BM barrel. I even went to a "small base" sizing die which is supposed to size it a little tighter at the base. Still no go. Everything goes through a chamger gauge just fine. My solution has been to shoot Wolf ammo and not worry about reloading for .223. |
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| Hard chrome as a plating can be mirror finish, or matt, or bead blasted. But in an AR barrel, in my experience, its going to look something like pencil led only a shade lighter, kinda like tin foil when no light is shinning on it (the non-shiny kind). PS. I asked the question earlier and Armalite at least chrome lines the inside of the carrier and key (as well as their barrels and chambers, as does bushmaster). |
5.56 chambers typically only differ from SAAMI spec by a couple of thousands of an inch, except in the throat-length department. The actual part of the chamber that houses the cartridge is essentially the same as .223 dimension, as far as I know. I have researched this extensively. If you have milspec drawings showing 5.56 cartridge and chamber specifications/dimensions/tolerances, please send them to me. I'll provide what I have regarding SAAMI specs and basic 5.56 dimensions below. Off-the-shelf reamer nominal dimensions, 5.56 vs. .223 I'm sorry, I cannot credit this source offhand. I think this is on the Clymer website. SAAMI .223 Dimensions with comparison of Dies vs. SAAMI Spec Dimensions |
And based on your own link above, how are you figuring that typical .223 dies are producing reloads that are "barely larger than mil-spec"???? |
Mil-spec 5.56 ammo is generally sized near the smallest end of SAAMI specs in order to assure consistent feeding in Full-auto fire, yet the 5.56 chamber is usually reamed slightly larger than 223 SAAMI chambers. i.e. 5.56 mil-spec ammo is manufactured slightly smaller than commercial 223 SAAMI spec ammo. 5.56 mil-spec chamber is slightly larger than 223 SAAMI spec chambers. Please set me straight on this issue. I'd love to see some mil-spec 5.56 ammo/chamber drawings with tolerance ranges. Edit: See the personal measurements that were done, summarized on the bottom of the second link. |
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props, I do not mean to offend you, but I have far graduated beyond understanding what "bumping the shoulder back" means. Even if i set sizing dies down to their mazimum amount (to where I'm having to force my press to cam-over), I'm still ending up with sticky cartridges in my chamber. I've evern measured these to make sure that my headspace is smaller than the chamber. Are you saying that small-baee dies are not needed for ALL AR-15s? M.L. |
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OK. I think that I am goig to give this up, and concede that my chamber is "sticky". Several visible machining grooves tell me so. Although it will work "as advertised". I don't think this is the upper that I should use for reloading. Actually, everyone here has just now justified my new purchase of a match chamber from Denny's Guns (the Stainless Steel "Recon barrel with M4 ramps and Wylde Chamber by WOA) Thanks, Now I just have to justify spending to my wife. |
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I've been loading since 1956 and have loaded for quite a number of AR's since I got my first one in the early seventies. I have NEVER needed small base dies on any of them. One thing that you might check is to see if the shoulder area of your chamber is clean and free of debris. Cheers, Phil |
What did you use to measure this? You mentioned you have a Stoney Point, correct? If you used the SP, what are the following three measurements: 1. Headspace of a fired cases? 2. Headspace of a re-sized case? 3. Headspace of the XM193 that works fine? A chamber gauge is simply not accurate enough to measure these differences. How far do you feel is required to bump the shoulder for a AR, to ensure 100 function? Don't take this personally, we are just trying to help. In most cases when this comes up, it is ultimately determined to be loader error, not that of the mfg. If any production ammo works, it is typically a loading problem. I have seen several dies that are just a tad long in the body, therefore not allowing the case far enough up into the die to move the shoulder far enough. The die, in that case, just need a tad ground off the bottom. BTW - I am in NW Houston also. You should join us out at ASC for our next match - end of April. There are about 10 of us getting together on a regular basis, and would love to have even more join. Just watch in the Texas forum as we always start a thread the week before. |
Roger on THAT! If you reload 5.56mm ammo where the empties were fired in an AR15, you have to TRIM CASE MOUTHS after resizing and before anything else. If you're going to use them for mutiple reloads, I find that after the first trim, I can get away w/every other time on trimming. If you haven't trimmed those cases, you've just ID'd your problem  Re the chroming, the only piece I've ever seen w/a bore that was chromed before the chamber was cut, is a Chinese SKS at my house. Every American chromed bore , as far as I have ever seen or heard of, had a chromed chamber as well. 
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| Even with small base dies you MAY have an out of spec shell holder. It may not be letting the die size the case down far enough. The common fix for this would be to either try a different shell holder or take a SMALL amount off of the top of the shell holder OR the bottom of the die. Try a different shell holder first as it's cheap to replace. YMMV |
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