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Posted: 8/28/2010 2:37:20 PM EDT
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By "this," I'm referring to the appearance of a couple of scoring marks at the top of my case necks.
Platform is AR-15, cartridge is .204 Ruger. Barrel is cut to SAAMI spec, which I believe features .100" freebore. These scoring marks are far too consistent to be the cases failing randomly. I'm getting two scores, one a bit longer than the other, the same distance apart, and virtually identical from case to case. I'm concerned because they seem to be causing the necks to crack prematurely. Here are some pictures: 
Thanks for any ideas. |
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So, this is happening as the round is chambered?
I'm still trying to picture exactly where you guys are talking about. Is it on the barrel extension, or the receiver itself? Can this be solved by removing the barrel and doing some polishing, or should I just live with it? Thanks. |
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Quoted:
So, this is happening as the round is chambered? I'm still trying to picture exactly where you guys are talking about. Is it on the barrel extension, or the receiver itself? Can this be solved by removing the barrel and doing some polishing, or should I just live with it? Thanks. it's happening as the case is being ejected. nothing you can do. |
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Quoted:
It's done on extraction, the case drags along the inside of the lugs of the barrel extension as soon as the case mouth clears the chamber. The extractor/ejector starts tipping the case towards the ejection port and the case hits the inside of the extension. OK, so I guess it's not a good idea to try to round the corners of those lugs just a little to stop this? |
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That's up to you and how comfortable you feel with modifying your rifle. A couple small swipes with a stone may be enough to break the sharp edge and prevent the scoring. Chamber an empty case and then extract it by hand slowly until it clears the chamber, you will see where it's hitting. Obviously don't get carried away... |
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Yeah, I did just what you suggested, and as you indicated, it was the lugs closest to the ejection port. I broke the rifle down (a process slowed by the failure of my Torx T10 driver and a quick trip to Sears), stoned the edges of the lugs with an Arkansas stone, then an India stone (or vice versa). It doesn't seem to be doing it any more, at least with manual extraction (which was enough to create the scores before). A trip to the range will hopefully confirm that I've solved the issue.
Thanks for the help. |
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Quoted: Yeah, I did just what you suggested, and as you indicated, it was the lugs closest to the ejection port. I broke the rifle down (a process slowed by the failure of my Torx T10 driver and a quick trip to Sears), stoned the edges of the lugs with an Arkansas stone, then an India stone (or vice versa). It doesn't seem to be doing it any more, at least with manual extraction (which was enough to create the scores before). A trip to the range will hopefully confirm that I've solved the issue. Thanks for the help. BT, DT. Also, reducing the ejector spring length just a tad will reduce the force which is engraving the case on the lugs. And since only reloaders will have issues with scratched necks, reducing the spring force will keep the brass in a closer pile to the rifle. |
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I've never disassembled a bolt to get to the ejector spring. So they make lighter springs, or do I just cut a coil or two off?
It also occurred to me after my last post, that i may not have polished the correct surface. I did the front corners of the lugs (the ones hardest to get to), but maybe it's the edges or even the rear corners that were causing the scoring. I guess I'll have to take another look tomorrow. |
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Quoted:
I've never disassembled a bolt to get to the ejector spring. So they make lighter springs, or do I just cut a coil or two off? It also occurred to me after my last post, that i may not have polished the correct surface. I did the front corners of the lugs (the ones hardest to get to), but maybe it's the edges or even the rear corners that were causing the scoring. I guess I'll have to take another look tomorrow. You're gonna have to experiment with that yourself. Go slow and I'd actually file, rather than cut, lengths off the spring. I hate to say it, but you'll probably kill a few springs finding your sweet spot. No matter how well you do, you'll end up buying a few more springs. I'd do that anyway actually. |
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Quoted: I've never disassembled a bolt to get to the ejector spring. So they make lighter springs, or do I just cut a coil or two off? It also occurred to me after my last post, that i may not have polished the correct surface. I did the front corners of the lugs (the ones hardest to get to), but maybe it's the edges or even the rear corners that were causing the scoring. I guess I'll have to take another look tomorrow. It should be the forward edges, so you may have gotten it. The rear corners won't contact an extracted case and score it like that. Like the guy above said, it usually goes away with shooting, but that's just the brass breaking the sharp edges over time, you're just speeding up the process... |
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Quoted: I've never disassembled a bolt to get to the ejector spring. So they make lighter springs, or do I just cut a coil or two off? It also occurred to me after my last post, that i may not have polished the correct surface. I did the front corners of the lugs (the ones hardest to get to), but maybe it's the edges or even the rear corners that were causing the scoring. I guess I'll have to take another look tomorrow. If you have a bolt disassembly tool, it is easy. If you don't have one but have a bench vise, you can make your own. Just cut the head off a .223 Rem case, about 1/4" is perfect. If you don't have copper or brass vise jaw cushions, cut another one to cushion the tail. Now put one case in the bolt, hooking the extractor and compressing the ejector spring, orienting the ejector pin. Carefully drive the roll pin out and then insert a SMALLER diameter pin into the hole. This can be a small nail etc, it is to capture the ejector. I trim the springs to barely leave some tension, this makes assembly easier as you do not need to compress it. And ejection is still positive. Clip the spring with diagonal cutters, squaring the spring on a grinding stone. Reassembly can be tricky, best to get the roll pin started, then slip the spring followed by the ejector. |
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1. the issue with scoring my case necks appears to be resolved. Thanks to all who assisted with this.
2. Keith: I made my own extractor compression tool, but when I compressed the extractor and tapped on the holding pin, it didn't budge. (I didn't tap very hard; I thought I'd check here first.) To my eyes, it looks like a 1/16" punch is the right size, but...is that hole in fact smaller than that? Also, I assume that I only need to compress the ejector a tiny, tiny little bit (just to take the pressure off the pin). Is this true? Thanks. |
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The pin should move without compressing the plunger. The only need for the tool is reassembly. And preventing the whole mess from flying apart. So be careful! I use an automatic center punch to get the pin to move. Get one at Harbor Freight and dress the tip to a very acute angle, just enough point to center on the roll pin. I made my own punch with music wire (hobby shop) and a length of 1/4" steel bar. The music wire is far tougher than a punch, round the corners so it won't damage the bolt as it is hard steel. |
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I've never found a bolt that i couldn't just push the pin out of with a punch or small nail by hand. Some would drop the pin with gravity if you just compressed the extractor with your finger a bit... ETA: Oh, you should be taking coils off of the EJECTOR spring, OP... |
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Well, I got mine out without damaging anything (or losing any parts!), but it definitely needed to be driven out. I guess Stag puts tight roll pins in their guns. The extractor pin, by contrast, did indeed push out with a minimum of coaxing.
It's all back together, and I'll cogitate on whether I should shorten the spring. Since my case necks aren't getting scored any more, this might not be that necessary. Thanks again to everyone for all the help. |
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Extractors pivot on the pin, ejectors are retained by a roll pin, press fit as the OD of roll pins are just a bit larger than the hole. The material is spring steel so it retains diametrical force. Extractors are meant for field disassembly, the extractor spring retains the pin as does the carrier's ID. |
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