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Posted: 10/5/2014 5:27:23 PM EDT
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Hi gang,
I just fired my Colt parts M16A1 semi auto build, which has a McKay 1/7" 20" barrel. The rifle buffer & rifle action/buffer spring came with the kit & are surplus. I used the M16 BCG for added weight. The brass is ejecting at about 4-4:30 position, but has a bur ? from the extractor? The bigger issue is the the brass is actually gouging the upper. Replace the action/buffer spring? Leave it alone? Thanks for the help. |
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Where is the burr on the brass? On the rim or on the neck? 4-4:30 is about optimum IMO or that's where most factory rifles and carbines throw it right out the box all brandy new. Usually burrs on the neck are from the barrel / chamber machining. Not uncommon even with top tier barrels. A little finesse can remedy in most instances. Rim distortion could be a variety of things but usually burrs are machining related. Ripped or distorted rims on cases are usually a function of gassing or chamber sizing. Ammo you are using would be good useful info. Pic of brass would probably also help. Take a dial caliber and measure total length of your spent case. This will tell you a whole lot about your McKay barrel chamber.
A lot of import ammo and even good ole USA quality ammo, many times isn't really in what I would call true spec. A lot of the M-193 sold for civillian use is sold simply to civillians because it didn't meet milspec whether it was powder batch ballistic related or dimension related. Seen more than my share of Federal LC ammo that was actually a little longer than mfg recommended 1.76 maximum length right out the box. Never seen any really short like FC stamped Federal. Not many people are gonna go to the trouble of pulling bullets and measuring brand new factory cases. Quality control at the civillian level might not be today what it once was in many mfg instances. Look at all the canted barrels slipping through the cracks. With ammo, in many instances one gets what they pay for and super deals might not really be such when one knows all the facts. A factory case that measures 1.768 will usually go bang and not blow up in one's face in most any AR .223 / 5.56 chamber but extraction could be a little rough. Seen a bunch of Privi and such that wasn't even close for other calibers not as much with .223 or 5.56. Point is it does make a difference at the expansion / contraction / extraction phase of the cycle as much or more than the initial bang. I've simply no experience with steel case except I've seen a lot of sweet builds that won't run worth a darn with it. Definately not gonna run it personally or take my time to disect any of it. As it's a quick flag for troubleshooting more than not. Brass hitting the upper is not uncommon. Look at most any used 603 or 604 surplus upper and 9 out of 10 will have plenty of ammo dings and these are true milspec weapons shooting true milspec ammo. There is a reason they started adding shell deflectors into the receiver forging and it wasn't totally for the left handed shooter. You can tune the extractor / ejector but what works for some doesn't work for others. There are some threads on different ways of tuning but I've never had a need. I simply put a piece of electrical tape over the shell deflector or on the side of my non shell deflector receiver when shooting so it doesn't scratch the receiver and down the road of many thousands of rds they still look like new when tape is removed. I usually only do this on the real nice collector pieces and beaters are already beaters. Can stop it but can't rectify what's already been done. Back to measuring cases. I don't like to see any of my cases exceeding 1.76in until I've fired them at least two and usually three times starting from a trimmed to 1.750 in. case. A normal case in an excellent chamber will usually stretch in increments such as 1.752-1.754 after first firing consistently with a batch. 2nd firing 1.756-1.758 . 3rd firing 1.758-1.761or2. At this point I trim back to 1.750 and when it reaches approximate 1.76 maximum or usually around 6 firings I simpy squash and recycle or load simply for plinking if case still appears sound and no cracks or obvious seperation. Most any used surplus barrel will exceed 1.76 with one firing and case will need a trim but on quality new mfg barrels USGI or civillian barrel if this is going on I'm selling it rather quickly unless it's money winner accurate and if so I'll expend the labor to trim the case after each firing. Otherwise it's too labor intensive for me to reload ammo for it. Kinda depends on what kinda shooting you're doing too. Plinking is simply that. Shooting for $10-100 per shot is a whole different ballgame and everything needs to be dead on. Bad enough to worry about atmospheric conditions and human error when making the shot much less crap ammo and even the best reloaders can turn out a batch of that from time to time. Good luck. Sometimes we over think a situation or remedy also. What's fun for some isn't for others. Main reason ice cream doesn't come in only one flavor. |
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Got a pic? Is the case still concentric when rotated in a dial caliper? If so I probably wouldn't worry too much about it personally. I just picked up some free brass that was way out on the case rim from one side to the other. Basically shot out of a questionable set up in my opinion. If so I'd lean toward chamber machining being a little tight but gassing can also cause the extractor to show a little abuse on case but not usually in rifle length stuff. Dissy or something similar SBR not really uncommon but rifle length is kinda tried and true. Did you headspace the barrel? Was headspace fine. Yes? Tight / loose? What's the McKay chamber 5.56 NATO? If headspace was great? Then a quick check for me would be to try another bolt I know works trouble free and try and narrow it down. You did clean everything very well before assembling? Not uncommon for new barrels to have a little debris in them. They need cleaning regardless of mfg.
If it does the same thing with another bolt you know functions fine in everthing else then it would point me in gassing / barrel / chamber direction and away from bolt. No experience with McKay barrels but pricetag alone kinda says lower tier any way you want to slice it. $200 is a lot of coins in one sense but not much when talking high quality barrels generally. Not to mention you aren't the first who has had problems with the McKay barrels and most were simply replaced by mfg. If other bolt is fine then I'd lean toward extractor / ejector spring on your surplus kit unit. Who did the FSB install? Did they clean it out? Some of that stuff was full of crud. I've used a bunch of the surplus BCG's with no problems but I do replace the rings and extractor spring / insert at time of build. Beats troubleshooting. Again good luck. There is always McKay customer service and barrel replacement if you can't remedy situation to satisfactory with little to no expense. I really like the IMI stamped ammo personally and LC M-193 is kinda the class of it all. |
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You can tune the ejector if it is ripping a gouge on the rim of your cases. It's just sharp extractor lips at work as usual. Reloaders usually are the one to notice this.
Another thing you can do to tame the system down in the ejection department is by taking off 1 or 2 coils from the ejector spring. If you're worried about jacking it up, you have another ejecotor spring in your pistol grip, driving the selector detent. If these operations are over your head, send your bolt to someone that knows how to do it and has the right tools. |
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