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Short Cycling AR-15

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So I had a planned plinking session with a few friends and was excited when my new AR upper arrived just as I was about to leave. So, like an idiot, I just slap it on my lower and go. When I go to shoot it, charging it feels a bit gritty, but it shoots a few magazines of Federal XM885 like a champ.

Then I try some old (10 year+) assorted 55gr stuff I had lying around. It started short-cycling, usually the last 2-3 rounds of a mag. Changing mags didn't help and I had forgotten to bring some lube, so eventually I just fed it the 62gr.

Because I just moved and my guns have yet to move with me (complicated situation having to do with an gun-fearing landlord who insists on a gun safe or cabinet), this is driving me nuts thinking about. My first lower was fine running dry with the same 55gr, and it was a Del Ton (relatively cheap). This new one was a PSA (usually regarded as high quality) so I figured it would do the same. I seem to be wrong.

So my questions to all you more experienced guys are: Did I get a dud? Or are ARs just not good running dry and my first upper was a fluke? Or is my old crappy 55gr ammo to blame?
 
Could be a number of things, The gas block may be partially covering the gas port (my guess), gas port is to small. I have heard about a burr on the gas port inside from when they drill it causing problems. As long as the ammo was stored properly, and since you haven't had any trouble with another upper, it is probably good.

Hope this helps
 
OP
CFletch
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Thanks for the response Wally. After I get it back and clean/lube it, I'll check that. Know of any easy way to get to it? I don't have the tools to take the gas block off.
 
OP
CFletch
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Good idea. I thought it might have just been the lack of lube, but from what I'm hearing (and not just here) it should still have worked. I'll see what PSA says about it.
 
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Gas Impingement ARs like lots of lube. Give it a couple hundred rounds to break in before worrying about short cycling. Cleanliness is next to Godliness. Clean the bore and chamber and lightly lube them. Again, lots of lube on the bolt and bolt carrier.
 
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There are a few tricks to keeping AR's running during that break in period..

The first real magic trick I've found is Rem-Oil, it's pretty much all I use on my DI guns these days. It's a lightweight oil that includes teflon, so after a few hundred rounds it bakes in pretty good.

Second, if you want to know how "broken in" an AR is, take the upper off, leave the bolt carrier in (along with the charging handle) and slowly twist the upper so the bolt will roll out the back, if it starts moving at about 30 degrees from horizontal, it's good and broken in and won't give you any headaches. Until you reach that point, you need to keep up on cleaning and lubrication.

Also, despite the fact that del-ton is a "budget" upper, their stuff is top notch, I will admit some of their lowers are of medium quality, but their uppers are 100% they definitely are higher quality than DPMS/Bushmaster and IMHO, better than colt. When you're ordering the upper, make sure you spring for that chrome lined barrel/chamber, it's worth the extra $50 delton charges for it.
 
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Whenever you get a new toy, clean and degrease it thoroughly before taking it out for its maiden flight. While you are cleaning and degreasing, check for obvious signs of defects, such as burrs, etc. Once the gun is clean and degreased, then lube it up properly. In the case of your AR, that would mean a pretty generous amount of lube, especially on the bolt carrier. They like to be clean and wet.
 
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CFletch
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I can honestly say that upper works perfectly now! It just needed lube and some break-in.

Granted, I have a few hundred rounds through it since I started this thread. If ammo were available locally for less than obscene prices, I would shoot even more.
 
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Gas Impingement ARs like lots of lube. Give it a couple hundred rounds to break in before worrying about short cycling. Cleanliness is next to Godliness. Clean the bore and chamber and lightly lube them. Again, lots of lube on the bolt and bolt carrier.

if it's not dripping it's needs lube
 
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Let me add my 2 cents, the 62 grain functioned fine but the 55 grn caused short stroking, that's a big clue that lower pressure rounds could not overcome the friction of a dry bolt assy. It could also have been an out-of-plumb gas tube rubbing on the inside of the gas key. glad everything worked out
 
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I think I probably have 4k through my AR, the thing just runs, wet, dry, dirty, clean it doesn't matter, it just works. The limitation to this so far has been that fine moon dust that gets all over it out in the desert, this problem is compounded if I somehow, someway, for some reason (which always happens) drop my bolt carrier in the dirt. This is why unless I'm at the cabin, on a nice clean mat I won't break my gun in half.
 
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"Charging it feels a bit dirty". That was your clue. A new gun needs to be cleaned then lubed before firing the first time. Some have production or coating debris. Some need to be hand cycled after that. Meaning that you cycle the bolt inside the BCG. Did it hang up or gat smoother. Then cycle the BCG inside the upper receiver. You can sit in front of the TV to do this. When your happy go shoot it wet.
 
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Therein lies the problem! Currently cash strapped. Maybe with the tax return I'll be able to get the lower and a parts kit!
 

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