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Old April 30, 2013, 02:20 PM   #1
Garyson1311
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New AR build fail to feed 223 but not 5.56???

So I just got my first build completed and took her out to the range for the first firing. Before I get to what happened, heres whats under the hood:

New Frontier Armory LW15 lower
CMMG LPK
JD Machine Tech Upper
Palmetteo State Armory m-16 MPI BCG
Spkes LE 16" 5.56 barrel 1:8 twist
YHM Free float rail
YHM low pro gas block with DPMS gas tube
Cheapass pro mag 10 rnd from big 5 sporting goods (better mags en route)
BCM Gunfighter mod 4 charging handle

Okay and as far as ammo, I brought a box of 5.56 with a mil crimp (I believe it was some old lake city stuff) and I had a box of PMC bronze 223.

I thought I gave her a good lube job (using CLP) and decided to do a test firing with 1 round in the mag only as prescribed by some people here and on AR15.com(Thanks guys!), Anyhow, I loaded up one round of PMC 223 relased the BCG, it locked up tight, went bang, extracted, and locked the bcg back like it was supposed to. I was happy as a clam!

Then I loaded up 3 rounds and the first 2 went off without a hitch and the 3rd one just clicked. Upon further inspection I realized that the 3rd round was still in the mag for the most part but hadnt moved enough to hinder the bolt from closing either totally or for the most part. It looked like it (the bolt) was completely closed but if it wasnt, it was not open by much. ( It didnt look like it had stopped short when looking in from the dust cover). What pretty much happened was that I pulled the trigger on an empty chamber. At first I thought it was randomly short stroking the PMC 223 and the bolt just wasnt coming back enough to cycle but when doing a 1 round test, it fires and locks the bolt back which makes me wonder if it is the gas block or not (If im wrong, please correct me!) I tried this test 3 times with the 223 and it locked back every time. I proceeded to load the mag a few more times with 5 rounds of the PMC 223 and at least 1 of the 5 rounds had this same problem. For instance, i'd have 3 rounds go off no problem with proper feeding and ejecting and then on the 4th one, nothing but a dry fire which would require me to manually charge the weapon and upon doing so, it worked again. The malfunction didnt seem to be on a particular round in the mag, it did seem truly random since on some 5 round mag loads it would happen one time and on others it would happen twice. I then loaded the same mag with the 5.56 and had no issues at all. I loaded the same mag 3 times with 5.56 and it functioned beautifully. I just dont know whats happening because for the most part, the 223 functions well but every so often, it just doesnt feed and the bolt seems to close. There was a guy there with an AR15 who SAID he was a gunsmith and he lt me try one of his USGI mags with a magpul follower and I had the same problem. He said I should dril the gas port on the barrel and buy an adjustable gas block but I have no plans on doing that.

I did some searching on here and I saw that some people attribute this sort of thing to improper lubing, bad ammo, gas problem, or a break in issue. All of my parts are brand spankin new so I just wanted to see what you guys think this is given my particular situation. Im wondering if I should shoot it a little more and see if its a break in issue before I strip it back down and start messing with the gas port. Thanks! Oh and heres a pic!


Last edited by Brian Pfleuger; April 30, 2013 at 03:07 PM.
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Old April 30, 2013, 02:35 PM   #2
Quentin2
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Ok it happened with two mags... And two brands of .223 ammo? I didn't quite understand you there. But hotter 5.56 functioned fine...

Anyway, you're right definitely don't listen to the guy about drilling out the gas port, that's an absolute last resort! I'd run more ammo and different kinds, definitely some hotter stuff when your new mags arrive.

Since you installed the gas block, gas tube, etc. they are suspects. After a few magazines fired look for signs of fouling around the gas block which indicates a leak.


ETA:

What buffer weight and what gas length, carbine or midlength?
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Old April 30, 2013, 02:44 PM   #3
Garyson1311
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New AR build fail to feed 223 but not 5.56???

Hey thanks for the post. To clarify I was only using one mag with 2 different kinds of ammo and using that same mag the 556 worked great and the 223 worked somewhat. You mention gas issues but if I tried it with one round in the chamber and it fired and locked the bcg back, wouldn't that mean the gas is good? If in wrong please correct me as I'm an ar15 newb. Thanks.
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Old April 30, 2013, 02:45 PM   #4
Garyson1311
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New AR build fail to feed 223 but not 5.56???

Carbine buffer mid length gas.
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Old April 30, 2013, 02:49 PM   #5
Quentin2
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Quote:
... You mention gas issues but if I tried it with one round in the chamber and it fired and locked the bcg back, wouldn't that mean the gas is good? ...
I get the feeling you haven't put enough rounds through to make that call yet. How many rounds so far? I really think more rounds need to go down the pipe before you can be sure of all the symptoms.
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Old April 30, 2013, 02:52 PM   #6
Quentin2
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Quote:
Carbine buffer mid length gas.
Sounds good there, should be about right with the heavier M16 BCG.

And a standard buffer spring, not a heavy one?
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Old April 30, 2013, 02:57 PM   #7
Garyson1311
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New AR build fail to feed 223 but not 5.56???

Ya it's a standard spring. As far as round count, I didn't shoot it much, maybe 35 rounds.
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Old April 30, 2013, 03:02 PM   #8
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Can it be a break in thing? Maybe everything is really tight and I need to put some more rounds downrange?
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Old April 30, 2013, 03:02 PM   #9
Quentin2
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I'd put at least 100 more of 5.56 using your new mags then try again with the PMC. And of course look for gas fouling around the gas block. It's fairly common and often seals up by itself after use.

I kinda think this is going to work itself out with more use.
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Old April 30, 2013, 03:03 PM   #10
Quentin2
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Quote:
Can it be a break in thing? Maybe everything is really tight and I need to put some more rounds downrange?
Yeah, I think that'll do the trick.
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Old April 30, 2013, 03:17 PM   #11
Garyson1311
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Okay thanks for the responses, that makes me feel a little better. Hopefully its nothing more than a break in issue. I'll try and put some more 5.56 down the pipe, keep an eye on the gas block (im assuming if theres no leak it should be relatively clean and if its leaking there will be a considerable amount of junk around it?) and then i'll give the PMC 223 a whirl.
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Old April 30, 2013, 03:43 PM   #12
Quentin2
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There's a good chance you'll see carbon fouling around the gas block, it's common with a new build. You only worry if it's excessive and doesn't seal up after a few hundred rounds.
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Old April 30, 2013, 03:47 PM   #13
Garyson1311
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Okay, so it just sounds like I need to shoot the sucker some more and theres a chance that in doing so (using 5.56), it may loosen up a bit due to break in and start working properly with the 223 and if it doesnt, at that point I should try and diagnose problems?
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Old April 30, 2013, 03:55 PM   #14
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That's what I'd do!
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Old April 30, 2013, 03:56 PM   #15
Garyson1311
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That sounds like the best option. I will go ahead and try that. Thank you so much for your help.
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Old April 30, 2013, 04:15 PM   #16
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I hear about first time builds needing a break in period. It happened to mine, took about 80-100 rounds before there were no more extraction issues.

Maybe break down the buffer and BCG for a good clean and re-installation. Check if the gas length and buffer tube are the same.

BTW, she sure is pretty.
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Old April 30, 2013, 04:28 PM   #17
Garyson1311
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Thanks for the post. Yeah im at like 30 rounds total fired so knowing that yours took 80-100 rounds to work out the kinks makes me feel better. My issues are feeding issues as opposed to your extraction issues but either way, I think more rounds being shot is necessary.

Im planning on breaking it down tonight and giving it a good cleaning and one heck of a lube job. Gas tube length is midlength and buffer is carbine.

Thanks for sayin shes pretty! im really happy with how it came out!
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Old April 30, 2013, 05:04 PM   #18
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Yeah she does look good and I suspect a little more shooting is all she needs. You might speed things up by manually cycling the action/dry firing while watching an old Vietnam war movie!

Lots of lube on the bolt/carrier and contact rails of the upper receiver, too!
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Old April 30, 2013, 05:11 PM   #19
Garyson1311
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New AR build fail to feed 223 but not 5.56???

Definitely gonna keep her wet and work that action!

Thanks for the compliment, too!
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Old April 30, 2013, 05:24 PM   #20
Achilles11B
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Run different factory ammo (if you can find it) and different mags and see i anything changes. Just one guy's opinion.
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Old April 30, 2013, 05:32 PM   #21
Garyson1311
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That makes good sense, i'll definitely try that as well. Im gonna reload this PMC brass once its all shot up, maybe that'll change it too. Gonna load em with some nosler varmageddon 55gns I picked up.
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Old May 1, 2013, 12:58 PM   #22
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I run the BCG by hand until they'll close and lock by their own weight when released with the upper tilted muzzle down @45*. The first few shots should result in a fair amount of smoke as the lube burns out of the works.
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Old May 1, 2013, 04:19 PM   #23
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New AR build fail to feed 223 but not 5.56???

I had a gas block that was .060 off on alignment with the barrel port. Ended up machining it off and all functioned fine. I had the same issue as you.

I'm no AR expert but it seemed as though the block was intended for a free float grip instead of the style I had, the retainer that holds the grip in moved the gas block forward about what it was off. I'm guessing if I'd had a free floater it would have seated back tightly and been no issue
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Old May 1, 2013, 05:38 PM   #24
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Don't forget to post a follow-up. I'm in the middle of my first build and would like to hear what you find!
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Old May 1, 2013, 06:40 PM   #25
Garyson1311
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New AR build fail to feed 223 but not 5.56???

Mobuck mine definitely doesn't close in its own weight yet. I gave it a bath last night, lubed her up good and worked the action a hundred or so times this morning before work. I am also picking up another few boxes of 5.56 tonight that I am gonna take to the range this weekend. I am planning on getting it wet and putting about 100 rds of 5.56 through it, cleaning it, and then seeing if the 223 works. I hope it's just a lube or break in issue. Will definitely follow up!
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