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Old 08-03-2010, 03:07 AM   #51
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Originally Posted by Jpyle View Post
Not to overcomplicate things or interject my apprentice level knowledge into the conversation but wouldn't a thorough inspection of the gas block, tube and key be one of the first steps?
It would, and that is great troubling shooting off the cuff. However, over the interwebz, I am going the route I am because the unit is/was:
  • brand spanking new with less than 150 rounds put through it & was assembled by a known manufacturer
  • in the hands of someone who isn't a gunsmith and this was their first build
  • functioning for the most part with 77 grain ammo ( one FTF )
  • and we have only tried one new magazine with the weapon.
There is nothing wrong with your assessment, and it might very well be that there is a partial blockage, but I kind of doubt it. With the pressure that builds up, if a few particles of packing material got into the tube, they would either be blown completely out, or blown into a position to completely clog the gas return.

I am not saying the gas tube or block is NOT the issue, but given the facts and the "over the interwebz without pictures" diagnosis - this is the best I have got...

JD
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Old 08-03-2010, 03:19 AM   #52
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Del-Ton packs it in a plastic bag, wrapped in paper. There are no packing materials of the type that could interfere here. And I can't stick anything from the upper end of the tube because I have no access to the barrel-end opening without taking things apart.

I definitely think I need to sit down at a range with my cleaning materials next to me, oil and such, as well as all of my mags and a few different kinds of ammo and just run through a protocol that could lead me to at least remove some possibilities.

Protocol possibilities:

-Clean, lube
-Fire one round from each of 3 mags, once charged with the charging handle and once again with the bolt catch. (is that clear?)
-Repeat process but with 2 rounds in each mag
-Repeat with 3 rounds in each mag
-Repeat above with each different ammo (start with hottest loads)
-At any point there is a FTF, keep round (for future photography and upload), open action for visual inspection
-Keep note if any particular combination causes the most difficulties.

Perhaps I should even purchase a couple of steel mags for this test. I'd sure like this problem to be something simple, especially a magazine, which is easily replaced.

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Old 08-03-2010, 03:43 AM   #53
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Originally Posted by Dillinger View Post
It would, and that is great troubling shooting off the cuff. However, over the interwebz, I am going the route I am because the unit is/was:
  • brand spanking new with less than 150 rounds put through it & was assembled by a known manufacturer
  • in the hands of someone who isn't a gunsmith and this was their first build
  • functioning for the most part with 77 grain ammo ( one FTF )
  • and we have only tried one new magazine with the weapon.
There is nothing wrong with your assessment, and it might very well be that there is a partial blockage, but I kind of doubt it. With the pressure that builds up, if a few particles of packing material got into the tube, they would either be blown completely out, or blown into a position to completely clog the gas return.

I am not saying the gas tube or block is NOT the issue, but given the facts and the "over the interwebz without pictures" diagnosis - this is the best I have got...

JD
JD, I agree 100%. Don't get me wrong, I am asking these questions as much for my own knowledge as anything else. I may be in a similar position someday with an upper that I have 1,000% percent confidence in but a lower that I built myself.
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Old 08-03-2010, 06:13 PM   #54
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Okay, I'm going to have to plan a session with all these tools.

Now, the extractor... I took apart the bolt to clean it. The spring in there has a green insert. When you say black insert, is color standardized? Like some mag manufacturers tout their green follower?

Would Keith's have extractor springs, buffer springs, etc?

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Old 08-03-2010, 06:52 PM   #55
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Originally Posted by CHLChris View Post
I definitely think I need to sit down at a range with my cleaning materials next to me, oil and such, as well as all of my mags and a few different kinds of ammo and just run through a protocol that could lead me to at least remove some possibilities.
Just go nice and slow with a note pad and camera. Take pics and write down questions as you go.

You have multiple mentions of oil. Remember, More is Not Better!

Quote:
Originally Posted by CHLChris View Post
Protocol possibilities:

-Clean, lube
-Fire one round from each of 3 mags, once charged with the charging handle and once again with the bolt catch. (is that clear?)
-Repeat process but with 2 rounds in each mag
-Repeat with 3 rounds in each mag
-Repeat above with each different ammo (start with hottest loads)
-At any point there is a FTF, keep round (for future photography and upload), open action for visual inspection
-Keep note if any particular combination causes the most difficulties.
+1 and a proceedure one should do with any new gun. Photo and write down ANY issues!

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Originally Posted by CHLChris View Post
Perhaps I should even purchase a couple of steel mags for this test. I'd sure like this problem to be something simple, especially a magazine, which is easily replaced.
I loath tupperware mags. I have had a scant few but 90%+ of my mag issues were with the plastic fantastics!

The first thing I would do is buy one metal mag, I like C-Products, and run the above test. I have both C-Products and Colt and have not had issue one with either.

I think tupperware has a place in the kitchen and MAYBE some firearm applications but NOT in such a critical process as feeding ammo! I know you guys see me as a "plastic hater" but my bias is not some personal conflict but based on my engineering background.
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Old 08-04-2010, 02:08 AM   #56
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plastic hater -

That's why I also recommended he get a metal mag to compare.

For the record - I have more P-Mags in use than any other in my AR's

But that doesn't mean they are for everyone, nor that they will work with no probs in anyone else's SUR's. They have been problem-free for me.

In answer to the insert - Chris, not sure if Keith's will have the inserts and springs or not. I know Bravo Co. and a few others do. Most of the carbines I've seen (complete) have come with either a blue or black insert. Most of the probs with extraction that I've heard of have been with the blue insert. Does that mean they're bad? No, not necessarily. Just that %-wise, it has been the case. Yours may not have the same issue. It was just another hint at things to check.

Midway USA has AR Stoner mags on sale right now, Brownell's has their mags on sale.

Check this link, too:

44mag.com

oh yeah...he's also local for us,

Another thing to try, clean your gun, some say soaking wet on the BCG, (that's a bit much), load up your mags again with the same ammo you used originally. See if you still have the same results. Then try a mag with the other ammo (more than 18 shots) and record your results. See if you can find some 62gr (SS109) or similar, and see what results you get.

Slo

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Old 08-04-2010, 04:25 AM   #57
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plastic hater -
He's like the uncle you gotta respect...cuz he'll thump you!

I just bought some stuff from Midway. They had a couple of great deals on some other stuff so I just bought some gear for this project:

2 C-Products 30-round steel magazines ($11 each)

Federal American Eagle Ammunition 5.56x45mm 55gr FMJBT, Box of 20
Wolf Gold Ammunition 5.56x45mm 55gr FMJ, Box of 20
Prvi Partizan Ammunition 223 Remington 62gr FMJ, Box of 20

DPMS Extractor Spring Assembly AR-15 (black rubber)

I also have those 2 types (BVAC and Hornady) of 77gr HP.

When they arrive I'm going to go for it. I read a great article on the exact process at work during the loading and firing of a round. AR15BARRELS.COM - Randall's description of AR gas operation and how everything works in harmony
It let me know that I really need to check each round's brass when they get ejected to look for indications of pressures that are TOO high (AND make sure they even ejected at all!). After reading the article, I don't think I should let any round go un-inspected.

I also think that at least a bit of this might be a break-in period with the buffer and action spring. I'll probably shoot those 5.56x45 rounds first and get some strong loads in there to break it in a bit before I get too hot and bothered.

I just better not find out that I got an upper from the Del-Ton factory that wasn't adjusted correctly.

I'll definitely make sure that lubrication is not the problem. But once it is all working properly, it should not require a huge amount of oil I would assume.
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Old 08-04-2010, 06:52 AM   #58
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Chris I hope you get to the bottom of this soon. I think Cane's right that it's unlikely a gas problem is causing the short stroking in a brand new upper but definitely make sure the carrier key is screwed down tight and staked.

Also I've forgotten are you using an H-buffer? You may have better luck with the carbine buffer with a midlength upper when firing weak ammo. I've tried both in my midlength and went with the H buffer because it was reliable with low powered Wolf so I figure it's the best choice in my rifle. The carbine buffer worked fine too but I've seen high speed videos where the H buffer greatly reduces carrier bounce in a middy. There's really no break in period with a buffer and spring, they should work fine from the first magazine fired.

Good luck!

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Old 08-04-2010, 07:00 AM   #59
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What's a carrier key? Are you talking about the tube thing at the top that goes around the gas tube?

This is a carbine, so I suppose it is possible I should look at the buffer, itself.

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Old 08-04-2010, 03:25 PM   #60
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See part two. That is commonly what is referred to when someone is talking about the carrier key. This is what harnesses the gas coming back from the gas tube and provides the motion for the bolt carrier group.

If this unit is not tight, is loose or is not aligned, then it is not harnessing 100% of the gas pressure coming back from the gas tube, and thus, you are not getting 100% pressure on the BCG to compress your buffer and spring.

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