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New Member in need of AR-15 Guru.

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Unread 12-14-2009, 10:10 PM
Platinum Member
Join Date: Oct 2009
Location: Thunder Basin, WY
Posts: 1,788
Re: New Member in need of AR-15 Guru.

Originally Posted by NesikaChad View Post
A new gun with only 600 rounds through it shouldn't be having gas ring or gas tube issues. Not unless your going "Blackwater" on your dog fields. Sustained rate of fire on these is about 12-15 rounds/minute.

I'd start looking elsewhere. Ensure your cam pin isn't binding at all. This could delay coming out of battery on extraction and lead to a lethargic action/cycle.

Good luck.

The carrier did fall when using the "table top" method, not alot but it did move.
I changed out the gas rings anyway and the bolt feels quite a bit tighter now.

Ammo seems to cycle more reliably now, but bolt still won't lock back on empty mag unless I pull it back by hand.

Tube and key clearance mic's out at .005" (key is .180 and tube is .175)
I ordered another tube from Bushmaster anyway, don't know when it will show up though. Plan to replace it and try again.

I also ordered a JP Enterprises "low mass buffer" weighs about 1/2 of what my buffer is. I'll try the buffer and maybe even a new gas block from JP if the new tube doesn't do the trick.

Cam pin seems very free, but if it's binding up inside the receiver that will probably be a gunsmith fix I am assuming? Am also assuming that if it needs another bolt and/or carrier, that will be a smith issue too due to headspace issues?

Thanks again Chad
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Unread 12-14-2009, 10:18 PM
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Join Date: Oct 2009
Location: Thunder Basin, WY
Posts: 1,788
Re: New Member in need of AR-15 Guru.

Originally Posted by partisan1911 View Post
What brand of magazines are you using? It sounds like you are using GI spec metal magazines. The issues you are having sounds like your metal magazines have a crack which would expand a little when it is cold out. Depending on the amount of ammunition you put in the magazine will expand/retract the crack a little bit. I have had good luck with the HK magazines$$$ but have recently started using the P-mag. I have used the P-mag at -30F and 120F with no issues.

I have been using Colt 20 rnd and all sizes of Bushmasters stuff.

Haven't ever used any of the polymer stuff, if I can find one I'll give that a shot.
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Unread 12-14-2009, 10:47 PM
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Join Date: Jan 2007
Location: South Dakota
Posts: 753
Re: New Member in need of AR-15 Guru.

You may have an issue with the bolt going into battery with the lighter buffer.

The weights inside a buffer serve a very specific purpose.

Ever frame up a wall with a big nasty framing hammer? You whack away and give it that last good one to really seat the nail and what happens? The joint separates and you have hit it again.

The bolt will attempt to do the same thing. The spring will drive everything home and the bolt will rotate into battery, only to bounce back out and rotate the lugs out of battery.

The weights inside the buffer keep on whacking and keep the bolt locked up till everything settles down.

Just be forewarned in case the bolt doesn't want to stay put.

Chad Dixon
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Unread 12-31-2009, 02:14 PM
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Join Date: Oct 2009
Location: Thunder Basin, WY
Posts: 1,788
Re: New Member in need of AR-15 Guru.

Problem appears to be solved.

The new gas tube was .004" bigger, changed it out.
The tube was a little loose in the block, changed the block out.

Carl at ASI said that he uses a .1 port hole on his customs, so when I went through Denver last week I stopped by his shop and he opened the port to .103".

Went out last night (about 15 degrees and near zero with wind chill) fired 20 rounds single shot and let the rifle get good and cold again every few rounds. Bolt locked back every time. Has had about 80 rounds fired since cleaning. Last week, with only 60 rounds fired; Bolt wouldn't lock back on empty magazine.

It appears that the issue was a combination of things; rings wore out, tube ends too small, gas block too big and perhaps too small of a gas port. Whatever the case, all seems to be good now.........Yee HA!......HAPPY NEW YEAR!!
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