First AR 10 and ammo

ras_oscar · Apr 24, 2018

I am a recent owner of my first rifle on the AR platform, AR 10/308 manufactured by Anderson. After running through the first mag flawlessly, every 2nd or 3rd round on subsequent mag failed to fire and needed "persuasion" to retract the bolt to eject the unspent round (this receiver does NOT have a forward assist) I am running 150 gr FMJ manufactured by Fiocchi (because they had cases of it on the floor of the gun shop) I tried using several mags, including the first one that ran fine, so I believe it's either the ammo or the chamber needs breaking in. I cleaned the rifle when I returned home.

I am planning for my next trip to the range. I have purchased 1 box each of 3 additional manufacturers of ammo to see if that contributes to the issue. I have lightly oiled the bolt in contradiction to the manufacturer's recommendation that lube is not necessary (Hoppes). I also plan to bring a mop, cleaning rod, cleaning solution and and lube so I can clean out the chamber and or lube the bolt at the range if necessary to see if that makes a difference.

Is there anything else I can do to ease my next trip? I don't mind messing around with y rifle, jut not when there's people waiting.

DarrellA · Apr 24, 2018

I solved a similar problem with an adjustable gas block. YMMV.

2ndltsdad · Apr 24, 2018

might be a lube problem ?

erwos · Apr 24, 2018

This reminds me of when my dad's AR had a loose gas block. Might be something to poke at. Fiocchi should be quality ammo, so I'd be moderately surprised if that were the problem.

GuitarmanNick · Apr 24, 2018

I also vote for a loose gas block.

danb · Apr 24, 2018

Another vote for loose gas block. had this happen on an AR15. pretty easy to check.

iH8DemLibz · Apr 24, 2018

These threads continue to remind me of why I do not need an AR10.

danb · Apr 24, 2018

Loose gas block can happen on any AR, regardless of caliber. just depends on build quality.

ras_oscar · Apr 25, 2018

Talk to me like I'm stupid. How do I check for a loose gas block and if loose how do I tighten it up?

danb · Apr 25, 2018

The first thing I would do is get a flashlight and shine it through the handguard, and inspect the gas block. If you see residue bleeding from under the block into the barrel, its loose (or worse). You can probably get your finger in there to test it to see if its loose.

If I got my picture right, your gas block looks like this, below.

Supposing it is the gas block, you have to adjust it and tighten those two screws in the picture. You will need to take the handguard off. I would not do that tho until you are sure its the gas block.

d33rhunt3r · Apr 25, 2018

*Paging Mr Clandestine*

ras_oscar · Apr 25, 2018

So I simply need to ensure the 2 set screws are snug. Any harm in taking the set screws out (one at a time) and treating them with locktite to prevent loosening in the future?

danb · Apr 25, 2018

Make sure its aligned correctly over the gas port too. Loctite breaks down with heat, and it gets hot there. Rocksett or something for high temp.

danb · Apr 25, 2018

Also keep in mind before you mess with it, while loose gas block gets a lot of votes, it could also be something else related to the bolt, carrier/firing pin, or extractor.

lazarus · Apr 26, 2018

danb said:
Make sure its aligned correctly over the gas port too. Loctite breaks down with heat, and it gets hot there. Rocksett or something for high temp.

I usually use blue locktite on the set screws and haven’t had them back out. I can’t say for sure it is actually doing anything, but it doesn’t make anything worse. On my 10/22, which of course doesn’t get nearly so hot, red locktite (I didn’t bother with blue) was the only way to keep the receiver screws holding down the weaver rail from backing out. Still solid after a couple of years and a couple of thousand rounds. They’d back out after about 15-20 rounds before.

ras_oscar · Apr 27, 2018

danb said:
Make sure its aligned correctly over the gas port too. Loctite breaks down with heat, and it gets hot there. Rocksett or something for high temp.

What sets the alignment of the gas block over the port? Is it the length of the gas tube? The assembly videos I watched made no mention of how the 2 parts are aligned properly.

FWIW, I looked at the gas block as best I could without removing the hand guard. There is no sign of gas leakage around the port. The hand guard prevented me from checking the gas block set screws. I am trying not to mess with it too much, since it's a brand new weapon and the B&M has already volunteered to take a look at it if my second range trip also is problematic. I plan to lube the bolt carrtier assembly more liberally, change ammo and try again.

danb · Apr 27, 2018

ras_oscar said:
What sets the alignment of the gas block over the port? Is it the length of the gas tube? The assembly videos I watched made no mention of how the 2 parts are aligned properly.

FWIW, I looked at the gas block as best I could without removing the hand guard. There is no sign of gas leakage around the port. The hand guard prevented me from checking the gas block set screws. I am trying not to mess with it too much, since it's a brand new weapon and the B&M has already volunteered to take a look at it if my second range trip also is problematic. I plan to lube the bolt carrtier assembly more liberally, change ammo and try again.

If you see no leakage and its not loose, probably not the gas block. My next guess would be to check the bolt and carrier, make sure everything is tight, the firing pin retaining spring is not broken, etc. You might want to invest in some head space gauges just to satisfy yourself.

clandestine · Apr 27, 2018

Leakage around the gas block and/or gas tube is perfectly normal and is not an indicator of a problem.

I have read all of the post thus far and there is nothing that sticks out at me as to what I can advise to get your problem resolved without having to personally look at the gun.

You may need to either send this firearm back to the manufacturer for troubleshooting or take it to a well-respected armorer or gunsmith that specializes in the AR platform.

ras_oscar · May 14, 2018

Update: returned to the range this weekend, making the following adjustments:

1. Lubed he bolt carrier exterior , spreading the lube evenly on the entire surface.
2. Loaded each mag with 10 rounds instead of 25

After the first few shots, began getting double feeds. A range mate suggested I refrain from resting the rifle on the mag. After that it was big banging happiness for the next 180 rounds. Now I gotta dial in the new scope I just installed. Have also ordered a bipod to alleviate the magazine rest issue permanently.

Question: is there a resource that can assist me in determining where I should apply lube after completing a cleaning session?

Question: Will there be a time in the future when I will need to clean the interior of the gas system? I'm thinking it's going to get a lot dirtier than the bore, since the passages are so small.

clandestine · May 14, 2018

You don't have to clean the gas system. It's like a car exhause system but without emission controls.

If you are worried about obstructions you can use .080 weed eater line as a gauge and insert it into the gas tune from time to time to check for build up or obstructions

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