Debugging my misfires

[arbol]

I was hoping the other persons thread would help me too, but it didn't.

I have an AR-15 Pistol, that I built myself from Palmetto Armory components.

This is one of several rifles I have built.

This rifle, misfires. Often. Probably once per 30 rounds, and once it starts misfiring, it keeps misfiring (heat related?)

The symptom of the misfire, is that the spent round is not fully ejected, which causes the next round to get snagged up, etc.

Any guidance would be appreciated.

-John

[whitewalrus]

What cartridge? Barrel length?

Are you shooting brass or steel? What is the ammo you are shooting?

How is the previous case not being ejected? Is it fully stuck in the chamber? Stovepiped? Pictures of even video of this would help.


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[arbol]

PSA 10.5" 5.56 NATO 1/7 Phosphate 9" Lightweight M-Lok Freedom Upper - With BCG & CH

Barrel Length: 10.5"
Barrel Profile: A2
Barrel Steel: Chrome Moly Vanadium
Barrel Finish: Phosphate
Chrome Lining: No
Muzzle Thread: 1/2-28
Chamber: 5.56 NATO
Twist Rate: 1:7
Barrel Extension: M4
Diameter at Gas Block: .750
Gas Block Type: Low-profile
Muzzle Device: A2 Flash Hider
Receiver Material: Forged 7075 T6
Receiver Type: A3
Handguard Type: Lightweight M-Lok 9" Free Float Rail
Bolt Carrier Group Included: Yes
Bolt Steel: Carpenter 158
Bolt Carrier Profile: Full-auto
Charging Handle Included: Yes
Overall Length: 19.5"

Barrel: 10.5" Chrome Moly vanadium steel, phosphate coated and chambered in 5.56 NATO with a 1 in 7" twist rate. Pistol length gas barrel is finished off with a PSA 9" Lightweight M-Lok Rail, a low profile gas block and an A2 Flash hider.

Upper: Forged 7075-T6 A3 AR upper is made to MIL-SPECS and hard coat anodized black for durability. These uppers are made for us right here in the USA by a mil-spec manufacturer.

Bolt: Bolt is made of Mil-spec shot-peened Carpenter 158 steel. Gas key is secured with grade 8 fasteners and staked per mil-spec. Bolt carrier is parkerized outside, and chrome lined inside.

Plus a: high quality lower build kit with everything you need to assemble your AR-15 lower into a pistol. Features polished hammer and trigger contact points, and black oxide coated hammer and trigger springs. Also includes SB Tactical SOB Pistol Brace, double-looped pistol latch plate, carbine buffer spring, and standard carbine buffer.

My normal ammo is high quality brass, Federal.

Most of the time I see the new round trying to enter the chamber, but it is blocked by the old round not exiting the chamber correctly.

-John

[arbol]

I think many/most times it is stovepiped (fully stuck in the chamber.) It only becomes other than that as I try and resolve the misfire.

I'll take pictures/video next time I am at the range.

-John

[DenverGP]

I think many/most times it is stovepiped (fully stuck in the chamber.)

Stovepipe is when the empty case gets stuck in the bolt/ejection port after firing. If the case doesn't come out of the chamber, thats a whole different problem.

I had a new AR where the fired case wouldn't eject... Turned out there was a burr in the chamber, causing the brass to stick once it expanded. I used some fine steel wool on an AR chamber brush on a drill at low speed. Polished up the chamber, and never stuck another case after that.

The other option for a stuck case would be a failed/broken extractor, or bad/missing extractor spring/o-ring. Easy to try swapping the BCG from another AR that you know runs right.

[whitewalrus]

Is the old case stuck in the chamber or does it come out easy when you eject it?

Stove pipe would be it not stock in the chamber, think of the brass sticking out the ejection port but held to the front. See pictures here: https://www.wingtactical.com/how-to-...and-stoppages/


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[DenverGP]

I believe a slightly heavier buffer can also help with fail to extract, as it can delay the BCG moving backwards, giving the brass case a little longer to return to normal size after firing..

At least that was the theory I was told when I had the issue.

[arbol]

Thank you for the pictures. I get a bit flustered when this happens so I don't think I process the problem in a logical way, and your pictures and discussion will help me when I am next at the range.

I'll try and get out this weekend and give you all an update after that.

Thank you!

-John