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Discussion Starter · #1 ·
Recently a friend's AR hadn't been functioning properly. He gave it to me to see if I could figure out why. It's not worth getting into the full story on these guns, but he and I each bought one about 5 years ago. We got them for a great price from a local-ish company but they are a hodgepodge of random parts and were built as cheaply as possible. We figured all this out with a few trips to the range and our land in the mountains.

- Many FTF's
- Bolt would lock open with rounds still in the magazine

FTF problem:

- It was FILTHY. My buddy is not super keen on gun maintenance. A bore snake and more lube was the most this thing has seen in 5 years and probably around 1k rounds. During cleaning I found this, firing pin and firing pin retaining pin:

There's part of the problem. No idea how long it's been like that. The other part of the FTF problem was that after every few shots the hammer pin would walk, one end would slip down into the FCG pocket, which made the hammer crooked and it would either deflect off the carrier and still hit the firing pin or hit the bottom of the carrier and stop altogether. Solution:A new firing pin/retaining pin from my PSA field repair kit and a set of the $5 DPMS extended hammer/trigger pins with e-clip retainers (he didn't want to spring for $30 KNS pins, but these work fine).

Bolt locking open problem:

BCM upper we measured, assuming it is "right"

Buddy's upper:

Assuming the BCM upper is correct, the upper on the misbehaving rifle is 0.025" wider than it should be. So when the bolt was closed the BAD lever would hit the outside of the upper receiver and the bolt catch would barely clear the bottom of the bolt face.

Misbehaving rifle....note lack of clearance between bolt face and catch. Photo is taken while manually holding the charging handle back and pushing down on the bad lever.

BCM upper/PSA lower also equipped with BAD lever. Note much more clearance between bolt and catch.

Problem: bolt locks open with round still in magazine. Cause: combination of out of spec upper receiver and BAD lever creates too little clearance. Solution: remove BAD lever.

Nothing really earth shattering here but I had fun diagnosing and fixing his troubles and thought I'd share what we found and how we fixed it.

Premium Member
9,171 Posts
I never heard of the phase 5 lever but I googled it and it looks pretty nice. Not nice enough to replace my 3 magpul levers, but I do have 2 lowers with no plans that one could be good for...
Thats why it was invented. A one piece lever that will work regardless of the receiver size. BAD came out afterwards. i have seen many ARS with it lock the bolt back with ammo still in the mag. Many people switched to a Phase 5 or took the BAD off because of that reason. If the inside of the receiver is tight on the bolt or the pin lugs on the upper are offset to the right, it makes everything tight. There was a rash of uppers out there not too long ago that had that issue-and some were 'big name' companies too. Now you add material behind/inside the top of the bolt catch/release and the tolerances get tighter to the upper and the catch engages a little. Sometimes it wears in and the sporadic bolt lock issues goes away, sometimes it doesn't.
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