I just found out the reason why it wasn’t working. I really feel stupid for spending money in buying a new bolt catch. I was about to go to the store to buy a new buffer tube and spring. Have my car key and wallet in hand, heading out to the garage.

Then…… I told myself why dont I measure the INSIDE of the buffer tube to see the inside depth of the 2 tubes. The problematic tube was about 3/4 inch shorter. Hhhmmm

I pulled out the collapsible stock and noticed a small pinhole. I inserted a small allen wrench and felt something moved. I started gently slamming the lower/tube and saw something sliding out.

What did come out? A stack of quarters, rolled in a black electric tape (10
Quarters). I can’t figure out who put them in there, when or how.

Mystery solved. It is working now. Lesson learned.

Sounds like that tube was used for a 9mm
AR.

Someone might have used a .308 carbine buffer in a 5.56 rifle. I'm not sure if the difference in a 5.56 and .308 buffer is ten quarters or not.

A carbine buffer is about 3.25", a dedicated PCC buffer is 4"

Before those came out people used a carbine buffer with a spacer (quarters)
A Vltor A5 buffer is the correct length and the A5H4 could be used as PCC's like a heavy buffer.
That's what I used in mine with a rifle spring.
Vltor makes dedicated SS PCC buffers now up to 10oz.

Were there enough quarters to pay for the new bolt catch? Even if there weren't, at least you came close to breaking even. LOL