Need help 300 blk pistol issues

[horsemen61]

Ok guys I have had this lower for years couple years back I slapped a PSA 8.5 inch 300 blk upper on it ....... and I forgot about it for awhile now I’m trying to get it up and running


Here is the issue my buffer wants to puke out of it every time I take the upper off I even went and bought a Titanium buffer retaining pin first time I took it down it sent the spring flying found the pin though

So what is causing this?

Do they make a pistol length buffer spring?
It has the original sig brace on it

 

[Sour Kraut]

Can you provide pictures of the area where the buffer tube is held in place by the retaining pin?

 

[horsemen61]

I will when I can

 

[<*(((><]

Is your buffer retaining pin/nipple able to move freely? Your buffer tube should be screwed in enough to retain the pin from coming out but not touching the pin/nipple so it is able to move freely.

Another thought is maybe your buffer retainer pin spring is out of spec and not providing enough push, or it could need a drop of oil to help move freely.

Your buffer I guess could be out of spec and slightly too small of diameter allowing it to jump the pin.

Just some thoughts