Rifle buffer spring issues

[Takoda]

I have an aero rifle length buffer system the bolt will not lock back correctly. If I take out the rifle spring and install a carbine spring it will lock with no issues. I don’t have another .308 carbine buffer spring so I used a ar15 just to see. Any input on what is going on. 

[shooterrex]

You only need to list your problem one place.

How long is your buffer?

Pictures of what you are working with would help.

Real hard to help you without seeing what you have to deal with.

[Takoda]

37 minutes ago, shooterrex said:

You only need to list your problem one place.

How long is your buffer?

Pictures of what you are working with would help.

Real hard to help you without seeing what you have to deal with.

5 1/2 rifle length 

[shooterrex]

A 308 rifle buffer is 5.2"

Not 5.5". that is your problem.

[98Z5V]

^^^  He's right.  .308AR rifle buffers are 5.200" long.  AR15 rifle buffers are 5.900" long.  There are no uses for rifle buffers that are 5.500" long, unless that some custom stuff that someone dreamed up. 

Make sure your rifle receiver extension is 9 11/16" deep, internally.