On sbr’s like 10.5" or 11.5" do the barrels wear out or burn out faster than a 16" or 20" barrel?
Depends on what your calling burn out.
If you wean throat erosion then yes.
Barrel no good after 4k rounds?
Right you are. You can also see gas port erosion faster.
C4
No. If it is CL’d, then you should get at least 20K (if fired on SA).
C4
why would erosion be faster on a short barrel?
- BACKGROUND: There have been continuing incidents of failure to extract/eject with the M4A1 Carbine. The most frequent failure is characterized by a stoppage with a spent case and a live round in the upper receiver between the bolt carrier assembly and the chamber. This stoppage is caused when the extractor loses control of the spent case as it is being pulled from the chamber, and is possibly exacerbated by incorrect bolt velocity. Other factors, such as increased rate of fire, weakened extractor springs, very hot chambers, and gas port erosion may contribute to this stoppage.
http://www.dtic.mil/ndia/2006smallarms/taylor.pdf
Page 48 is where the meat and potatos resides.