[Jim K]

Hi, CCholder. No, but it doesn't have to. The highest pressure is in the chamber and right in front of it, which is why barrels are made thicker in that area. In normal firing, as the powder burns and the bullet moves up the barrel, the pressure decreases. IIRC, the port pressure (an inch from the muzzle) in an M1 rifle is only about 2000 psi. If it were still 50,000 psi, the op rod would be very unhappy.

The same is true even more so without a bullet. Contrary to what is sometimes believed, few obstructions provide anywhere near the resistance of a normal bullet. Without that resistance and confinement, the powder burns poorly. The gas expands but acts like it is in a long cartridge case, so the pressure is a lot lower than in normal firing, and often the case is not even obturated, that is, the pressure is too low to expand the case neck to seal it and the case is heavily sooted. (In an excess of caution, I never use a full charge in shooting out an obstruction; 1/3 will usually do fine, with a cotton filler.)

Jim