Originally Posted by
Larry Gibson
With a bullet stuck in the throat, leade, etc. an AR bolt/carrier when drawn to the rear and released has sufficient momentum to push the next feeding bullet back into the case. I saw this many times over the years even with M193 and M855 ammo. It is particularly noticeable in FTE (failure to extract) where the fired case stays in the chamber, the action functions and the bullet of the feeding round is stopped by the case in the chamber. That bullet invariably gets pushed back into the case. In those instances the round will not chamber of course.
However, in the OPs case the soft jacketed bullet stuck in the leade was probably push a bit further into the bore while the bullet in the feeding cartridge was shoved back into the case. That in essence created a "110 gr bullet" (the combined weight of the 2 bullets) over 24 gr H335......obviously not good!
BTW; 24 gr H335 under a 55 gr bullet is a medium range 223 Rem load. It takes 25 - 25.5 gr to make the SAAMI MAP. It takes 26.5 to 27 gr to equal the 5.56 MAP. My standard load since the mid '70s has been 26.5 gr H335 in LC cases with a WSR or CCI 450 primer under a 55 gr Hornady SX (12 and 14" twist barrels). The measured psi (Oehler M43) in a 223 Rem chamber runs right at 59,500 to 60,000 psi.
Note; the psi I give are transducer/gauge psi's. The previous post psi's are CUPs. I'll also add that M193 made since around 2003 or 4 has the same measured psi as M855; 60 to 62,000 + psi. The older M193 ran around 58,000 psi which is about 4,000 +/- psi more than most 223 Rem factory cartridges are loaded to.