I have been eying the 300 BLK for a while now. I think it meets its design requirements rather well. It has also impressively gained pretty wide acceptance rather quickly. I imagine this is due to the very serious marketing push it has gotten.
However, I’m not sure that it does anything that warrants me buying it.
In its supersonic loadings I don’t find it appealing because of its limited range vis a vis say 6.8 SPC II without offering any significant advantage inside 200 yards. If I needed more power inside of 200, it seems to me it would probably warrant getting out one of my 308s not the 300 BLK.
I think it is more interesting in subsonic loads. However, I find myself wondering if it is really a better choice for me to shoot subsonic than 9x19. I realize the BLK fires a rifle bullet with a higher sectional density and higher B.C. I understand that it should have better range than the 9mm. However, one I’m not sure that for me that slight advantage is very significant, and less sure that it offsets the advantages of the 9mm.
Moreover, I am yet to see a gel test (or even read a report) of a sub sonic BLK cartridge (and the whisper before it) with anything other than horrible terminal ballistics. Everyone I have seen has been a bullet poking a straight hole, no yawing, no expansion, no fragmentation. Even the soft nose bullets have shown no expansion. The heavy bullets used in subsonic loads simply were not designed with the very low velocities of a subsonic load in mind. A 147 grain 9x19 on the other hand will expand and seems to offer better subsonic terminal ballistics based on what I’ve seen. Of course new bullets could be designed to offer better terminal ballistics at subsonic velocities, but to the best of my knowledge, that has not happened yet. If and when it does, I may give the 300 a harder look.
If one is not shooting anything where terminal ballistics matter, but rather, one is just enjoying some subsonic range time, the 9x19 subsonics seem to be more economical.
In sum, I do not hate the 300 blk, I just don’t have a real use for it at this point. As a supersonic cartridge there are, for my purposes, better options. As a sub sonic cartridge I don’t see it’s limited advantages making it worth moving away from 9x19, particularly given the very poor terminal ballistics I’ve seen.