300 Blackout kaboom: squib or double charge?

[243winxb]

300 B.O. AR 15 pistol. Berry's 220 grain spire point over 9.5 grains of H110, COL of 2.20.

A special purpose loading like this, needs to use the exact components published in the data. NO substitutions with H110 or W296.

Note that Hodgdon does NOT list starting loads.

 

[bullseye308]

With H110 I believe they recommend it reducing by more than 3%. It has a very small range between works good and causes problems.

Glad to hear you only had minor injuries, definitely could have been worse.

 

[FROGO207]

It sure could have been worse, so glad it wasn't. I am thinking it was a double charge after hearing your story. Even a bullet setback would seem to not have caused as much damage. H110 is not something to light load either. FWIW I alwas try to load with something that will overflow the case when double charged if possible as a safety measure.

 

[mcb]

So the H110/W296 has generated a lot of weird reloader wives'-tails around it. Yes you're not suppose to download it too much but that is in reference to large volume magnum pistol cartridges and maybe cartridges like 450 Bushmaster and 458 SOCOM in most cases. 300 BO with a 220gr is not a high volume case, the bullet takes up ~40% of the usable case volume itself and there is not a lot of volume there to begin with. 300 BO has almost the same case volume as 357 Magnum but the bullet (for subsonic loads) typically takes up a lot more of it. H110 in sub-sonic 300 BO is already well below the pressure you see in the Magnum pistol cartridges its commonly used at. The OP's load of 9.5 gr of H110 under a 220 gr plated bullet is already above what it published for a 220gr bullet that Hodgdon does publish all-be-it a jacketed rather than plated bullet and it only generates 28 ksi, 300 BO is SAAMI rated to 55 ksi. I suspect the OP's .3 gr over published is offset buy the softer plated bullet requiring less pressure to engrave it into the rifles probably resulting is similar if not lower pressures than the published load depending on seating depth too Also H110 is a very popular powder for 410 shotgun loads many of which run down as low as 9ksi. So I said all the rambling to say as much as everyone seem to want to make a big deal of light loads with H110 I don't think that is relevant to this cartridge/situation.

 

[243winxb]

Also H110 is a very popular powder for 410 shotgun loads many of which run down as low as 9ksi.

Not free air space in the 410. Makes a difference.

 

[mcb]

Not free air space in the 410. Makes a difference.

Right it does make a difference, the point was the low pressure was not an issue especially if the case is reasonably full and there is very little air when you put 9.5gr of H110 in a 300 BO with a 220gr bullet. The powder occupies 60% of the usable case volume.