Too much powder?

[tonyjr]

I hand prime - after a few thousand , you can tell if something is different .
You might have a tight barrel = more pressure
Maybe crimped to much
I always check at least 2 manuals for powder - [ generally Lee and Hodgdon ] and if not the same - I go to another manual and always start at min load ,
All I use are jacketed pills and I check the hardiness of the copper [ drag pill head across a piece of steel - I use the square in and section of bench vice ]
If you care , all I use is hodgdon powders , CCI primers and jacketed pills .

[silvertriple]

General rule of thumb is to reduce listed max load by at least 10% and then work up. You got very lucky.

Smart move in pulling all the rounds.

[hambam105]

Doesn't the manual say....

Something akin to, 'Do Not Reduce Loads using H110 Powder' ? Reference Winchester 296 and .357 Loads. Maybe those rules don't apply to loads for 300 Black Out.

Has anyone mentioned loading a grain or two lower when using Military cases verse using thinner walled civilian cases?

[noylj]

One of the reasons I don't care for H110/296. You can't go very low and work up and you don't have any idea how your mix of components and COL will act until you've fired a round, usually quite close to the max load.
I much prefer 2400 for all the cartridges that either powder is good for as it is very stable and work well even in loads below the start load. May not give me that last 50fps, but has always been more accurate in my guns.

[bazineta]

The great thing about wanting to push a .30 bullet as fast as you possibly can is that there are so many cartridges available to do so, and for sure I'd look at one of them before deciding to start with a max load on 300 Blackout. A .308 might be just the thing for you.