Foundation of Minds Charter School’s insignia.

We'll need a note to understand what this is. In truth, we'd more likely see a description of the insignia, followed by a note that this resembles the Foundation of Minds Charter School insignia, which is (description of school).

Any ammunition bigger than a traditional musket ball causes the bullet chamber to grow. SCP-XXXX is able to fire an hour's worth of any ammunition that is put inside of the bullet chamber. Excluding any Rocket Propelled Grenades (RPGs).

First, grow how large? Does it maintain the larger size after expenditure of the ammo? How much is "an hour's worth" of ammo? Why can't we use RPGs? I'm guessing ICBMs are okay, though? Can we load non-ballistic ammunition? Animals? Office equipment? If I load it with a gold bullet, do I get "an hour's worth" of gold bullets back out?

Basically, this area needs a deep revamp. It doesn't describe what's going on well enough and leaves too many holes.

members of the group called The Founding Family were found dead

Who?

those members that were dead were found with SCP-XXXX in hand.

A whole bunch of people were simultaneously carrying one blunderbuss?

there was a spent shell from an experiment done the previous day in their room

Blunderbuss ammunition doesn't normally have a shell casing.

Now any spent ammunition will now be considered SCP-XXXX-01, any more information will be given out after a few trials in order to assess the anomalous effects of the spent ammunition.

Whoa! You just said that any expended ammunition has no anomalous characteristics. This is contradictory.