What 2 Piper said.
I would add that there are those who feel that 7625 if kept toward the light side can ignite late, partly down the barrel and do damage.
I have switched to PB and keep my loads at 5K PSI and use it year round. One ounce and around 1125 fps. Check the book and I think you might be happier.
Builder; I have never personally witnessed this, but I do believe it is something that can happen & your post is spot on. There is some pretty reliable speculation that this was a likely cause of some of the bursts in the early days of smokeless powder which occured a ways down the bbl & it was almost positive the bore had not been obstructed. Primers which had been adequate for black were not hot enough for the harder to ignite smokeless. Seems there may be just enough ignition to start the charge moving with full ignition taking place late. The projectile itself thus becomes an obstruction to the now rapidly moving gasses. It is a well established fact that rapoidly moving gases against a stationary obstruction can burst a bbl & I see no reason the same could not occur against a slow moving one. For all these reasons for the last 25+ years I personally do not load loads with manual pressures lower than the 6-7K psi range. For pressures lower than about 8.5K I do not use powders slower than Green Dot, PB or eguivelent. Guns having minimum chamber wall thickness I generally reserve for only moderate loads of BP. While we certainly don't always need max everything I think many go overboard in the opposite direction & just may be putting their guns at an unneccessary risk in the process.
I'd be happy to post your pic for you if you'll send it to revdoc2@cox.net by jpg attachment.