Hmmm...I shoot the same ammo from my 1911 pistols..never noticed any sparks flying from the ejection port.
I have had boxes of Winchester/USA ball ammo that left huge amounts of unburned powder in and on the gun..and on me..
My guess is it's just the particular batch of ammo.
I had a weak..almost squib round fired from my 9mm Hi-Power that noticably flung sparks from the empty upon ejection the other day...and I've noticed the phenomenon from smaller blow-back pistols before.
Some Ultramax 'Cowboy' .45-70 ammo I was shooting from my ancient trapdoor rifle was leaving bunches of unburned powder in the action and barrel. I thought it was some sort of 'filler' they used to reduce the load..but it was powder. I scraped some out into a tiny pile..and it would burn. You would think 30 some inches of barrel would burn all the powder..but I guess not!
Try different ammo..and I bet the phenomenon goes away. It's just the batch of powder Remington used for that particular batch of ammo.