I've had a recurring problem with my Pedersoli 44/40 'Lightning' pump. The odd round won't chamber fully :ummmno:
I have previously trimmed all brass to a specific length of 1.295" (slightly shorter than spec) so I was confident that wasn't the problem so I started to look at my powder coated bullets.
When cast they measure 0.430" exactly and when powder coated 0.4315". When loaded into Winchester or Starline brass there was no problem, but the problem persisted with Remington-Peters brass.
I found the cause in the brass, R-P was a full 0.002" (0.001" each side) thicker wall thickness than the other brands. The solution was to size the powder-coated projectile through a 0.429" sizer. Was suprised to find that the powder coat itself remained unbroken and the rifle fed without any further problems.
Similar thing happens with my Winchester P14 303 British, have been using a 0.316" size die to crimp on 8mm gas checks and not size the projectile. Again some rounds are difficult to chamber without running through my 0.314" sizer.
So there you have it, if chambering is difficult remember that powder coating ADDS 0.001- 0.0150" to the diameter of the bullet.