One thing I forgot to mention,
The Remington "promo""Dove and Quail loads" are actually about 1/16" shorter than a regular 2&3/4" shell and everyone elses promo loads.
I'm not sure the reason for this,it could be to discourage reloading (that was how I found out they were shorter!) or it may be to use a cheaper shot cup vs. a cushion wad that is longer.
One other note on shotgun shells,the promo loads are usually higher pressure loads than the regular priced ones.
It could be the use of the shot cups,cheaper (and usually dirtier burning ) powder,or maybe the grade of plastic in the case takes more force to open the crimp.These are all theories of mine,I'm not really that smart!
And I do have headspace gauges,chamber reamers and long forcing cone reamers too,if needed.
Hope this helps,Robert.