Hey Buzz,
Welcome to South Central Pennsylvania. I was born in Lancaster, grew up in Middletown, and, from 1 June to 15 September, I love this place. The other nine months are just too cold for me, and I would rather be down in the Southwest somewhere in the desert living in our camper. My wife and I will head for Florida duing the last week of this month, and we will be there for about 6 to 8 weeks.
It sounds like your 1200 was a good buy. I don't know why your 5th round goes in hard though. Have you looked in the magazine to see if there is any kind of a short plug or something else interfering with the loading? No clue as to what the spiral grooves are in your barrel either. I would also guess that mine is probably newer than yours, but mine does not have a ventilated rib. It is just a plain real long heavy barrel. My understanding is that the 1200 was the Winchester replacement for their Model 12, and it was considered a lesser gun than the Model 12. I don't know if it was not as good as the Model 12, but the Model 1300 that replaced the Model 1200 certainly was not an improvement in looks. I sold my old Model 12 and kept the 1200 - simply because the wood on my 1200 looked so good.
If you would like to blast some claybirds in the back pasture sometime, give me a call at (717) 432-8732.
Best wishes,
Dave Wile