They are basically the same locking block/receiver, except that the newer models are made exactly the same, due to modern machining technology. The older models were all hand fitted and thus the barrels are not always interchangable without some fitting.
The top lever release pin has been moved.
The triggers are the same except that the hammers on the newer guns are machined all the way across for the under barrel and the older triggers won't work on the new style firing pins unless the face is machined like the new ones. The firing pins have changed accordingly.
The only way the Comp I isn't as good as the newer style, in my opinion, is the forend design has been changed as the older models were prone to splitting.
I believe the older case hardened receivers are stronger than the new models.
In the other century I picked up and had the honor to try a number of the ol' Comp 1 single barrels. I never met one that I couldn't shoot well and shouldn't have bought or replaced but could never rationalize the what, $700 they were at the time? Oh, how I wish I'd bought a truck load of them now. I did have a time when I had to be out of trapshooting for several years and it was the Comp 1 I wanted to find when I returned with any seriosity. My looking led me through a number of "other" P guns and they all felt like some part of a Oil drilling rig in my hands; never got into the MX8 O/U though. I finally reached the next best thing with the KS-5 Spl. and can see no reason to ever replace it.....breakemall....Bob Dodd
Interesting comments...thanks, Guys! I recently got a Super X1 from Ruck to get back into the trapshooting I never really got into, as I am basically a Skeeter, but I had to give up most of the clay sports some years ago due to on-duty injuries that played havoc with some of my joints for years. It is a great gun, and I love the old Winchesters. I find trap fascinating, and I know that sooner or later I'm gonna want an o/u...the Pirazzis intrigue me. I saw a nice one (90-95% I'd guess) with good wood the other day for around $3500.00 which I understand may be a little high.
I own two--a trap and a skeet--both bought new as ithaca imports-have shot thousands of rounds with both and wouldn't take a farm in ga. for either. Replaced one top lever, several leaf springs and had ribs on both guns resoldered by giacomo. These older p guns are a little lighter than the newer p guns and can have a bit of a kick if they don't fit,but I have NEVER,EVER, found a gun that balances in the hands like either one of them. They feel alive in your hands like very few other guns.
I bought one for my wife,it is silver nitite frame and very pretty wood,I had to replace the cocking linkage in at 400.00 other than that the gun is an absolute peach,it'll never leave this house until no more shots are fired.Every bit the gun the MX8 is,in my opinion,I have one of those too.Jack
Have a Comp IV (TM1 with racing stripes and CT) Ithaca import. 34"
730 bore. Adjustable soft comb and adjustable butt pad. Bluing and
wood excellent. Locking lever to right. 14 1/2 LOP. $2375+shp.