While I am uncertain whether Winchester made a solid frame Model 12 shotgun, I know that Model 97s were made as solid frame at least through World War I. Since the Model 12 locks breech bolt to receiver and Model 97 locks breech bolt to its shell lifter (I don't know its correct nomenclature) that is anchored to receiver - more substantially than Model 12's lock-up - what sort of accuracy might be expected from a circa 1950s Model 12 and/or 97 installed with rifled barrel of satisfactory wall thickness using the general purpose slug load in John Taylor's African Rifles and Cartridges - that is, 12 gauge, 7 dram [equivalent], 750-grain bullet, 1550 fps, 6.0 [long??] tons pressure. I anticipate currently manufactured high brass cases will accept the loading.

While load's pressure is nearly that of proof load for 12 gauge shotguns, the two Winchesters are egregiously over designed. By its nature, such a load would be used "sparingly."

Winchester's solid frame version of the Model 12 is known as the Model 25 - made in the mid 50's in 2 3/4 inch only.

My thoughts if one is going to shoot hot slugs loads out of a rifle barrel.

Buy a more modern shot gun that set up for it.

They can shoot really nice groups.

I would agree that you need to go with a more modern design. My preference would be a Winchester 1200-1300 with a rotating bolt head that locks directly to the barrel extension. Others in that category are Benelli and Stoeger pumps. Some makers use a set screw to firmly secure the receiver to the barrel extension. Usually through the left receiver wall on a right hand gun. Remington uses this in their 870 rifled pumps.

Accuracy: There are Youtube videos of exeptional groups at up to 250 yds. I've seen 2-3 in 100 yd groups with Remington premium Sabot rounds.

Are you using cast lead bullets? Paper patched or plastic sabot? Sounds like you envision a close quarters emergency stopping rifle?

Ithaca deerslayer

Yes. The rotating bolt head is a very good idea for this application. Strong.

I've owned a Winchester 1200 pump since 1972. I when I moved to NH, I bought a rifled slug barrel for it, since most of where I hunted was shotgun only. Shoots better than minute-of-deer, maybe 3" groups.

As Bob said, it is a strong, rotating bolt design and takes 3" magnums without issue.

If ever I have to sell my guns, it will be one of the last to go..