Jug choking works well if you do it 5-6 long instead of the 2 Ive seen tried which does very little to tighten a choke. Not enough bore for the shot to open up so you can squeeze it tight again.
I have had one gun jug choked and had several we could not do it because the barrel walls were too thin. If you have a set of barrels, which are .020s 4-6 from the muzzle, you dont have enough metal to work with. One set of barrels looked great from the muzzle end with .030-.035 metal to work with but six inches back they were .022-.026. The bores were straight but the exterior was struck thinner away from the muzzle. I wanted .020 choke added but taking .010 per side away would have left them .012 and .016. Time to measure wall thickness and let that be your guide.
I guess a card or wad will pass through the choke area, jump across the back bored area and fit snuggly down the rest of the bore. On the way out you might get a trivial amount of blow by in the back bored area but it should have little effect on the pattern. Those guns with termite holes along their muzzle, proported to clay target hunters, seem to suffer no ill effects with that gas loss. The Russians bored a lot of their Olympic Skeet guns that way but the fad never caught on here in the US. Tulia chokes was the name as I recall. Two versions, one with a Olympic-wide muzzle type and straight choke type with the intent to keep chokes tight and eliminate all fliers
