I bought a Rossi Trifecta .22/243 Win/20 gauge combo & have had no unforeseen accuracy problems with it. The .243 Winchester cal. bbl generated 4""-10" groups at 100 yds as other folks have noted previously which is nothing new with me in breaking in & accurizing any new rifle in my 48 years of shooting, hunting & gun collecting. I initially use factory ammo which is factory-loaded to the max, generating inpredictably large groups while sighting in the rifle...then reload handloads to carefully tailor ammo which results in tighter groups at 100 yds-200 yds at the range. This accurizing process has worked for me for the past 48 years on my gun collection of .22cal LR, .22cal WMR, 22-250, 223 Remington, 25-06, 30-06, 7mm Remington Mag, 7mm Weatherby Mag, 7.62 NATO (.308 Winchester), 300 Winchester Mag, 375 H&H Mag, 416 RIGBY, .416 Weatherby Mag, 458 Winchester Mag, 45/70, 30-30 & .50 Cal BMG...& now a .243 cal Winchester.
I usually start with loads 2-3 grains above minimum with lower muzzle velocity (100 fps-200 fps less than max for the bullet size recommended in the reloading manual) fire 3-shot cold-barrel groups at 100 yds until a have a very tight 3-shot group. Every rifle has a "sweet_spot" load where maximum accuracy + optimal
muzzle velocity is reached which then becomes my hunting load. On my Rossi Trifecta .243 Winchester, I'll be starting out using 43.0 grains of RL-19 powder using large rifle CCI primers, Winchester .243 caliber brass + 100 grain Sierra BTSP bullets. I feel very confident on getting my .243 Winchester cal 3-shot 100 yd groups down to a MOA (Minute-of-an Angle) or less, as I have successfully done with all my other hunting rifles. The only exception has been my .375 H&H Magnum O/U Double Rifle, 470 Nitro Express Side-by-Side Double Rifle & miscellaneous semi-auto military rifles...My double rifles are "regulated" to shoot 1-3" 2-shot groups at 100 yds for dangerous African big-game & my military semiauto rifles lack the inherent accuracy of my bolt-action/single shot hunting rifles to group sub-MOA at 100 yds.
---by a retired Nam U.S. Navy Hospitalcorpsman FMF 1st Marine Division + U.S. Army OCS Field Arty Forward Observer/Battery CO vet.