I had two .17 Ackley Hornet barrels for Thompson-Center TCR-87's and TCR-83's. The both shot fine with 20-gr Hornaday V-Max bullets, IMR4227 powder and Remington 7-1/2 primers. One of them would often shoot less than 1/2 MOA groups. I had a third barrel made up shorter and threaded for a silencer. With the same loads it shot groups slightly over 1.0 MOA. I decided to try CCI BR-4 primers on some of a batch of fireforming loads with the same powder and bullets. Fire forming loads in the other two barrels don't shoot very good and the cartridges don't even look good as they are lumpy and not even symetrical where the new shoulder will be. However, in the new barrel with the new primer they shot slightly less than 1//2 MOA. It amazes me how much difference a different primer can make. I am thinking the loads with fully fireformed cases should also shoot accurately.

As the saying goes: "each rifle is a law unto itself"
Any change in components can cause changes in performance. both good and bad. The improvement in performance in the new barrel is no guarantee that it will work in the old barrels. The only way to find out is to shoot them. Which is kinda what we're after, right?