While a throw in conversion kit is enough for me to hit up to 100 yards, I started experimenting with some Aguila SSS ammo (Sub Sonic Sniper 60gr subsonic). The 60gr rimfire stabilizes well in my 1:9 barrel and quite accurate, beyond 100 yards accurate. Still the wrong bore size but still almost as good as my dedicated rimfire upper.
I highly recommend a premium firing pin because you will break yours, just a matter of time. All my kits run well dropped in as is unless I go full auto and then there is some more parts and tweaking going on.
My dedicated rimfire has the CMMG rimfire metal ambi charging handle which is short and has a neck that is almost all solid to block gas, cut port ejection door, moved brass deflector, forward assist accessory on the bolt (which will probably only get me in trouble one day as rimfire gets dirty fast, especially when suppressed and I am tempted to use the forward assist instead of cleaning) and rimfire magazine catch. Some people put a special plug into the FA so it looks normal yet non-functional. You can get the gas blocking insert for the standard charging handle from Borebuddy, including the firing pins and a lot of other nice upgrade parts. I don't bother with special parts on my throw in conversion kits except to upgrade the firing pin when the OEM breaks.
If you are going full auto or trying to use it with an FRT trigger, Borebuddy has an adjustable auto sear trip now so you don't have to bend yours to time your carrier correctly, as well as an adjustable anti-bounce weight with removable weights that can be configured in multiple weights. You need both the auto sear trip and anti bounce weight to go full auto or FRT. As you can see in my posted videos above, they work well in full auto when properly configured (and the ones in my video have no special parts or tweaking, they happened to work for me quite well)