I shoot a Trojan 20g and a VH 20g and use factory shells in both. Fiocchi, Nobel, Remington, RST, etc... I also reload 20g, both 2 3/4" and 2 1/2" and have some good loads that I've used and never had any issues with factory or reloaded ammo.

Here's a load that's listed on the Hodgdon website. It's for 20ga 2 3/4 " Cheddite but I use it for new Cheddite 2 1/2 " hulls with a roll crimp. It all fits in perfectly. 20ga 2 1/2 new Cheddite hull , Cheddite 209 , Fed 20s1 ,Universal 17.0 grains , 7/8 oz , 20ga overshot wad , roll crimp , 1200 fps , 8900 psi.

https://www.hodgdonreloading.com/

http://www.alliantpowder.com/reloaders/default.aspx

Look here for loads.

If you remove your stock, properly and carefully, and check the inletted head to see if it's good wood or if it's soaked with old gun oil, that will give you a good idea on the condition of the stock. You can always do a glass bed reinforcement or have a smith/stocker do it for you if that would alleviate any concerns you may have.

2 1/2" Cheddite hulls
13.2g Green Dot
SW 20 or Sport 20S BP wads
3/4 oz shot

for a spreader load I use the BP Brush Wad and you can add an X-Stream Spreader insert on top of the brush wad to really open the pattern up for close work.