First thing I'd check is the Cartridge Overall Length (COL). Use a dial caliper (if you don't have a dial caliper, get one. It is a "must have" tool for a handloader) to measure the round from base to tip and compare that value to the one published in your load manual for the bullet you're using which is the SAAMI spec for the cartridge. If the COL is longer than published you might be jamming the bullet into the rifling which will make the bolt hard or impossible to close. This condition can also cause dangerous pressure spikes so don't fire any cartridge in this condition!!

If they are too long, adjust your bullet seating die and reseat the bullets deeper to match the COL in the manual (but not any deeper, because this can also cause pressure problems). If this doesn't identify and fix the problem, then you probably need to FL resize the brass, (do you have a bullet puller?) at least enough to bump back the shoulder but I'd probably FL resize them back to SAAMI min spec just to be sure they'll work. You can always test chamber the sized brass to see if they'll chamber.

Good luck,

Mike