Looks like you alreadya nswered your own question - having the bullet stick in the rifling is a sure sign of them being too long. Bolt will not lock up, preventing full battery and hence, firing.

One respondee said to check the OAL as 2.55 is too long for mag length - that's for sure! The 80's can - and are - fired successfully in AR's (service or match) at the longer range line (600 yards) but as dingle load only. Depending on throat / chamber distances, I would start at 2.45". You probably want to be .010 - .015 off the lands anyway for best accuracy. My newly barrelled service rifle is loaded at 2.45 jsut to be sure, while my spacegun handles 2.50. You can use a Stoney Point or simialr emasuring tool, but 2.45 should be very safe.

Eric