Do not fly that load in anything you care about. Best use in saucer,where delay time does not matter.
Problem lies with " chuffing" on pad or inability to light/come up to pressure quickly. During this phenomenon, the delay continues to burn. After several tries you have a very short delay time & ejection charge may go off while rocket under full thrust.....gets ugly.
Some times the motor may chuff, just as rocket clears the rod/rail, losing pressure, causing rocket to slow and change direction violently, then come back up to full thrust going horizontal or whatever direction rocket took during the chuff.
Yes you can enlarge the slot, cut off/sand the swollen end to fit,but in the end,you have an "iffy" motor. I have had many over the years ......some worked....others did not horribly. Now I use them in saucer 's where no damage can be done.
Then again it may fly perfectly....just letting you know from experience [15-20 old G-motor flown] it's a crap shoot, with no guarantee's.