250-500cc '11 wr300 need to repack silencer, but can't get either end off

So what's the trick to getting either the front end piece or back end cap off of the silencer off so I can repack it? I've removed the 4 screws/bolts at each end (left the rivets in place). With a rubber mallet I can push the end cap in slightly, but can't pull it out (was trying w/a pipe spring puller). I can also get the front end piece to wiggle slightly outward, but again can't pull it out. I only need one end off. I assume each end is sealed. Do I need to apply heat to break it? Use an exacto knife? What's the trick? Will I need to reseal it when done? If so, will black rvt silicone suffice? Thanks.

I apply heat then pull pipe out of canister some tapping with mallet may be required,pull hard

theres a rubber oring seal & silicone in the stinger end-real tight fit as youve found out! i put mine in a vice with alloy clamp inserts or timber then using a mallet & some bits of timber or punches(go easy) tapped the cannister off the core. this is for the AUS version silencer but yours should be similar just with a S/A in the tip i think(ours are welded tips only-no rivets-remove core from stinger end). the ridge where the mounts are is raised a bit so best to start there & work ya way around. just tap it off evenly. tight to get back on too. heat may damage the oring id reckon. didnt bother with silicone when reinstalling because it was such a tight fit & figured a bit of spooge & carbon build up would seal it anyway. no probs so far oh yeah like kx3089 said pull hard, 2 man job maybe, one tap one pull. haha