I started trying to pull mine apart to upgrade the spring a few months ago but couldn’t get it to split apart, I was worried I was going to break it and didn’t have my pry tools on me to open it up properly without breaking it so I gave up. felt like it it was glued almost
whats the best way to get it apart?
Remove the grip and pump handle, take out all the screws, take off the barrel cap and start pulling the two halves apart from the barrel end. You definitely don’t need to force it, comes apart very easily. There’s a link to LG’s teardown at the bottom of the OP. 
Sounds like you may have missed a screw somewhere if yours was being difficult.
Sounds like the barrel may not be seated properly in the collar or maybe you’ve got some flashing around it. 
Mine handles LDT Heavy Milkies no problem and if anything they’re softer than pinks. Had a chat with a few peeps about why these seem to run so well at high FPS with softer gels… might be the larger cylinder and a less violent air delivery, maybe the way the nozzle seats in the collar… dunno, but whatever it is, I ain’t complaining.
Finally something I can use up my stockpile of heavy milkies in 
Sometimes the current trend of making gels a little smaller means they don’t work so well in the older blasters. I know that Duck’s Nutz gels are too small for a lot of my blasters.
Watch the low guido video above.
He goes through a slow, detailed breakdown.
Especially, dont forget to remove the upper barrel shroud.
There are 2 screws in there…it wont come apart if they are still there…