I am changing the muzzle device on my Arsenal SAM7R and the muzzle detent is stuck flush in the front sight. It has had a Lantac Drakon (with crush washer) on it since I bought it, and has probably 3500-4000 rounds through it.

I'm not sure if the crush washer caused this issue or what? The detent has about 1/16" of movement and feels springy, so I don't believe that the spring failed. I soaked it in Kroil and smacked it with a mallet for about 30 minutes and was able to get it to protrude about 1/16" out of the sight, but it still wont come all the way out.

Is there anything else I can do? Is it a pain in the ass to remove the front sight pin and push the detent out with a pick? Are Arsenal front sight pins tapered? Sorry if these are stupid questions, but I'm not having much luck with finding specific search results .

Any advice would be appreciated. Thanks in advance!

Try some heat. As in hot enough to burn skin. Then smack it again hard with a punch

I am guessing it has a lot of residue in there stopping it from springing [pun] out. A little heat might help with more penetrating oil ,keep working the movement you have now . I would stay away from a hammer at this point,it is kind of stuck in right ?

Mine did same thing. I sprayed some CLP in it and shot it without brake on to jar it loose. Now moves fine

HEAT AND SPRINS DON'T MIX .

Sounds like it was staked - look around the plunger bore on the face of the sight base  for indentations. I guess even though you managed to get it to come out a little, it's still not free. If you have it out 1/16", you don't need much more. You can also punch out the front sight base pin to remove the plunger and spring so you can maybe do some careful filing around the face of the bore if you find that its staked. Otherwise it sounds like possible firing residues and/or moisture have bound it up. Keep using a good penetrant on it and keep moving it. You might get some brown oil out of it if its rusty, and it might need a new spring.
BTW, upon re-reading, sounds like you are trying to actually take it out without removing the sight pin? You can't do that. If you have it out 1/16" with spring action, I think you should be able to index a muzzle attachment with it and it will hold it in place. A little bit more would be great, but it might already be all the way out - they vary.