On a Mossberg Maverick 88 All purpose, can slugs be fired through it?

You can fire any shotgun shells through it that are the correct gauge and length. You barrel should say what that it. If you have a 12 ga., it should say something like "12ga, 2 3/4 inch and 3 inch shells". The maverick is just a mossberg 500 without any frills. You can shoot any kinds of shotgun shells you want. Slugs are fine with that choke, but if you are planning on shooting them often, you could probably go to an Improved Cylinder (IC) choke when you can afford it. It is a bit larger, so the slug will deform less as it goes through, hence gives you a bit better accuracy. It should also kick a bit less with slugs that way. And for the record, you don't need to go get any other shotgun. All of the regular mossberg 500 parts fit it, and it will last you for decades. Good luck, and have fun.