You do mean pellet rifle, not pellet gun. The Phantom is a rifle.
First of all not all Wallmarts carry the same air rifles in every store let alone every state. But I can help you with this information. The Phantom is a .177 caliber rifle that is rated at 1000 Feet Per Second (FPS) I suggest looking for a rifle that has a higher FPS ie: 1200 FPS or a .22 caliber rifle that shoots close to 1000 FPS. A .22 at 800 FPS will be a bit slower but it is a bigger pellet and will have more knock-down power than a .177 pellet at 1000 FPS. Don't confuse Speed with Power.
Think of it this way. If I shot a 1/4 piece of plywood with a .177 pellet, I would make a very nice dent in it. If I shot the same piece of wood with a .22 caliber Pellet at 900 fps I would most likely make a hole most of the way through it. Why Because the .22 is a much heaver pellet.
The ruger nighthawk
As far as I know the Crosman Phantom is not a BB gun but a pellet rifle. If you want to see the parts list for the rifle then see the Crosman link below.
Daisy, Crosman, Remington and Beeman
See the link below for the Owners Manual. Read the section "Adjusting the Trigger."
The Crosman Recruit is a pellet rifle not a pellet gun. If you want to see how the rifle is assembled then see the link below for the diagram.
The Crosman model 150 was made between 1954-1967. It is a .22 cal pellet pistol.
The Phantom is a single shot, single break barrel Pellet rifle rated at 1000 FPS that cost around $90. It is a true pellet rifle. Deigned for target and hunting. The Daisy 901 is a combo BB/Pellet rifle that is a 10 pump for a maxim 750 FPS. and cost around $63. Designed for plinking and fun. Personally I have never been a fan of Combo rifles ( But that is my opinion )
The Crosman 1088 Pellet/BB is rated at 400-430 FPS
Crosman offers a service to locate a repair center for their older guns and rifles. Click on the link below and then at the bottom of the page click on "Find a service center" it will direct you to someone who can rebuild your Crosman pellet gun.
It would help if you stated the model number. Crosman made several pellet rifles for Sears. You need to provide more information.
See the link below for the parts list and phone number for Crosman.
See the link below for the Owners Manual for the Crosman 1077 air rifle