You don't unscrew the barrel off the model 99 you unscrew the shot-tube inside the barrel. Look closely at the end of the barrel you will see that it has ridges around the end. Grab these and untwist the very end of the barrel. It will come out and you will be able to pull out the shot tube.
See the link below for the Owners guide for the model 25, it uses the exact same barrel and loading system as the model 99.
You just unscrew it off the barrel
First, unscrew the magazine tube cap, located at the end of the forearm. Then pull the action back to about half-way, then you should be able to pull and jiggle the barrel and forearm free. To reassemble, slide the barrel and forearm back on, and pull the action back until the barrel slides into place, then rescrew the magazine tube cap.
you just unscrew the muzzle brake and replace it with the silencer
Unscrew cap from end of plug chamber .Take your barrel off there will be a little tin cap at the end of your plug barrel take it out to get to your plug
well you unscrew the screws and gun off parts of the barrel you should be left with the inner bit where the bullets go threw!
By designer are you asking what Model it is? If so, the Model can be determined by the serial number, which is located on the barrel flats and the forend. You have to take the barrel off the receiver to see them.
If the co2 cartridge is full unscrew the back slowly until all vapor is gone, then just unscrew the back all the way off and it will slide out.
I can't exactly identify this model but I believe I know what it is. Both Daisy air gun and Crosman air company made pellet/BB guns and rifles for Sears under the JC Higgins name. All the Crosman models started with Sears model #126. All the Daisy models started with Sears number 799. Daisy made a 1894 model for Sears and the number was 799.19052 it really was a Daisy commemorative model 1894. It looked like a Winchester 3030 it had an octagon barrel. If this is your rifle, hopefully it is then the standard Daisy model 1894 is worth $50 to $100. If this is the model 799.19052 Commemorative model with gold plated finish it's worth $200 to $250. Because your number is only one digit off, I think it's a standard Daisy model 1894. This is all a best guess it I have the right rifle or not.
It would help if you stated the model.
Pull down on the front of the foreend. It snaps right off. Open the action, and the barrel lifts back and up off the hinge in the receiver.
To take apart a Stevens Model 311 double barrel for stock replacement, first ensure the shotgun is unloaded and the safety is engaged. Remove the forend by pushing the release lever and sliding it off the barrel. Next, locate the stock screw at the rear of the receiver, unscrew it using an appropriate screwdriver, and then gently pull the stock away from the receiver to detach it. Be cautious to avoid damaging any internal components during this process.
It is a Savage/Stevens Model 94, and the barrel has been cut off. Value is minimal.