There is a slide on the right side of the barrel. Push it forward and hold it while you put the BB in the loading door on the right side of the firring breech.
This BB rifle, not gun, was made for Sears by Daisy air gun Co. In reality it is a Daisy Model 1894 carbine, octagon barrel. it was made between 1969-73 it was a "Replica Centennial Rifle."
1988-1991.
Best to ask a gunsmith for assistance.
Any air gun made for Sears that starts with model 799 was made by Daisy. Your number 799.190552 I think is incorrect I think it's really 799.19052. I have no listing for a 799.190552. But the 799.19052 in very good condition is worth between $175 and $145 The 799.19052 is a Daisy model 1894 Carbine, Winchester style, Octagon barrel. Made between 1969-1973.
Please explain how it can have an octagon barrel and no barrel. I can't find any series 799 in the cross-over list for Sears firearms, so maybe it is a bb gun, but I have never seen a bb gun with an octagonal barrel (or with no barrel). I have a Sears & Roebuck model 799.19052 air gun. It has an octagonal barrel. Sounds like your gun is missing the shot tube. Sears contracted with Daisy Air Guns to make these '1873' "Look-a-likes" from Daisy's standard 'Spittin Image' line of 1894 Carbines. They changed the butt plate to a curved design, shortened the forearm slightly and added a "brass" cap to it, and put an octagonal "sleeve" over the existing 1894 barrel. Neat looking little air gun. If you can't find the proper shot tube one can be made from the right sized tube and an end "plug" to hold it centered in the barrel.
the barrel cant be replaced. the barrel is plastic with a steel shell
This particular model was made by Daisy air gun co. It's a 1894 carbine. It was made for Sears between 1969-1973. It is the 1894 Commemorative model
20 USD
This rifle is a Daisy 1894 made for Sears.. It was made between1969-73. It's a commemorative model. It's marked Replica Centennial Rifle Crafted by Daisy or just Crafted by Daisy. In good working order it can be quite valuable. Please state the condition of the rifle so I may give an estimate of value. Poor, Fair, Good, Very Good, or Excellent.
You will find it on the barrel directly in front of the sight.
Daisy offers a free service to tell you more about your Daisy. You can also write to them and see if they have a parts drawing for the rifle (See the links below)