The Daisy model 21 took .175 BB's, today's BB's are .177. The model 21 is a rare and valuable double barreled air rifle. They were made between 1968-72. An average value for one in good shape, and still working, is around $400 to $525. In like new condition it is worth $800
Personally I would not play with it or damage is in any way.
I would contact Daisy customer service See the link below.
I use a Daisy Red Ryder BB Gun.
The Arrow household model jt-21 staple gun can use either 1/4" or 5/16" Arrow staples. The model jt-21CM can also use 3/8" Arrow staples
.410
Depends on your skills, size and parents.
In 1947, the steel shortage forced Daisy to use the aluminum lever.
A Daisy Buck BB gun can potentially kill a bird if it hits a vital organ or causes significant trauma. However, it is not recommended to use this type of gun for hunting birds as it may not provide a humane and quick kill. It's best to use appropriate firearms or air rifles for hunting birds.
Value of a gun is based on make, model and condition. You gave use year and caliber.
Depends on the make of gun. Some will not HAVE a model number, or it will not be marked on the gun. The .357 Magnum has been around since 1935. Even S&W did not use model numbers before WW 2, and Colt used names, not numbers.
22 Long Rifle
I can not find any information about a daisy model R6. In fact as far as I know Daisy dose not use this type of numbering system for any of their air guns or rifles. However Beeman makes a model R6 .22 Cal Air Rifle. Could this really be a Beeman and not a Daisy? If it is, then state the condition of the rifle as Poor, Fair, Good, Very Good or Excellent so I can give you an estimate of value.
It's uses size .12 for best results.