The Sheridan Silver streak takes a 20 Caliber Pellet. You can find them at a good sporting good store or online (see the link below).
Remember a heaver pellet will fly slower but it will fly straighter and have more "knock down power" than a fast light weight pellet that is more affected by crosswind.
Ridan Products? do you mean SHERIDAN Products. What do you want to know. Also Sheridan made pellet rifles not pellet guns, and yes they are still produced today. What is your question?
No. a 177 is a 4.5mm pellet. A 5mm is a 20 cal pellet. A 5.5mm is a 22 cal pellet Don't try it in the wrong airgun.
diameter
Somewhat. The .25 cal is just bigger and hits harder. Other than shape and air pressure behind the pellet, the size and weight of the pellet has a effect on the accuracy. OKAY look at it this way. (Pellets come in different weights.) a lightweight pellet will fly faster and farther than a heavy pellet. BUT it is more effected by crosswind than a heavy weight pellet. The Heavy pellet will fly straighter, slower and have more knockdown power than a lighter pellet. So a .25 cal pellet is heaver and slower than a .22 cal pellet but it has more impact and a little more accurate than a .22 cal pellet. PCP rifles come in different sizes. like .177, .20, .22, .25, 9mm, .357 cal 45 cal and 50 cal. Hitting a target with a .177 cal is like hitting it with a BB, but hit it with a 50 cal and you rip a huge hole in the target. The .177 will fly a lot farther but the 50 cal is a destroyer. I own both a .22 cal and a .25 cal Marauder. along with several others.
The Sheridan Silver Streak is a 20 cal pump air rifle. To get an estimate of value please state the condition of the air rifle. Is it working? Is it in poor, fair, good, very good, or excellent condition.
Given the right circumstances and shot placement, any of them
No it will jam in the barrel.
What condition is it in. Without more information it is not possible to give you an estimate of value.
It was not designed for 25 cal ammunition.
16 years
I assume that you are asking about the .20 cal Sheridan C Silver Streak NOT the C9 Silver streak. (It's worth more.) New in box: Excellent condition $185 Very Good $160 Good $120 This is just an estimate.
Cal .177