I used the same syringe as Steve does. You don't even want to try prying their mouth with that. You can break teeth and/or injure the mouth. I used that syringe, but not to open the mouth. For that, I take a smooth glossy matchbook cover, fold it, and use the smooth fold to get the mouth open. Once the cover is in the snake's mouth, it's easy to slip the syringe tip in over the top of it. Then move the matchbook cover out of the way. Not exactly easy, but no injuries that way. And be careful with the syringe too. The tip only needs to go just to the back of the throat. Don't force it down.

Don't use that monsterous syringe you have. It's way too big. You only need a small 1cc/1mL one since doesage is probably just fractions of that. The 1mL will allow you to measure in 0.01 mL increments. This is how I gave Big Bertha her baytril suspension. Her dose was only 0.04 mL, otherwise known as 4 units on a 100 unit, 1cc syringe.

Don't confuse the doseage. Don't confuse 0.01 mL for 0.1 mL . (that would be deadly) The former is only one of the tiny marks on a 1 mL syringe. 1/100th of a full 1mL syringe, not 1/10th! Way better to have the vet measure the doseage for you in a 1mL syringe with a removeable needle. That way you can inject the dose into food, or take off the needle and give it orally directly.

Be very careful and good luck!