We have our own tubes made out of heavy walled borosilicate tubing (Pyrex), and when we first started making them, I broke four tubes at the injection nozzle, because of the embrittling effects of the R-600 butane refrigerant chilling of the glass.
We changed the injection end design to maintain uniform thickness and a full radius on the closing end, so as to more evenly distribute expansion and contraction stresses.
When the glass is embrittled by temperature, it doesn't take much of a wiggle at the injection port to flake off a piece of the glass, unless the injection port is designed to minimize effect.
A stainless turkey baster doesn't suffer from the same pitfalls, so you might check it out. If you are willing to keep it free of oxidation, copper also works well without breaking.
I use all three. Hee, hee, hee............