In this study, no one saw rubber cores of the 800 or so samples. With the 18G needles the cores they found were smaller than the internal diameter of a 23G needle. The only reason I started researching this was because I saw some floating around in the vial, then I actually saw the grey rubber floating around in the syringe and I would not consider my eyesight that great so they were of pretty good size to be visible to me so I pulled up my florescent magnifier. I did have one instance where the syringe stopped as I was injecting so I pulled out, swapped needles and continued with no issue. (not sure if that's the best course of action but)
Here is the article I referenced:
Avoiding unconscious injection of vial-derived rubber particles during intra-articular drug administration
Here is a technique to reduce coring but I would suspect you'd want to use the larger diameter needle to draw:
Proper Injection Technique to Prevent Coring - Innovation Compounding
My next leap of logic, and I'm internally debating this. Since I'm clearing the needle by pulling air back into the syringe before I swap needles every time I inject, (every 4 days), I'm wondering if it would be wise to come up with a way to simply pull the grey stopper and pull directly from the vail by totally bypassing the needle through the stopper. ??? To get the last .3 to .4 mL's I do that anyway.
My logic here is that I'm pulling air into the syringe every single time anyway. So by pealing the aluminum off the vial, un corking, resting the grey cork on an alcohol swab, pulling test with 18-20G needle to minimize time, recorking... thinking this would be a bit more air exposure but zero chance of injecting tiny bits of rubber into my body and with the percentages referenced, I'd have 9 times per year with rubber in the syringe from a pure statistics point of view.
This also makes me wonder if these tiny bits of rubber being injecting into people have any direct effect upon other medical issues such as increased stroke risks, etc... Think about folks with diabetes, they do this every day with needles small enough to guarantee they're getting tiny cores every other time.